Re: [Emc-users] Stepper, ideal pulses without feedback

[Nicklas Karlsson]

> Nicklas, when I built a pcb drilling machine some years ago, I found
> constant acceleration and deceleration to top speed worked best, as
> for the most part trying to go instantly to the maximum speed the
> motors are capable of results in lost steps.
> You will need a bit of experimentation to determine the rate and
> length of both acceleration ramps as it will depend on the mass of
> your machine and the motors and power supply you are using.
> 
> Ken.

Constant acceleration and deceleration to top speed worked best fit very well 
with physics.

Stepper motor magnets induce a voltage proportional to speed which limit 
maximum speed. Torque is about the same regardless of speed and there are some 
intertia.

Regards Nicklas Karlsson



> 
> On Sat, Mar 19, 2016 at 5:46 AM, Nicklas Karlsson
>  wrote:
> > I am planning to use a micro controller for stepper step pulse generation. 
> > I have considered to use an inverter card but special purpose stepper 
> > circuits are cheap so I use one of these instead. It should be possible to 
> > feed timer values then toggle should happen via DMA timer output compare 
> > values.
> >
> > Can anyone suggest how an ideal step generation curve should look? Constant 
> > acceleration up to top speed? Constant deceleration from top speed to zero? 
> > Or just stop generating pulses?
> >
> > Regards Nicklas Karlsson
> >
> > --
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Re: [Emc-users] Linuxcnc on arm

[bari]

RTAI patches the kernel with an interrupt pipeline and handler that can 
take over real time interrupts but drivers can still interfere with it.

Things used to be worse. Especially with integrated GPU's. We did lots 
of RTAI development over the past few years and we had difficulty 
building custom RTAI kernels with jitter (measured using only the 
latency test) <5uS on AMD APU's (with integrated GPU's) made in the past 
5 years. 5+ years ago people were having problems with boards with 
integrated graphics. Getting them under 100k uS was not possible without 
using an external GPU card.

We didn't touch any nvidia or Intel silicon but most AMD boards were 
under 25uS with integrated graphics.



On 03/16/2016 04:12 PM, Jcd wrote:
> So what makes the real time Linux like machine kit or for a regular PC. If 
> drivers can muck things up.


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Re: [Emc-users] Linuxcnc on arm

[Yanjun Luo]

Hi,
I think Raspberry Pi Module 3 is a good choice, I'll try it when I get a
board soon.

Regards,
Yanjun Luo.



2016-03-16 23:25 GMT+08:00 bari :

> The i.mx6 can easily run Linuxcnc. The issues that you'll run into are
> the high cost of the i.mx6 boards and getting the GUI to run fast
> enough. Some i.mx6 quads are under $20ea, but the boards they end up on
> tend to be priced closer to $100. Well above the price of a new suitable
> x86 board. The i.mx6 has integrated Ethernet so hm2_eth just might work
> and it also has PCIe.
>
> I considered making an i.mx6 board last year targeted for Linuxcnc but
> there isn't enough interest if the cost is much higher than an x86
> solution.
> http://openlunchbox.com/open-sbc/
>
> On 03/16/2016 07:17 AM, Erik Friesen wrote:
> > I have been doing some work with an i.mx6 of late, and wonder why the
> quad
> > couldn't do linuxcnc?  It seems there is some obscure reason I read
> > somewhere.
> >
>
>
>
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[Emc-users] Stepper, ideal pulses without feedback

[Nicklas Karlsson]

I am planning to use a micro controller for stepper step pulse generation. I 
have considered to use an inverter card but special purpose stepper circuits 
are cheap so I use one of these instead. It should be possible to feed timer 
values then toggle should happen via DMA timer output compare values.

Can anyone suggest how an ideal step generation curve should look? Constant 
acceleration up to top speed? Constant deceleration from top speed to zero? Or 
just stop generating pulses?

Regards Nicklas Karlsson

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Re: [Emc-users] Q re these Chinese 3 phase motors.

[Gene Heskett]

On Thursday 17 March 2016 22:57:06 Gene Heskett wrote:
Ping?

> Greetings;
>
> This one is a 1.5 horse, 8 amps nameplate rating, air cooled which at
> low speed isn't goping to work at all well anyway, and at 20 Hz drive
> I am quite dissapointed in its torque, 3 or 4 oz/in when the torque
> boost is disabled.  I can stop and hold it between thumb and
> forefinger quite easily.  Turn the torque boost, range 0-4,  up to
> 0.5, and the apply frequency to 50Hz, about doubles the torque but
> that would be of limited usefullness at a 20% duty cycle max is it
> heats badly, hitting 130F at the front bearing plate in about 7 or 8
> minutes just laying on the table spinning.  So I think its not going
> to be terribly usefull for g33.1 tapping unless I add another 10/1
> range between the motor and the backgear input the current motor
> drives. Reversing times are well subscond at 200Hz drive, so the added
> gear would seem to make up the missing torque.
>
> I've attempted to gain access to removing the collet but have failed
> as it appears to have a spanner hole equipt ring that may be setting a
> bearing preload, so I am hesitant to put a wrench on the collet flats
> and try to loosen it with a set of tru-arc pliers.
>
> Making a short stub shaft to put the existing drive gear from the OEM
> motor on the stub and chucking up the 1/2" sticking out seems like a
> bearing life shortener because of the amount of unsupported shaft
> between the bearings and the gear.  But that looks like the only
> choice if the collet cannot be easily removed.  That of course will
> need mount extensions to make room for the gear train.  All thats
> do-able of course once a suitable set of gears are in hand.  Boston
> Gear to the rescue I suspect.
>
> The front, also black coated ring doesn't seem to meet the piece its
> screwed to with some short 4mm screws, which when I inspected it
> first, was pulled up a bit lopsided with two screws quite tight and
> the third one quite loose leaving a noticeably uneven gap between the
> parts.  That spanner hole equiped ring on the rear of the collet
> prevents its removal, as if the hole in that ring is smaller than the
> spanner hole equiped nut. So it looks as if the spanner holed ring may
> be the first to come off, then this stationary part behind it next,
> but not knowing whats bearing preload, I didn't go any farther.
>
> Has anyone done that collet removal from one of these motors? And can
> guide me on the procedure?  I'd druther not make a $180 pile of junk
> out of it.

Would it do any good to put up some pix?

Maybe someone here would recognize it...

Thanks.

Cheers, Gene Heskett
-- 
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 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Stepper, ideal pulses without feedback

[Nicklas Karlsson]

> Hi Nicklas,
> 
> it should be fine to keep the step rate (velocity) constant between
> updates from the trajectory planner, assuming that it runs at something
> like 1kHz and the machine is not highly dynamic. Limiting velocity and
> acceleration in the step generator should generally not hurt and avoids
> stalled motors in case there is a step in the position command (which
> should not happen with LinuxCNC unless you mess around with the signals
> in HAL).

Then I will limit acceleration and velocity to avoid stalled motor.

I expect the magnets inside the stepper will induce a voltage proportional to 
speed and in such case this will limit maximum velocity.

There are some inertia both in motor and other mechanical parts which will 
limit accelaration. If available torque is approximately the same regardless of 
stepper motor speed a constant for maximum acceleration should be a good 
choice. There exist a possibility stepper motor maximum torque depend on speed 
but I have no idea about this kind of motor.

Regards Nicklas Karlsson



> On 18.03.2016 21:15, Nicklas Karlsson wrote:
> > It could be a good option so I do not need to have a large computer for a 
> > small machine. As is know it is more a question about how to ideally 
> > increases/decrease step rate for a stepper motor?
> > 
> > 
> > 
> > On Fri, 18 Mar 2016 16:05:31 -0400
> > John Alexander Stewart  wrote:
> > 
> >> Just FYI - about a year ago or so I purchased from Jeff @xylotex a BBBlack
> >> and DB-25 cape - ran my Unimat SL CNC'd lathe just fine (feeding a spare
> >> Gecko G540, 2 axes of which were unused)
> >>
> >> BBBoard from Xylotex came with LinuxCNC Machinekit on a little SDCard. An
> >> out of the box solution.
> >>
> >>
> >>
> >> On Fri, Mar 18, 2016 at 3:50 PM, John Dammeyer 
> >> wrote:
> >>
> >>> You might look at the Replicape and a BeagleBone Black.   There are 
> >>> several
> >>> other capes including one with a standard DB-25 parallel port that run
> >>> LinuxCNC on the Beagle.   Search for MachineKit.
> >>>
> >>> John
> >>>
>  -Original Message-
>  From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
>  Sent: March-18-16 12:27 PM
>  To: Enhanced Machine Controller (EMC)
>  Subject: Re: [Emc-users] Stepper, ideal pulses without feedback
> 
> 
>  Nice box and standard port is always good, I should think about it.
> >>> Steppers
>  are for an xyz engraver so it is essentially a mini CNC machine without
> >>> tool
>  changer.
> 
> 
> 
>  On Fri, 18 Mar 2016 12:00:55 -0700
>  "John Dammeyer"  wrote:
> 
> > You are welcome to look at my Electronic Lead Screw Code.  Follow the
>  link
> > to the code.  It's written for a PIC in C.
> > John
> >
> >
> > "ELS! Nothing else works as well for your Lathe"
> > Automation Artisans Inc.
> > http://www.autoartisans.com/ELS/
> > Ph. 1 250 544 4950
> >
> >
> >
> >
> >> -Original Message-
> >> From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
> >> Sent: March-18-16 11:46 AM
> >> To: emc-users@lists.sourceforge.net
> >> Subject: [Emc-users] Stepper, ideal pulses without feedback
> >>
> >>
> >> I am planning to use a micro controller for stepper step pulse
> >>> generation.
> > I
> >> have considered to use an inverter card but special purpose stepper
> > circuits
> >> are cheap so I use one of these instead. It should be possible to
> >>> feed
> > timer
> >> values then toggle should happen via DMA timer output compare values.
> >>
> >> Can anyone suggest how an ideal step generation curve should look?
> >> Constant acceleration up to top speed? Constant deceleration from top
> >> speed to zero? Or just stop generating pulses?
> >>
> >> Regards Nicklas Karlsson
> >>
> >>
> >
> >>>
> >>> 
> > --
> >> Transform Data into Opportunity.
> >> Accelerate data analysis in your applications with
> >> Intel Data Analytics Acceleration Library.
> >> Click to learn more.
> >> http://pubads.g.doubleclick.net/gampad/clk?id=278785231=/4140
> >> ___
> >> Emc-users mailing list
> >> Emc-users@lists.sourceforge.net
> >> https://lists.sourceforge.net/lists/listinfo/emc-users
> >
> >
> >
> >>>
> >>> 
> >>> --
> > Transform Data into Opportunity.
> > Accelerate data analysis in your applications with
> > Intel Data Analytics Acceleration Library.
> > Click to learn more.
> > http://pubads.g.doubleclick.net/gampad/clk?id=278785231=/4140
> > ___
> > Emc-users mailing list
> > 

Re: [Emc-users] Stepper, ideal pulses without feedback

[Nicklas Karlsson]

It could be a good option so I do not need to have a large computer for a small 
machine. As is know it is more a question about how to ideally 
increases/decrease step rate for a stepper motor?



On Fri, 18 Mar 2016 16:05:31 -0400
John Alexander Stewart  wrote:

> Just FYI - about a year ago or so I purchased from Jeff @xylotex a BBBlack
> and DB-25 cape - ran my Unimat SL CNC'd lathe just fine (feeding a spare
> Gecko G540, 2 axes of which were unused)
> 
> BBBoard from Xylotex came with LinuxCNC Machinekit on a little SDCard. An
> out of the box solution.
> 
> 
> 
> On Fri, Mar 18, 2016 at 3:50 PM, John Dammeyer 
> wrote:
> 
> > You might look at the Replicape and a BeagleBone Black.   There are several
> > other capes including one with a standard DB-25 parallel port that run
> > LinuxCNC on the Beagle.   Search for MachineKit.
> >
> > John
> >
> > > -Original Message-
> > > From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
> > > Sent: March-18-16 12:27 PM
> > > To: Enhanced Machine Controller (EMC)
> > > Subject: Re: [Emc-users] Stepper, ideal pulses without feedback
> > >
> > >
> > > Nice box and standard port is always good, I should think about it.
> > Steppers
> > > are for an xyz engraver so it is essentially a mini CNC machine without
> > tool
> > > changer.
> > >
> > >
> > >
> > > On Fri, 18 Mar 2016 12:00:55 -0700
> > > "John Dammeyer"  wrote:
> > >
> > > > You are welcome to look at my Electronic Lead Screw Code.  Follow the
> > > link
> > > > to the code.  It's written for a PIC in C.
> > > > John
> > > >
> > > >
> > > > "ELS! Nothing else works as well for your Lathe"
> > > > Automation Artisans Inc.
> > > > http://www.autoartisans.com/ELS/
> > > > Ph. 1 250 544 4950
> > > >
> > > >
> > > >
> > > >
> > > > > -Original Message-
> > > > > From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
> > > > > Sent: March-18-16 11:46 AM
> > > > > To: emc-users@lists.sourceforge.net
> > > > > Subject: [Emc-users] Stepper, ideal pulses without feedback
> > > > >
> > > > >
> > > > > I am planning to use a micro controller for stepper step pulse
> > generation.
> > > > I
> > > > > have considered to use an inverter card but special purpose stepper
> > > > circuits
> > > > > are cheap so I use one of these instead. It should be possible to
> > feed
> > > > timer
> > > > > values then toggle should happen via DMA timer output compare values.
> > > > >
> > > > > Can anyone suggest how an ideal step generation curve should look?
> > > > > Constant acceleration up to top speed? Constant deceleration from top
> > > > > speed to zero? Or just stop generating pulses?
> > > > >
> > > > > Regards Nicklas Karlsson
> > > > >
> > > > >
> > > >
> >
> > 
> > > > --
> > > > > Transform Data into Opportunity.
> > > > > Accelerate data analysis in your applications with
> > > > > Intel Data Analytics Acceleration Library.
> > > > > Click to learn more.
> > > > > http://pubads.g.doubleclick.net/gampad/clk?id=278785231=/4140
> > > > > ___
> > > > > Emc-users mailing list
> > > > > Emc-users@lists.sourceforge.net
> > > > > https://lists.sourceforge.net/lists/listinfo/emc-users
> > > >
> > > >
> > > >
> >
> > 
> > --
> > > > Transform Data into Opportunity.
> > > > Accelerate data analysis in your applications with
> > > > Intel Data Analytics Acceleration Library.
> > > > Click to learn more.
> > > > http://pubads.g.doubleclick.net/gampad/clk?id=278785231=/4140
> > > > ___
> > > > Emc-users mailing list
> > > > Emc-users@lists.sourceforge.net
> > > > https://lists.sourceforge.net/lists/listinfo/emc-users
> > >
> > >
> >
> > 
> > --
> > > Transform Data into Opportunity.
> > > Accelerate data analysis in your applications with
> > > Intel Data Analytics Acceleration Library.
> > > Click to learn more.
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> >
> >
> >
> > --
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> >
> 

Re: [Emc-users] Linuxcnc on arm

[W. Martinjak]

Wow, 25% more expensive.
:/

http://www.shop.cncmonster.de/LinuxCNC/FPGA-Karten/USB/Parallelport/7I90HD-Parallel-SPI-Anything-I-O-card::393.html?MODsid=ab1fd9c2053920f289f27a2a6c15f815


Do you know some cheaper offers on this side of the pond?


On 2016-03-16 17:33, andy pugh wrote:
> On 16 March 2016 at 16:20, W. Martinjak  wrote:
>>> http://store.mesanet.com/index.php?route=product/product=83_85_id=291
>> Can you point me to the spec of the spi protocoll of this card?
>> Or the source?
> The spec is in the manual:
> http://www.mesanet.com/pdf/parallel/7i90hdman.pdf
>
> The source is:
> http://git.linuxcnc.org/gitweb?p=hostmot2-firmware.git;a=tree;h=756a26b2fb7df3550b08f8568c80b728818b9a8b;hb=756a26b2fb7df3550b08f8568c80b728818b9a8b
>
> But you shouldn't need all of that, as the driver exists: (But is only
> tested on Odroid as far as I am aware)
> http://git.linuxcnc.org/gitweb?p=linuxcnc.git;a=blob;f=src/hal/drivers/mesa-hostmot2/hm2_spi.c;h=adf2327d35e54c0877e0bdbda8600611febe5313;hb=HEAD
>

-- 
"In der Wissenschaft siegt nie eine neue Theorie,
nur ihre Gegner sterben nach und nach"

Max Planck


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Re: [Emc-users] Linuxcnc on arm

[John Dammeyer]

But see here's where I'm confused.  If Linux already provides priorities of
tasks:
http://www.thegeekstuff.com/2013/08/nice-renice-command-examples/
then the LinuxCNC as a task can run higher than anything else.
If the motion/encoder control is offloaded to a device driver, which should
have even higher priority then where does the real time kernel of the
LinuxCNC fit in?
John Dammeyer

> -Original Message-
> From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
> Sent: March-16-16 9:42 AM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Linuxcnc on arm
> 
> 
> > Real time is not one of the main concerns of the kernel devs. The kernel
> > has graphics drivers that interfere with real time as well as X.
> 
> Probably right no one are interested enough. Good real time performance
> require proper priority of everything handled from interrupts, I also read
> system management interrupts are not possible to get rid of. Knowlegde
> about which real time tasks exist within kernel like serial receive
buffers
> which must be handled before filled up next time or accept lose data is
> probably another issue I never even heard anyone mention.
> 
> 
> Nicklas Karlsson
> 
>

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Re: [Emc-users] Linuxcnc on arm

[W. Martinjak]

On 2016-03-16 17:33, andy pugh wrote:
> On 16 March 2016 at 16:20, W. Martinjak  wrote:
>>> http://store.mesanet.com/index.php?route=product/product=83_85_id=291
>> Can you point me to the spec of the spi protocoll of this card?
>> Or the source?
> The spec is in the manual:
> http://www.mesanet.com/pdf/parallel/7i90hdman.pdf
>
> The source is:
> http://git.linuxcnc.org/gitweb?p=hostmot2-firmware.git;a=tree;h=756a26b2fb7df3550b08f8568c80b728818b9a8b;hb=756a26b2fb7df3550b08f8568c80b728818b9a8b
>
> But you shouldn't need all of that, as the driver exists: (But is only
> tested on Odroid as far as I am aware)
> http://git.linuxcnc.org/gitweb?p=linuxcnc.git;a=blob;f=src/hal/drivers/mesa-hostmot2/hm2_spi.c;h=adf2327d35e54c0877e0bdbda8600611febe5313;hb=HEAD
>
Thanks!
Will dig into ...

-- 
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nur ihre Gegner sterben nach und nach"

Max Planck


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Re: [Emc-users] Linuxcnc on arm

[W. Martinjak]

On 2016-03-16 17:50, John Dammeyer wrote:
>> -Original Message-
>> From: Peter C. Wallace [mailto:p...@mesanet.com]
>>> The ARMs and current crop of PCs are orders of magnitude faster and more
>>> powerful so why is it that the real time part of Linux isn't the defacto
>>> standard for Linux.  If it were wouldn't the latest LinuxCNC run on just
>>> about anything?
>>>
>>> Seems a simple question.  Is there a simple answer?
>>>
>>> John Dammeyer
>>>
>>
>> Preempt-RT will be mainlined into stock linux fairly soon now so its just
>> becomes a kernel config option but I doubt real time kernels will ever be
>> standard for common desktop distributions as they typically have
>> lower performance (excluding latency)  than non RT kernels
>>
> Lower performance?  That seems like an urban legend rather than fact.  Or to
> be more precise, when a bench mark is run on the Preempt-RT it runs slower
> than on the current standard system.And given the speed of processors
> and that memory, disk and display are the limiting factors how is that even
> valid for CNC systems?  Even on desktops.  Is the Linux world so focused on
> video games that require optimum graphics performance.  
>
> The push (and market) in both the windows CNC world and clearly in the
> LinuxCNC is for external hardware to do the physical real time part for
> stepping and encoders especially for new hardware.  Like the MACH3 world for
> people happily running LinuxCNC turning out parts are treating their
> equipment like a tool.  If the tool isn't broken and does the job most won't
> replace it.
>
> In either case that turns the main box part into something that is nothing
> but a trajectory planner and a graphical display interface.  All it has to
> do is provide the motion information to the control part in a timely
> fashion.  
>
> John Dammeyer
>

The problem is different.
RT means looking around and fulfill all tasks in a defined timeslot.
Performance means in most cases move data as fast as you can.
And in some cases it's mutually exclusive.


>
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[Emc-users] Q re these Chinese 3 phase motors.

[Gene Heskett]

Greetings;

This one is a 1.5 horse, 8 amps nameplate rating, air cooled which at low 
speed isn't goping to work at all well anyway, and at 20 Hz drive I am 
quite dissapointed in its torque, 3 or 4 oz/in when the torque boost is 
disabled.  I can stop and hold it between thumb and forefinger quite 
easily.  Turn the torque boost, range 0-4,  up to 0.5, and the apply 
frequency to 50Hz, about doubles the torque but that would be of limited 
usefullness at a 20% duty cycle max is it heats badly, hitting 130F at 
the front bearing plate in about 7 or 8 minutes just laying on the table 
spinning.  So I think its not going to be terribly usefull for g33.1 
tapping unless I add another 10/1 range between the motor and the 
backgear input the current motor drives. Reversing times are well 
subscond at 200Hz drive, so the added gear would seem to make up the 
missing torque.

I've attempted to gain access to removing the collet but have failed as 
it appears to have a spanner hole equipt ring that may be setting a 
bearing preload, so I am hesitant to put a wrench on the collet flats 
and try to loosen it with a set of tru-arc pliers.

Making a short stub shaft to put the existing drive gear from the OEM 
motor on the stub and chucking up the 1/2" sticking out seems like a 
bearing life shortener because of the amount of unsupported shaft 
between the bearings and the gear.  But that looks like the only choice 
if the collet cannot be easily removed.  That of course will need mount 
extensions to make room for the gear train.  All thats do-able of course 
once a suitable set of gears are in hand.  Boston Gear to the rescue I 
suspect.

The front, also black coated ring doesn't seem to meet the piece its 
screwed to with some short 4mm screws, which when I inspected it first, 
was pulled up a bit lopsided with two screws quite tight and the third 
one quite loose leaving a noticeably uneven gap between the parts.  That 
spanner hole equiped ring on the rear of the collet prevents its 
removal, as if the hole in that ring is smaller than the spanner hole 
equiped nut. So it looks as if the spanner holed ring may be the first 
to come off, then this stationary part behind it next, but not knowing 
whats bearing preload, I didn't go any farther.

Has anyone done that collet removal from one of these motors? And can 
guide me on the procedure?  I'd druther not make a $180 pile of junk out 
of it.

Thanks.

Cheers, Gene Heskett
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Re: [Emc-users] Linuxcnc on arm

[Nicklas Karlsson]

On Wed, 16 Mar 2016 13:22:48 +0100
Philipp Burch  wrote:

> Hi Erik,
> 
> as far as I know, MachineKit is a fork of LinuxCNC designed to run on
> ARM platforms:
> http://www.machinekit.io/
> 
> Bye,
> Philipp
> 
> On 16.03.2016 13:17, Erik Friesen wrote:
> > I have been doing some work with an i.mx6 of late, and wonder why the quad
> > couldn't do linuxcnc?  It seems there is some obscure reason I read
> > somewhere.
> > 
> > Older Haas machines use the 68040? 40mhz clunker.
> > 
> > This got me thinking, anyway http://nxgencnc.com/
> > 
> > But I ended up buying a 1996 haas.  Going back to rs232 sort of hurts after
> > networked linuxcnc.

Do not be confused:
  1. Some of the higher end ARM run Linux and it is possible to run Linuxcnc on 
them.
  2. ARM Micro controllers with peripherals suitable for motor control are also 
available.

I checked ARM on ST home page. The cheap lower end Micro controllers have 
peripherals suitable for control of inverter switches for motor control but not 
the higher end. The high end ARM is Multi core and have a lot of CPU power. The 
lower end have an interrupt controller which allow nested interrupts with 
priority, rate monotonic scheduling could be done in hardware with this micro 
controller but I am not sure this interrupt controller is available on the high 
end ARM.

In short the high end ARM is suitable to build something similar to an ordinary 
desktop computer while the cheap are suitable to connect to other hardware 
like: analog input signals, PWM, ...


Nicklas Karlsson


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Re: [Emc-users] Linuxcnc on arm

[andy pugh]

On 16 March 2016 at 16:20, W. Martinjak  wrote:
>
>> http://store.mesanet.com/index.php?route=product/product=83_85_id=291

> Can you point me to the spec of the spi protocoll of this card?
> Or the source?

The spec is in the manual:
http://www.mesanet.com/pdf/parallel/7i90hdman.pdf

The source is:
http://git.linuxcnc.org/gitweb?p=hostmot2-firmware.git;a=tree;h=756a26b2fb7df3550b08f8568c80b728818b9a8b;hb=756a26b2fb7df3550b08f8568c80b728818b9a8b

But you shouldn't need all of that, as the driver exists: (But is only
tested on Odroid as far as I am aware)
http://git.linuxcnc.org/gitweb?p=linuxcnc.git;a=blob;f=src/hal/drivers/mesa-hostmot2/hm2_spi.c;h=adf2327d35e54c0877e0bdbda8600611febe5313;hb=HEAD

-- 
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Re: [Emc-users] Stepper, ideal pulses without feedback

[John Alexander Stewart]

Just FYI - about a year ago or so I purchased from Jeff @xylotex a BBBlack
and DB-25 cape - ran my Unimat SL CNC'd lathe just fine (feeding a spare
Gecko G540, 2 axes of which were unused)

BBBoard from Xylotex came with LinuxCNC Machinekit on a little SDCard. An
out of the box solution.



On Fri, Mar 18, 2016 at 3:50 PM, John Dammeyer 
wrote:

> You might look at the Replicape and a BeagleBone Black.   There are several
> other capes including one with a standard DB-25 parallel port that run
> LinuxCNC on the Beagle.   Search for MachineKit.
>
> John
>
> > -Original Message-
> > From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
> > Sent: March-18-16 12:27 PM
> > To: Enhanced Machine Controller (EMC)
> > Subject: Re: [Emc-users] Stepper, ideal pulses without feedback
> >
> >
> > Nice box and standard port is always good, I should think about it.
> Steppers
> > are for an xyz engraver so it is essentially a mini CNC machine without
> tool
> > changer.
> >
> >
> >
> > On Fri, 18 Mar 2016 12:00:55 -0700
> > "John Dammeyer"  wrote:
> >
> > > You are welcome to look at my Electronic Lead Screw Code.  Follow the
> > link
> > > to the code.  It's written for a PIC in C.
> > > John
> > >
> > >
> > > "ELS! Nothing else works as well for your Lathe"
> > > Automation Artisans Inc.
> > > http://www.autoartisans.com/ELS/
> > > Ph. 1 250 544 4950
> > >
> > >
> > >
> > >
> > > > -Original Message-
> > > > From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
> > > > Sent: March-18-16 11:46 AM
> > > > To: emc-users@lists.sourceforge.net
> > > > Subject: [Emc-users] Stepper, ideal pulses without feedback
> > > >
> > > >
> > > > I am planning to use a micro controller for stepper step pulse
> generation.
> > > I
> > > > have considered to use an inverter card but special purpose stepper
> > > circuits
> > > > are cheap so I use one of these instead. It should be possible to
> feed
> > > timer
> > > > values then toggle should happen via DMA timer output compare values.
> > > >
> > > > Can anyone suggest how an ideal step generation curve should look?
> > > > Constant acceleration up to top speed? Constant deceleration from top
> > > > speed to zero? Or just stop generating pulses?
> > > >
> > > > Regards Nicklas Karlsson
> > > >
> > > >
> > >
>
> 
> > > --
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> > >
> > >
> > >
>
> 
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> >
> >
>
> 
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>
>
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Re: [Emc-users] Linuxcnc on arm

[W. Martinjak]

On 2016-03-16 17:10, andy pugh wrote:
> SPI works well and in conjunction with an FPGA/CPLD very well.
> That might be an interesting setup with:
> http://store.mesanet.com/index.php?route=product/product=83_85_id=291
>

Yep.
Can you point me to the spec of the spi protocoll of this card?
Or the source?

-- 
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nur ihre Gegner sterben nach und nach"

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[Emc-users] Linuxcnc on arm

[Erik Friesen]

I have been doing some work with an i.mx6 of late, and wonder why the quad
couldn't do linuxcnc?  It seems there is some obscure reason I read
somewhere.

Older Haas machines use the 68040? 40mhz clunker.

This got me thinking, anyway http://nxgencnc.com/

But I ended up buying a 1996 haas.  Going back to rs232 sort of hurts after
networked linuxcnc.
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Re: [Emc-users] Stepper, ideal pulses without feedback

[Philipp Burch]

On 19.03.2016 20:20, Nicklas Karlsson wrote:
>> Hi Gene!
>>
>> On 19.03.2016 19:24, Gene Heskett wrote:
>>> [...]
>>>
>>> In 1978 I needed to generate an academy countdown leader, 9.9 to 1.9 
>>> seconds until 1st video, on an RCA 1802 processor, which has built in 
>>> dma.  This thing ran at the smoking clock speed of 1.79 Mhz, but a full 
>>> processor cycle was 8 clocks. Said another way its speed was 223,750 
>>> instructions per second.  And I was able to do it on 6 DMA cycles per 
>>> vertical field, using previously composed data, generating characters 
>>> big enough they could be read on a 5" monitor from 20' away by operators 
>>> with reasonably good eyesight.
>>>
>>> It worked without a hitch even at that slow a machine cycle because any 
>>> time a DMARQ went down, the next machine cycle serviced it.  With 
>>> more "modern" cpu's, that is not always the case. Some treat dma as 
>>> needing a full context dump to the stack first.  Both RCA and TI got it 
>>> right the first time, but TI did have to reload the program counter 
>>> pointer which took a machine cycle. RCA did not as with 16 ea 16 bit 
>>> registers, they just assigned one of them to be the dma access pointer.
>>>
>>> IMO you can smell time wasting stacking of the processor state and its 
>>> recovery when the dma had been serviced 500 yards upwind of a dry lot 
>>> operation on a below zero February morning.  For those of you not raised 
>>> on a farm, I'll just say its legendary and you'll never forget it.
>>>
>>> Modern disclaimer: I have no clue what sort of priority is given DMA by 
>>> todays crop of CPU's.  Sure they've gotten faster, but are they better?
>>
>> It's a bit off-topic, but anyways: DMA controllers in recent
>> microcontrollers can be quite complex beasts, far from a simple
>> incrementing pointer for copy operations. Some use dynamic descriptors
>> in memory, which hold the DMA configuration. One of the config options
>> in each descriptor holds the address of the next descriptor. With this,
>> you can generate "any number" of such descriptors and then start the DMA
>> with the address of the first and it will (optionally looping forever)
>> copy N words from here to there, then M words from foo to bar, followed
>> by K words, etc. without any CPU intervention at all. Usually it is also
>> possible to trigger the DMA using a hardware timer, so you could get
>> away without any interrupt for this transfers at all. But of course the
>> DMA controller has to access the bus as well, so if the CPU is doing
>> some heavy memory access on its own, the DMA may be slowed down quite much.
> 
> Are you sure CPU slow down DMA and not the opposite?

Depends on the priorities, the DMA may be configurable to get higher
priority than the CPU. But I'd suspect the "CPU comes first" approach to
be more common, as the CPU should usually be busy with not so memory
intensive tasks, so performance will increase if it only has to take the
bus every once in a while and continue immediately with its work, while
the DMA is using all the rest of the bandwidth.

Bye,
Philipp



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Re: [Emc-users] Linuxcnc on arm

[bari]

It only sort of does. If a kernel or X dev decides to access hardware 
directly to get his project done he probably will. Unfortunately there 
is no kernel police and no really agreed upon rules that they explicitly 
follow.

On 03/16/2016 12:10 PM, John Dammeyer wrote:
> But see here's where I'm confused.  If Linux already provides priorities of
> tasks:
> http://www.thegeekstuff.com/2013/08/nice-renice-command-examples/
> then the LinuxCNC as a task can run higher than anything else.
> If the motion/encoder control is offloaded to a device driver, which should
> have even higher priority then where does the real time kernel of the
> LinuxCNC fit in?
> John Dammeyer
>
>


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Re: [Emc-users] Linuxcnc on arm

[Nicklas Karlsson]

> But see here's where I'm confused.  If Linux already provides priorities of
> tasks:
> http://www.thegeekstuff.com/2013/08/nice-renice-command-examples/
> then the LinuxCNC as a task can run higher than anything else.
> If the motion/encoder control is offloaded to a device driver, which should
> have even higher priority then where does the real time kernel of the
> LinuxCNC fit in?

For rate monotonic or earliest dead line first scheduling the priority for the 
linuxcnc kernel is assigned according to often it is executed. Even though 
proof of why these schedulings schemes are optimal under som conditions are 
hard assignment of priority is rather simple => assign according to periodicity.

https://en.wikipedia.org/wiki/Rate-monotonic_scheduling
https://en.wikipedia.org/wiki/Earliest_deadline_first_scheduling

Nicklas Karlsson

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Re: [Emc-users] Linuxcnc on arm

[Chris Albertson]

On Sat, Mar 19, 2016 at 12:08 PM, Nicklas Karlsson <
nicklas.karlsso...@gmail.com> wrote:

> On Sat, 19 Mar 2016 13:50:22 -0400
> Gene Heskett  wrote:
>
>
> I am thinking about split in two with real time threads on micro
> controller and the computer for the user interface. It would also be a
> flexible solution then it come to choice of user interface but require
> extra hardware.
>

If I were designing this in the current century (the 21st) I'd divide the
functions roughly in to three (not two) and place them as follows
1) "Hard" real time functions, on a small micro processor not running any
OS.  Maybe something like an ARM  I'd like size the uP so that it could
handle four axis and use multiple uP if more axis were needed
2) The user interface _managment_ and higher level non-real time functions
on a generic "Posix" platform (written in a portable high level language)
 This could be a PC, Mac, Linux/86, LinuxARM)
3) Rendering of the GUI, that is driving the actual screen and
mouse/keyboard.  This would be web-abased and like targeted to a mobile
device like a cheep $100 Android but of course could run on the same
machine as #2 above.

Another words just as you said except I'd drive the screen with some kind
of network protocol (like HTML or whatever) that would be wireless if the
user  prefers that.

One of the more modern architectures I like is ROS (Robot Operating System)
and it can do something like LinuxCNC like for example drive a pick and
place machine or an robot that welds auto bodies on a factory floor.  ROS
is to comp-lex for most CNC machines but it's architecture is good.  It
uses a very large number of processes that communicate via message passing
(publisher/subscribber model) and each processor can run on a separate
computer if you like.  Some real-time, some not.  This allows me to do
things like swap in a simulated sensor for the real on without a even a
restart just be redirecting message routing.  And of course message logging
(and later playback) is a great debugging tool.

One need not go as far as ROS but I'd decouple into three parts (1) RT
stuff, (2) the "guts", and (3) the physical display and user input device




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[Emc-users] Spam

[Gene Heskett]

Greetings all;

I use mailfilter in front of fetchmail, which looks at the incoming email 
while its still on the server & before fetchmail gets to see it, and I 
am finding a huge advantage in all the new .tld's they have issued, as 
its possible to nuke a whole category of spam in just two lines of 
filter.  I'd guess I've cut my spam input by 50% over the last week by 
filtering on the new tld's. I wonder how long it will take the spammers 
to figure that out and demand .com tld's again...

Cheers, Gene Heskett
-- 
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Re: [Emc-users] Linuxcnc on arm

[Nicklas Karlsson]

> So how is that different from a non pre-emptive RTOS kernel?
> 
> My understanding, and it's very superficial, is that the real time component
> of linux puts a scheduler in front of the basic LINUX kernel.  So now the
> micro-stepping or DC-Servo/encoder support can get predictable low latency
> response to events.
> 
> Building that into the kernel so that an application like LinuxCNC can
> acquire the resources to get the same level of access above other hardware
> seems obvious.  For a non LinuxCNC system perhaps the video or network or
> serial port driver will want higher priority than default.  That's a system
> configuration issue.  Not whether the scheduling by the kernel is hard real
> time or soft multi-threaded.

Real time scheduling would probably make sense for all serial receive buffers, 
there is a natural dead line then buffer get full. Or how should execution time 
be assigned to processes otherwise?

> 
> John Dammeyer
> 
> 
> 
> > From: bari [mailto:bari00...@gmail.com]
> > It only sort of does. If a kernel or X dev decides to access hardware
> > directly to get his project done he probably will. Unfortunately there
> > is no kernel police and no really agreed upon rules that they explicitly
> > follow.
> > 
> > On 03/16/2016 12:10 PM, John Dammeyer wrote:
> > > But see here's where I'm confused.  If Linux already provides priorities
> of
> > > tasks:
> > > http://www.thegeekstuff.com/2013/08/nice-renice-command-examples/
> > > then the LinuxCNC as a task can run higher than anything else.
> > > If the motion/encoder control is offloaded to a device driver, which
> > should
> > > have even higher priority then where does the real time kernel of the
> > > LinuxCNC fit in?
> > > John Dammeyer
> > >
> > >
> > 
> > 
> >
> 
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Re: [Emc-users] Stepper, ideal pulses without feedback

[Nicklas Karlsson]

On Sat, 19 Mar 2016 14:24:23 -0400
Gene Heskett  wrote:

> On Saturday 19 March 2016 13:23:27 Nicklas Karlsson wrote:
> 
> > On Sat, 19 Mar 2016 09:52:55 -0700
> >
> > Chris Albertson  wrote:
> > > On Fri, Mar 18, 2016 at 11:46 AM, Nicklas Karlsson <
> > >
> > > nicklas.karlsso...@gmail.com> wrote:
> > > > I am planning to use a micro controller for stepper step pulse
> > > > generation. I have considered to use an inverter card but special
> > > > purpose stepper circuits are cheap so I use one of these instead.
> > > > It should be possible to feed timer values then toggle should
> > > > happen via DMA timer output compare values.
> 
> DMA, for those cpu's that have it built in, can be a VERY useful tool.  
> But since LCNC doesn't seem to use it, I have to assume the worst case 
> scenario exists in modern cpu's...

DMA is not inside Linuxcnc, it is on micro controller I already have on desktop 
with communication to linuxcnc. At each toggle it will transfer at which 
counter value next toggle will happen from a buffer. Another option is to use 
several timers. Timers produce square pulses as perfect as the oscillator 
running while software may have jitter.


Nicklas Karlsson

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Re: [Emc-users] Stepper, ideal pulses without feedback

[Gene Heskett]

On Saturday 19 March 2016 14:40:42 Philipp Burch wrote:

> Hi Gene!
>
> On 19.03.2016 19:24, Gene Heskett wrote:
> > [...]
> >
> > In 1978 I needed to generate an academy countdown leader, 9.9 to 1.9
> > seconds until 1st video, on an RCA 1802 processor, which has built
> > in dma.  This thing ran at the smoking clock speed of 1.79 Mhz, but
> > a full processor cycle was 8 clocks. Said another way its speed was
> > 223,750 instructions per second.  And I was able to do it on 6 DMA
> > cycles per vertical field, using previously composed data,
> > generating characters big enough they could be read on a 5" monitor
> > from 20' away by operators with reasonably good eyesight.
> >
> > It worked without a hitch even at that slow a machine cycle because
> > any time a DMARQ went down, the next machine cycle serviced it. 
> > With more "modern" cpu's, that is not always the case. Some treat
> > dma as needing a full context dump to the stack first.  Both RCA and
> > TI got it right the first time, but TI did have to reload the
> > program counter pointer which took a machine cycle. RCA did not as
> > with 16 ea 16 bit registers, they just assigned one of them to be
> > the dma access pointer.
> >
> > IMO you can smell time wasting stacking of the processor state and
> > its recovery when the dma had been serviced 500 yards upwind of a
> > dry lot operation on a below zero February morning.  For those of
> > you not raised on a farm, I'll just say its legendary and you'll
> > never forget it.
> >
> > Modern disclaimer: I have no clue what sort of priority is given DMA
> > by todays crop of CPU's.  Sure they've gotten faster, but are they
> > better?
>
> It's a bit off-topic, but anyways: DMA controllers in recent
> microcontrollers can be quite complex beasts, far from a simple
> incrementing pointer for copy operations. Some use dynamic descriptors
> in memory, which hold the DMA configuration. One of the config options
> in each descriptor holds the address of the next descriptor. With
> this, you can generate "any number" of such descriptors and then start
> the DMA with the address of the first and it will (optionally looping
> forever) copy N words from here to there, then M words from foo to
> bar, followed by K words, etc. without any CPU intervention at all.
> Usually it is also possible to trigger the DMA using a hardware timer,
> so you could get away without any interrupt for this transfers at all.
> But of course the DMA controller has to access the bus as well, so if
> the CPU is doing some heavy memory access on its own, the DMA may be
> slowed down quite much.
>
> Oh, and there may easily exist multiple DMA controllers in a single
> microcontroller which can be running at the same time. Each of the
> controllers may then also contain dozens of streams. So, yes, I think
> that DMA is given quite some priority in todays microcontrollers.
>
> Cheers,
> Philipp

The RCA version simply transfered bytes in ascending order from memory as 
the dma pointer register was incremented per byte, until DMARQ went back 
high, telling the cpu that this service request ahd been fullfilled.  

Should a logic fault have ocurred that prevented it from going back high 
have occurred, it would have sat there copying memory to that i/o port 
address at nominally 250kb a second till the rapture as the register 
would have looped.  It was up to the programmer and the hardware builder 
to make sure that didn't happen, but since I was a committee of one, 
that was easy to enforce. :)  Nobody else had a clue what the heck I was 
doing, and perhaps didn't even understand why I was doing it.  Shrug...

What I was doing was saving a dub cycle and its quality loss in the aired 
product, and divorcing their quite varigated reaction times from the 
products timing, which made a huge diff in the video quality aired, and 
in the timing consistency.  Nielson book points +2 in the next book. I 
don't have to tell you how important those 2 points were to the sales 
dept. Depending on how its handled, and the market size, $200 in market 
205 to 2+ million a month difference in market #1.  The stations I have 
been affilated with were in the 180 to 160 range.

Cheers, Gene Heskett
-- 
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Re: [Emc-users] Linuxcnc on arm

[Nicklas Karlsson]

On Sat, 19 Mar 2016 13:50:22 -0400
Gene Heskett  wrote:

> On Saturday 19 March 2016 13:08:43 bari wrote:
> 
> > All of memleak's work on RTAI the past few years (which is now RTAI 5
> > without a single credit) was done on AMD hardware made in the past 7
> > years.
> 
> No credits?  'Scuse me but thats not excusable, PM needs to understand 
> TANSTAAFL.
> >
> > Every bit of AMD silicon we touched ran under 25uS on the latency
> > test. Just for fun we had a few tweaked <4uS max jitter.
> 
> This is not an rtai kernel, but 3.16.0-0.bpo.4-amd64.

I am pretty sure I read about some disagreement between RTAI and preemt RT. I 
tried RTAI but had problem with Ethernet, since did not have enough time to 
look at the driver myself I used Premt RT.

I am thinking about split in two with real time threads on micro controller and 
the computer for the user interface. It would also be a flexible solution then 
it come to choice of user interface but require extra hardware.

> 
> latencytest is running here right now, and while the 25 u-s loop last 
> interval displayed is consistently in the 600ns area, the Max Jitter is 
> horrible at 10050977, and Max Interval of 10075977 which is reason 
> enough I'd never in my right mind ever attempt to drive machinery with 
> it without a 5i25 or better card doing the stepper generation, even then 
> 100 milliseconds of lag would trigger the cards WDT,  and quite 
> justifiably so.
> 
> > IME can't be turned off since for security reasons. Security from you.
> 
> Gee, thanks intel.  I love you too...
> 
> > It would be interesting to monitor it on wireshark to see what
> > triggers it to phone home or when it's controlled by hackers. Maybe it
> > kicks in when you trigger interest by using certain words or visit
> > certain websites.
> >
> > On 03/19/2016 11:55 AM, Gene Heskett wrote:
> > > And no way to turn it off?  Makes me glad this machine is an old old
> > > quad core phenom. I haven't seen a thing I couldn't ID in wiresharks
> > > output.
> > >
> > > But 3 of the other machines here, those running real machinery, are
> > > intel, 2-3 yo atoms, or 5-6 yo in a Dell Compact.  AMD stuff cannot
> > > do real time since about K6, which was tolerable, ran one for quite
> > > a spell till I replaced it with the atom stuff, reducing my power
> > > bill.
> > >
> > > I would assume, if they are "calling home" that I could see the
> > > traffic with wireshark or tcpdump?  Hard to see in all the other
> > > traffic as I maintain an sshfs share, and an ssh login session to
> > > them all from here. So its pretty noisy in terms of net traffic here
> > > at the Heskett Cottage.
> >
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> 
> Cheers, Gene Heskett
> -- 
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>  soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> Genes Web page 
> 
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Re: [Emc-users] Linuxcnc on arm

[Gene Heskett]

On Wednesday 16 March 2016 12:50:33 John Dammeyer wrote:

> Seems that's a fault of the graphics drivers and their implementation.
>  The whole point of an RTOS is that tasks can run at priorities that
> serve their needs.  How would placing the video at a higher priority
> be any different than an non-real time system that allows the video to
> run to completion.
>
> Is the problem so simple that the RTOS system clock isn't allowed to
> interrupt the video even if it's just long enough to allow the video
> driver to continue to run at an elevated priority?  I can see that
> with older video hardware from the early 90's but surely things are
> different now?
>
> John

A lot of that difference is because the proprietary drivers lock the 
IRQ's out till they are done, which in my last experiments could be as 
long as 200 milliseconds for the nvidia (spit) blob.  Thats wrecked 
parts and stalled steppers any way you care to measure it.  The nouveau 
driver doesn't do that, so RAI works fine.  I can't testify about the 
ati drivers as I blacklisted those cards at least 8 years ago for the 
simple reason that Alex D. lies worse than a politician.
>
> > Real time is not one of the main concerns of the kernel devs. The
> > kernel has graphics drivers that interfere with real time as well as
> > X.
> >
> > >   The ARMs and current crop of PCs are orders of magnitude faster
> > > and
> >
> > more
> >
> > > powerful so why is it that the real time part of Linux isn't the
> > > defacto standard for Linux.  If it were wouldn't the latest
> > > LinuxCNC run on just about anything?
> > >
> > > Seems a simple question.  Is there a simple answer?
> > >
See the other answers too John.  Yes, its a simple question, but there 
is, sadly, chapter and verse enough of why not to write a boring novel 
with.

> > > John Dammeyer
>
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Cheers, Gene Heskett
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Re: [Emc-users] Stepper, ideal pulses without feedback

[Philipp Burch]

Hi Gene!

On 19.03.2016 19:24, Gene Heskett wrote:
> [...]
> 
> In 1978 I needed to generate an academy countdown leader, 9.9 to 1.9 
> seconds until 1st video, on an RCA 1802 processor, which has built in 
> dma.  This thing ran at the smoking clock speed of 1.79 Mhz, but a full 
> processor cycle was 8 clocks. Said another way its speed was 223,750 
> instructions per second.  And I was able to do it on 6 DMA cycles per 
> vertical field, using previously composed data, generating characters 
> big enough they could be read on a 5" monitor from 20' away by operators 
> with reasonably good eyesight.
> 
> It worked without a hitch even at that slow a machine cycle because any 
> time a DMARQ went down, the next machine cycle serviced it.  With 
> more "modern" cpu's, that is not always the case. Some treat dma as 
> needing a full context dump to the stack first.  Both RCA and TI got it 
> right the first time, but TI did have to reload the program counter 
> pointer which took a machine cycle. RCA did not as with 16 ea 16 bit 
> registers, they just assigned one of them to be the dma access pointer.
> 
> IMO you can smell time wasting stacking of the processor state and its 
> recovery when the dma had been serviced 500 yards upwind of a dry lot 
> operation on a below zero February morning.  For those of you not raised 
> on a farm, I'll just say its legendary and you'll never forget it.
> 
> Modern disclaimer: I have no clue what sort of priority is given DMA by 
> todays crop of CPU's.  Sure they've gotten faster, but are they better?

It's a bit off-topic, but anyways: DMA controllers in recent
microcontrollers can be quite complex beasts, far from a simple
incrementing pointer for copy operations. Some use dynamic descriptors
in memory, which hold the DMA configuration. One of the config options
in each descriptor holds the address of the next descriptor. With this,
you can generate "any number" of such descriptors and then start the DMA
with the address of the first and it will (optionally looping forever)
copy N words from here to there, then M words from foo to bar, followed
by K words, etc. without any CPU intervention at all. Usually it is also
possible to trigger the DMA using a hardware timer, so you could get
away without any interrupt for this transfers at all. But of course the
DMA controller has to access the bus as well, so if the CPU is doing
some heavy memory access on its own, the DMA may be slowed down quite much.

Oh, and there may easily exist multiple DMA controllers in a single
microcontroller which can be running at the same time. Each of the
controllers may then also contain dozens of streams. So, yes, I think
that DMA is given quite some priority in todays microcontrollers.

Cheers,
Philipp



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Re: [Emc-users] Stepper, ideal pulses without feedback

[Gene Heskett]

On Saturday 19 March 2016 13:23:27 Nicklas Karlsson wrote:

> On Sat, 19 Mar 2016 09:52:55 -0700
>
> Chris Albertson  wrote:
> > On Fri, Mar 18, 2016 at 11:46 AM, Nicklas Karlsson <
> >
> > nicklas.karlsso...@gmail.com> wrote:
> > > I am planning to use a micro controller for stepper step pulse
> > > generation. I have considered to use an inverter card but special
> > > purpose stepper circuits are cheap so I use one of these instead.
> > > It should be possible to feed timer values then toggle should
> > > happen via DMA timer output compare values.

DMA, for those cpu's that have it built in, can be a VERY useful tool.  
But since LCNC doesn't seem to use it, I have to assume the worst case 
scenario exists in modern cpu's...

In 1978 I needed to generate an academy countdown leader, 9.9 to 1.9 
seconds until 1st video, on an RCA 1802 processor, which has built in 
dma.  This thing ran at the smoking clock speed of 1.79 Mhz, but a full 
processor cycle was 8 clocks. Said another way its speed was 223,750 
instructions per second.  And I was able to do it on 6 DMA cycles per 
vertical field, using previously composed data, generating characters 
big enough they could be read on a 5" monitor from 20' away by operators 
with reasonably good eyesight.

It worked without a hitch even at that slow a machine cycle because any 
time a DMARQ went down, the next machine cycle serviced it.  With 
more "modern" cpu's, that is not always the case. Some treat dma as 
needing a full context dump to the stack first.  Both RCA and TI got it 
right the first time, but TI did have to reload the program counter 
pointer which took a machine cycle. RCA did not as with 16 ea 16 bit 
registers, they just assigned one of them to be the dma access pointer.

IMO you can smell time wasting stacking of the processor state and its 
recovery when the dma had been serviced 500 yards upwind of a dry lot 
operation on a below zero February morning.  For those of you not raised 
on a farm, I'll just say its legendary and you'll never forget it.

Modern disclaimer: I have no clue what sort of priority is given DMA by 
todays crop of CPU's.  Sure they've gotten faster, but are they better?

> > >
> > > Can anyone suggest how an ideal step generation curve should look?
> > > Constant acceleration up to top speed? Constant deceleration from
> > > top speed to zero? Or just stop generating pulses?
> >
> > So you are NOT using LinuxCNC.  You are planning to roll your own?
>
> No i use Linuxcnc and it currently communicate via Ethernet with a
> micro controller so i stick with this solution for now. I discovered
> motion planner in Linuxcnc have maximum speed and maximum acceleration
> so I have to stick with these to avoid following error at high speed.
> I have chosen a micro stepping driver so I guess linuxcnc servo loop
> is to slow for the toggling.
>
> To output a square pulse on micro controller is very little software,
> I think DMA transfer of table value to timer comparator registers will
> work really well, othewise I could use several timer or software.
>
> As is now I use the micro controller for DC motors with encoder. For
> angle measurement I already have encoder and plan to add resolver. For
> motor types I have DC and plan to add BLDC, PMSM and Asyncronous.
> Maybe I also add sensorless. There are some software libraries
> available at least binaries maybe I use these or write my own.
>
> > I've done this a few times.  My purpose for using CNC is robotics
> > and these robots use motors of various type and move not unlike CNC
> > machines.  All of these motors I always control using some
> > microprocessor.  (ARM or AVR)
> >
> > Generally the pulse rate generator is at the lowest "layer" of
> > abstraction in your software and gets requests from some high layers
> > to do things like move at some rate to some location.  Your software
> > has to try to do what it is requested but subject to physical
> > properties of the motor and mechanical system.  You have to program
> > this in.  Likely maximum acceleration is a function of current
> > speed.  Likely the range of position is limited and so on.  Some
> > requests might have speed or acceleration limits embedded in them
> >
> > After this there is one more important thing that really is done my
> > some layer above the pulse generator and that is planning.  Say you
> > are going to make a U-turn (reverse a motor direction) you might
> > need to slow down before.  This is called "planning" and it's always
> > hard and with robots who work in a changing environment maybe not
> > possible.   But if you are interpreting G-Code you can always just
> > read ahead.
> >
> > Ok there is one case where the pulse generator CAN and should do
> > some planning.  If it gets a request to "move to location X"  it
> > should accelerate to maximum speed, move for some time then
> > DECELERATE and stop at "X" using other max
> >
> > There are some cases where the 

Re: [Emc-users] Linuxcnc on arm

[Jeff Epler]

Linuxcnc 2.7 configured for "uspace" realtime builds and runs on x86,
x86_64 and arm.  our master branch even builds on 64-bit arm.

However, it needs to be paired with a preempt-rt kernel (which generally
only gets latency low enough for servo-cycle-only designs with smart
I/O) and each individual board needs individual hardware drivers.
Nobody has contributed these to the linuxcnc project.

Jeff

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Re: [Emc-users] Linuxcnc on arm

[Jerry Scharf]

Here's my take, which may be as old and tired as I am.

The real issues in RT vs. not RT is not one of standard process scheduling.
There are many knobs and hooks that can control that. The real problem is
in the kernel and drivers, where you can and often have to lock out
interrupts. If those are not designed to work correctly and cooperatively,
things stop being RT. When the person writing the graphics card driver is
told to get as much performance as they can, they often stop thinking about
how polite they are to other time critical things. They have almost no
incentive to be careful and lots of incentive to do what makes things go
the fastest.

One issue in particular that becomes difficult is spin locks for
multiprocessor kernels. They have to deal with the memory access system and
adding complexity in these has dramatic system throughput impacts even when
code branches are not executed. I am not a multiprocessor kernel expert but
I have worked with a few. Small differences in how the locking works can
raise and lower system throughput by 10%. Hard to sell adding things to the
generic kernel that slow everyone down and are only useful to a small
percentage of users.

This work was from 20 years ago, but I know of nothing that has changed in
what OS locks need to do that change the impact of this kind of locking.
Improving lock delays is one of the biggest things that OS designers do and
they spend years on it.


jerry


On Wed, Mar 16, 2016 at 12:11 PM, John Dammeyer 
wrote:

> So how is that different from a non pre-emptive RTOS kernel?
>
> My understanding, and it's very superficial, is that the real time
> component
> of linux puts a scheduler in front of the basic LINUX kernel.  So now the
> micro-stepping or DC-Servo/encoder support can get predictable low latency
> response to events.
>
> Building that into the kernel so that an application like LinuxCNC can
> acquire the resources to get the same level of access above other hardware
> seems obvious.  For a non LinuxCNC system perhaps the video or network or
> serial port driver will want higher priority than default.  That's a system
> configuration issue.  Not whether the scheduling by the kernel is hard real
> time or soft multi-threaded.
>
> John Dammeyer
>
>
>
> > From: bari [mailto:bari00...@gmail.com]
> > It only sort of does. If a kernel or X dev decides to access hardware
> > directly to get his project done he probably will. Unfortunately there
> > is no kernel police and no really agreed upon rules that they explicitly
> > follow.
> >
> > On 03/16/2016 12:10 PM, John Dammeyer wrote:
> > > But see here's where I'm confused.  If Linux already provides
> priorities
> of
> > > tasks:
> > > http://www.thegeekstuff.com/2013/08/nice-renice-command-examples/
> > > then the LinuxCNC as a task can run higher than anything else.
> > > If the motion/encoder control is offloaded to a device driver, which
> > should
> > > have even higher priority then where does the real time kernel of the
> > > LinuxCNC fit in?
> > > John Dammeyer
> > >
> > >
> >
> >
> >
>
> 
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Re: [Emc-users] Linuxcnc on arm

[Erik Friesen]

I am using the embeddedarm ts4900, seems more industrialized than the
beagle/rasberi pi solutions.  Plus, you can get answers on the phone in a
pinch.  The buck tends to stop nowhere with the rasberi solutions.

My first go around was with the RiotBoard, which would randomly refuse to
boot.

On Wed, Mar 16, 2016 at 11:52 AM, W. Martinjak  wrote:

> On 2016-03-16 16:41, andy pugh wrote:
> > On 16 March 2016 at 15:35, Yanjun Luo  wrote:
> >> Hi,
> >> I think Raspberry Pi Module 3 is a good choice, I'll try it when I get a
> >> board soon
> > The problem with the Pi is that the obvious choice for IO, Ethernet,
> > is  connected via the USB bus.
> >
>
> But SPI works well and in conjunction with an FPGA/CPLD very well.
>
> --
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> nur ihre Gegner sterben nach und nach"
>
> Max Planck
>
>
>
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Re: [Emc-users] Linuxcnc on arm

[Gene Heskett]

On Saturday 19 March 2016 13:08:43 bari wrote:

> All of memleak's work on RTAI the past few years (which is now RTAI 5
> without a single credit) was done on AMD hardware made in the past 7
> years.

No credits?  'Scuse me but thats not excusable, PM needs to understand 
TANSTAAFL.
>
> Every bit of AMD silicon we touched ran under 25uS on the latency
> test. Just for fun we had a few tweaked <4uS max jitter.

This is not an rtai kernel, but 3.16.0-0.bpo.4-amd64. 

latencytest is running here right now, and while the 25 u-s loop last 
interval displayed is consistently in the 600ns area, the Max Jitter is 
horrible at 10050977, and Max Interval of 10075977 which is reason 
enough I'd never in my right mind ever attempt to drive machinery with 
it without a 5i25 or better card doing the stepper generation, even then 
100 milliseconds of lag would trigger the cards WDT,  and quite 
justifiably so.

> IME can't be turned off since for security reasons. Security from you.

Gee, thanks intel.  I love you too...

> It would be interesting to monitor it on wireshark to see what
> triggers it to phone home or when it's controlled by hackers. Maybe it
> kicks in when you trigger interest by using certain words or visit
> certain websites.
>
> On 03/19/2016 11:55 AM, Gene Heskett wrote:
> > And no way to turn it off?  Makes me glad this machine is an old old
> > quad core phenom. I haven't seen a thing I couldn't ID in wiresharks
> > output.
> >
> > But 3 of the other machines here, those running real machinery, are
> > intel, 2-3 yo atoms, or 5-6 yo in a Dell Compact.  AMD stuff cannot
> > do real time since about K6, which was tolerable, ran one for quite
> > a spell till I replaced it with the atom stuff, reducing my power
> > bill.
> >
> > I would assume, if they are "calling home" that I could see the
> > traffic with wireshark or tcpdump?  Hard to see in all the other
> > traffic as I maintain an sshfs share, and an ssh login session to
> > them all from here. So its pretty noisy in terms of net traffic here
> > at the Heskett Cottage.
>
> --
> Transform Data into Opportunity.
> Accelerate data analysis in your applications with
> Intel Data Analytics Acceleration Library.
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Cheers, Gene Heskett
-- 
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 soap, ballot, jury, and ammo. Please use in that order."
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Re: [Emc-users] Stepper, ideal pulses without feedback

[Nicklas Karlsson]

I have seen and run machinekit, it is linuxcnc. I have also read about 
BeagleBone. There are plenty of devices suitable to generate the pulses but at 
which rate should pulses generated? Constant acceleration between different 
speeds?


On Fri, 18 Mar 2016 12:50:21 -0700
"John Dammeyer"  wrote:

> You might look at the Replicape and a BeagleBone Black.   There are several
> other capes including one with a standard DB-25 parallel port that run
> LinuxCNC on the Beagle.   Search for MachineKit.
> 
> John
> 
> > -Original Message-
> > From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
> > Sent: March-18-16 12:27 PM
> > To: Enhanced Machine Controller (EMC)
> > Subject: Re: [Emc-users] Stepper, ideal pulses without feedback
> > 
> > 
> > Nice box and standard port is always good, I should think about it.
> Steppers
> > are for an xyz engraver so it is essentially a mini CNC machine without
> tool
> > changer.
> > 
> > 
> > 
> > On Fri, 18 Mar 2016 12:00:55 -0700
> > "John Dammeyer"  wrote:
> > 
> > > You are welcome to look at my Electronic Lead Screw Code.  Follow the
> > link
> > > to the code.  It's written for a PIC in C.
> > > John
> > >
> > >
> > > "ELS! Nothing else works as well for your Lathe"
> > > Automation Artisans Inc.
> > > http://www.autoartisans.com/ELS/
> > > Ph. 1 250 544 4950
> > >
> > >
> > >
> > >
> > > > -Original Message-
> > > > From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
> > > > Sent: March-18-16 11:46 AM
> > > > To: emc-users@lists.sourceforge.net
> > > > Subject: [Emc-users] Stepper, ideal pulses without feedback
> > > >
> > > >
> > > > I am planning to use a micro controller for stepper step pulse
> generation.
> > > I
> > > > have considered to use an inverter card but special purpose stepper
> > > circuits
> > > > are cheap so I use one of these instead. It should be possible to feed
> > > timer
> > > > values then toggle should happen via DMA timer output compare values.
> > > >
> > > > Can anyone suggest how an ideal step generation curve should look?
> > > > Constant acceleration up to top speed? Constant deceleration from top
> > > > speed to zero? Or just stop generating pulses?
> > > >
> > > > Regards Nicklas Karlsson
> > > >
> > > >
> > >
> 
> > > --
> > > > Transform Data into Opportunity.
> > > > Accelerate data analysis in your applications with
> > > > Intel Data Analytics Acceleration Library.
> > > > Click to learn more.
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> > > > ___
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> > > > https://lists.sourceforge.net/lists/listinfo/emc-users
> > >
> > >
> > >
> 
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> > > Click to learn more.
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> > > https://lists.sourceforge.net/lists/listinfo/emc-users
> > 
> >
> 
> --
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> > Accelerate data analysis in your applications with
> > Intel Data Analytics Acceleration Library.
> > Click to learn more.
> > http://pubads.g.doubleclick.net/gampad/clk?id=278785231=/4140
> > ___
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> > https://lists.sourceforge.net/lists/listinfo/emc-users
> 
> 
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Re: [Emc-users] Stepper, ideal pulses without feedback

[Nicklas Karlsson]

On Sat, 19 Mar 2016 09:52:55 -0700
Chris Albertson  wrote:

> On Fri, Mar 18, 2016 at 11:46 AM, Nicklas Karlsson <
> nicklas.karlsso...@gmail.com> wrote:
> 
> > I am planning to use a micro controller for stepper step pulse generation.
> > I have considered to use an inverter card but special purpose stepper
> > circuits are cheap so I use one of these instead. It should be possible to
> > feed timer values then toggle should happen via DMA timer output compare
> > values.
> >
> > Can anyone suggest how an ideal step generation curve should look?
> > Constant acceleration up to top speed? Constant deceleration from top speed
> > to zero? Or just stop generating pulses?
> >
> 
> So you are NOT using LinuxCNC.  You are planning to roll your own?

No i use Linuxcnc and it currently communicate via Ethernet with a micro 
controller so i stick with this solution for now. I discovered motion planner 
in Linuxcnc have maximum speed and maximum acceleration so I have to stick with 
these to avoid following error at high speed. I have chosen a micro stepping 
driver so I guess linuxcnc servo loop is to slow for the toggling.

To output a square pulse on micro controller is very little software, I think 
DMA transfer of table value to timer comparator registers will work really 
well, othewise I could use several timer or software.

As is now I use the micro controller for DC motors with encoder. For angle 
measurement I already have encoder and plan to add resolver. For motor types I 
have DC and plan to add BLDC, PMSM and Asyncronous. Maybe I also add 
sensorless. There are some software libraries available at least binaries maybe 
I use these or write my own.


> 
> I've done this a few times.  My purpose for using CNC is robotics and these
> robots use motors of various type and move not unlike CNC machines.  All of
> these motors I always control using some microprocessor.  (ARM or AVR)
> 
> Generally the pulse rate generator is at the lowest "layer" of abstraction
> in your software and gets requests from some high layers to do things like
> move at some rate to some location.  Your software has to try to do what it
> is requested but subject to physical properties of the motor and mechanical
> system.  You have to program this in.  Likely maximum acceleration is a
> function of current speed.  Likely the range of position is limited and so
> on.  Some requests might have speed or acceleration limits embedded in them
> 
> After this there is one more important thing that really is done my some
> layer above the pulse generator and that is planning.  Say you are going to
> make a U-turn (reverse a motor direction) you might need to slow down
> before.  This is called "planning" and it's always hard and with robots who
> work in a changing environment maybe not possible.   But if you are
> interpreting G-Code you can always just read ahead.
> 
> Ok there is one case where the pulse generator CAN and should do some
> planning.  If it gets a request to "move to location X"  it should
> accelerate to maximum speed, move for some time then DECELERATE and stop at
> "X" using other max
> 
> There are some cases where the pulse generator MUST work with more then one
> motor at the same time.  What if the request is to "move in a circle"  or
> if doing threading on a lathe to move the spindle and leadscrew in
> "lock-step".  In my case I want to move a caterpillar-tread robot along an
> arc of given radios so that it passes through the center of a doorway.
> The limiting factor is the performance of the "outside" tread motor.  In
> general what running multiple motors one of then will hit a performance
> limit first and the others need to have their accelerations limited.
> 
> The easiest thing for you to do is use software that others have written
> and get it to work some how on the platform your choose (An ARM based SBC
> like the beagle bored or "Pi")   For CNC work LinucCNC already does what
> you need and for robotics look up "ROS".  Both of these can run on a
> computer the size of a credit card.
> 
> 
> 
> Now getting to your specific question of wetter to use constant
> acceleration (linearly increasing speed) or some kind of curve.  The above
> should have answered this.  The pulse generator will try for maximum
> performance which is constant acceleration but may run into physical
> limitation of the motor and mechanics where available torque is a function
> of speed and this will cause acceleration if tapper off.   On the other
> hand if the request has an embedded limit you may not het mechanical
> limitations and you can actually do constant acceleration up to the
> commanded speed.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> -- 
> 
> Chris Albertson
> Redondo Beach, California
> --
> Transform Data into Opportunity.
> Accelerate data analysis in your applications with
> Intel Data Analytics Acceleration Library.
> 

Re: [Emc-users] Stepper, ideal pulses without feedback

[Gene Heskett]

On Saturday 19 March 2016 12:52:55 Chris Albertson wrote:

> On Fri, Mar 18, 2016 at 11:46 AM, Nicklas Karlsson <
>
> nicklas.karlsso...@gmail.com> wrote:
> > I am planning to use a micro controller for stepper step pulse
> > generation. I have considered to use an inverter card but special
> > purpose stepper circuits are cheap so I use one of these instead. It
> > should be possible to feed timer values then toggle should happen
> > via DMA timer output compare values.
> >
> > Can anyone suggest how an ideal step generation curve should look?
> > Constant acceleration up to top speed? Constant deceleration from
> > top speed to zero? Or just stop generating pulses?
>
> So you are NOT using LinuxCNC.  You are planning to roll your own?
>
> I've done this a few times.  My purpose for using CNC is robotics and
> these robots use motors of various type and move not unlike CNC
> machines.  All of these motors I always control using some
> microprocessor.  (ARM or AVR)
>
> Generally the pulse rate generator is at the lowest "layer" of
> abstraction in your software and gets requests from some high layers
> to do things like move at some rate to some location.  Your software
> has to try to do what it is requested but subject to physical
> properties of the motor and mechanical system.  You have to program
> this in.  Likely maximum acceleration is a function of current speed. 
> Likely the range of position is limited and so on.  Some requests
> might have speed or acceleration limits embedded in them
>
> After this there is one more important thing that really is done my
> some layer above the pulse generator and that is planning.  Say you
> are going to make a U-turn (reverse a motor direction) you might need
> to slow down before.  This is called "planning" and it's always hard
> and with robots who work in a changing environment maybe not possible.
>   But if you are interpreting G-Code you can always just read ahead.
>
> Ok there is one case where the pulse generator CAN and should do some
> planning.  If it gets a request to "move to location X"  it should
> accelerate to maximum speed, move for some time then DECELERATE and
> stop at "X" using other max
>
> There are some cases where the pulse generator MUST work with more
> then one motor at the same time.  What if the request is to "move in a
> circle"  or if doing threading on a lathe to move the spindle and
> leadscrew in "lock-step".  In my case I want to move a
> caterpillar-tread robot along an arc of given radios so that it passes
> through the center of a doorway. The limiting factor is the
> performance of the "outside" tread motor.  In general what running
> multiple motors one of then will hit a performance limit first and the
> others need to have their accelerations limited.
>
> The easiest thing for you to do is use software that others have
> written and get it to work some how on the platform your choose (An
> ARM based SBC like the beagle bored or "Pi")   For CNC work LinucCNC
> already does what you need and for robotics look up "ROS".  Both of
> these can run on a computer the size of a credit card.
>
>
>
> Now getting to your specific question of wetter to use constant
> acceleration (linearly increasing speed) or some kind of curve.  The
> above should have answered this.  The pulse generator will try for
> maximum performance which is constant acceleration but may run into
> physical limitation of the motor and mechanics where available torque
> is a function of speed and this will cause acceleration if tapper off.

But the stepper generator itself does NOT know when this limit is 
encountered, so the acceleration tapers off alright, to a loss of 
synchronization stop, usually in less than another 90 degrees of 
rotation, determined by its mass and the load pushing it.  AKA a stall.

Lost part, broken tool, what have you mayhem follows.

The only way for the software to know the motor has lost synch, is with 
an encoder on the motor with a resolution equal to or better than the 
microstepping in use.

Unless and until the drivers develop a method to detect that, AND return 
a FAIL signal to our software, we are stuck with that situation.

Servo systems can do this quite well simply by watching the PID.error 
output.

But steppers, which normally have no such feedback path, are crippled in 
that reporting, so you have the stalls and broken tooling and wrecked 
parts that go with pushing a stepper out of its comfort zone.

>   On the other hand if the request has an embedded limit you may not
> het mechanical limitations and you can actually do constant
> acceleration up to the commanded speed.

Which is what we do. But violated accel limits seem easy to detect. Run 
the x table at full speed to the limit which should be 50 thou or so 
away from the hard limit.  This because of the unbalance weight of the 
table hanging out out, adds to the way friction quite a bit if it hasn't 
been oiled in the last 10 minutes.

Then try to move 

Re: [Emc-users] Linuxcnc on arm

[bari]

All of memleak's work on RTAI the past few years (which is now RTAI 5 
without a single credit) was done on AMD hardware made in the past 7 years.

Every bit of AMD silicon we touched ran under 25uS on the latency test. 
Just for fun we had a few tweaked <4uS max jitter.

IME can't be turned off since for security reasons. Security from you.

It would be interesting to monitor it on wireshark to see what triggers 
it to phone home or when it's controlled by hackers. Maybe it kicks in 
when you trigger interest by using certain words or visit certain websites.


On 03/19/2016 11:55 AM, Gene Heskett wrote:
> And no way to turn it off?  Makes me glad this machine is an old old quad
> core phenom. I haven't seen a thing I couldn't ID in wiresharks output.
>
> But 3 of the other machines here, those running real machinery, are
> intel, 2-3 yo atoms, or 5-6 yo in a Dell Compact.  AMD stuff cannot do
> real time since about K6, which was tolerable, ran one for quite a spell
> till I replaced it with the atom stuff, reducing my power bill.
>
> I would assume, if they are "calling home" that I could see the traffic
> with wireshark or tcpdump?  Hard to see in all the other traffic as I
> maintain an sshfs share, and an ssh login session to them all from here.
> So its pretty noisy in terms of net traffic here at the Heskett Cottage.


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Re: [Emc-users] Linuxcnc on arm

[Gene Heskett]

On Saturday 19 March 2016 10:35:07 bari wrote:

> One more thing I forgot to mention that can add to poor real time
> performance on x86 is BIOS/firmware. Intel has forced the use of their
> Intel Management Engine that allows for remote control, phone home,
> backdoor etc and operates completely out of band. So you'd never
> notice it unless you monitor the network activity or the hardware and
> look for unexplained delays.
>
> http://www.slideshare.net/codeblue_jp/igor-skochinsky-enpub
> Has a good write-up and sideshow on how it works.

Interesting link.

And no way to turn it off?  Makes me glad this machine is an old old quad 
core phenom. I haven't seen a thing I couldn't ID in wiresharks output.

But 3 of the other machines here, those running real machinery, are 
intel, 2-3 yo atoms, or 5-6 yo in a Dell Compact.  AMD stuff cannot do 
real time since about K6, which was tolerable, ran one for quite a spell 
till I replaced it with the atom stuff, reducing my power bill.

I would assume, if they are "calling home" that I could see the traffic 
with wireshark or tcpdump?  Hard to see in all the other traffic as I 
maintain an sshfs share, and an ssh login session to them all from here.  
So its pretty noisy in terms of net traffic here at the Heskett Cottage.

> On 03/16/2016 04:12 PM, Jcd wrote:
> > So what makes the real time Linux like machine kit or for a regular
> > PC. If drivers can muck things up.
>
> --
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> Intel Data Analytics Acceleration Library.
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Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Stepper, ideal pulses without feedback

[Chris Albertson]

On Fri, Mar 18, 2016 at 11:46 AM, Nicklas Karlsson <
nicklas.karlsso...@gmail.com> wrote:

> I am planning to use a micro controller for stepper step pulse generation.
> I have considered to use an inverter card but special purpose stepper
> circuits are cheap so I use one of these instead. It should be possible to
> feed timer values then toggle should happen via DMA timer output compare
> values.
>
> Can anyone suggest how an ideal step generation curve should look?
> Constant acceleration up to top speed? Constant deceleration from top speed
> to zero? Or just stop generating pulses?
>

So you are NOT using LinuxCNC.  You are planning to roll your own?

I've done this a few times.  My purpose for using CNC is robotics and these
robots use motors of various type and move not unlike CNC machines.  All of
these motors I always control using some microprocessor.  (ARM or AVR)

Generally the pulse rate generator is at the lowest "layer" of abstraction
in your software and gets requests from some high layers to do things like
move at some rate to some location.  Your software has to try to do what it
is requested but subject to physical properties of the motor and mechanical
system.  You have to program this in.  Likely maximum acceleration is a
function of current speed.  Likely the range of position is limited and so
on.  Some requests might have speed or acceleration limits embedded in them

After this there is one more important thing that really is done my some
layer above the pulse generator and that is planning.  Say you are going to
make a U-turn (reverse a motor direction) you might need to slow down
before.  This is called "planning" and it's always hard and with robots who
work in a changing environment maybe not possible.   But if you are
interpreting G-Code you can always just read ahead.

Ok there is one case where the pulse generator CAN and should do some
planning.  If it gets a request to "move to location X"  it should
accelerate to maximum speed, move for some time then DECELERATE and stop at
"X" using other max

There are some cases where the pulse generator MUST work with more then one
motor at the same time.  What if the request is to "move in a circle"  or
if doing threading on a lathe to move the spindle and leadscrew in
"lock-step".  In my case I want to move a caterpillar-tread robot along an
arc of given radios so that it passes through the center of a doorway.
The limiting factor is the performance of the "outside" tread motor.  In
general what running multiple motors one of then will hit a performance
limit first and the others need to have their accelerations limited.

The easiest thing for you to do is use software that others have written
and get it to work some how on the platform your choose (An ARM based SBC
like the beagle bored or "Pi")   For CNC work LinucCNC already does what
you need and for robotics look up "ROS".  Both of these can run on a
computer the size of a credit card.



Now getting to your specific question of wetter to use constant
acceleration (linearly increasing speed) or some kind of curve.  The above
should have answered this.  The pulse generator will try for maximum
performance which is constant acceleration but may run into physical
limitation of the motor and mechanics where available torque is a function
of speed and this will cause acceleration if tapper off.   On the other
hand if the request has an embedded limit you may not het mechanical
limitations and you can actually do constant acceleration up to the
commanded speed.










-- 

Chris Albertson
Redondo Beach, California
--
Transform Data into Opportunity.
Accelerate data analysis in your applications with
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Re: [Emc-users] Linuxcnc on arm

[W. Martinjak]

Wow,

6 weeks after I asked this question on the devel-list
https://sourceforge.net/p/emc/mailman/message/34817886/
and irc
http://tom-itx.no-ip.biz:81/~tom-itx/irc/logs/%23linuxcnc-devel/2016-02-03.html#10:00:50

there is suddenly an answer.
And without chunk on the user-list.

What I've done wrong?





On 2016-03-16 13:38, Jeff Epler wrote:
> Linuxcnc 2.7 configured for "uspace" realtime builds and runs on x86,
> x86_64 and arm.  our master branch even builds on 64-bit arm.
>
> However, it needs to be paired with a preempt-rt kernel (which generally
> only gets latency low enough for servo-cycle-only designs with smart
> I/O) and each individual board needs individual hardware drivers.
> Nobody has contributed these to the linuxcnc project.
>
> Jeff
>
> --
> Transform Data into Opportunity.
> Accelerate data analysis in your applications with
> Intel Data Analytics Acceleration Library.
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Re: [Emc-users] Stepper, ideal pulses without feedback

[Nicklas Karlsson]

Nice box and standard port is always good, I should think about it. Steppers 
are for an xyz engraver so it is essentially a mini CNC machine without tool 
changer.



On Fri, 18 Mar 2016 12:00:55 -0700
"John Dammeyer"  wrote:

> You are welcome to look at my Electronic Lead Screw Code.  Follow the link
> to the code.  It's written for a PIC in C.
> John
> 
> 
> "ELS! Nothing else works as well for your Lathe"
> Automation Artisans Inc.
> http://www.autoartisans.com/ELS/
> Ph. 1 250 544 4950
> 
> 
> 
> 
> > -Original Message-
> > From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
> > Sent: March-18-16 11:46 AM
> > To: emc-users@lists.sourceforge.net
> > Subject: [Emc-users] Stepper, ideal pulses without feedback
> > 
> > 
> > I am planning to use a micro controller for stepper step pulse generation.
> I
> > have considered to use an inverter card but special purpose stepper
> circuits
> > are cheap so I use one of these instead. It should be possible to feed
> timer
> > values then toggle should happen via DMA timer output compare values.
> > 
> > Can anyone suggest how an ideal step generation curve should look?
> > Constant acceleration up to top speed? Constant deceleration from top
> > speed to zero? Or just stop generating pulses?
> > 
> > Regards Nicklas Karlsson
> > 
> >
> 
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Re: [Emc-users] Linuxcnc on arm

[Stephen Dubovsky]

And there are some that do both 1 *AND* 2.  Look at the Xilinx Zynq for
example.  Dual gigahertz A9 cores w/ a FPGA core (Spartan/Virtex) that IIRC
is larger than the one used for the Mesa 5i25.  Could run a zillion
channels of PWM or even hostmot2.  We were porting some code to it for a
work project that had 16+ PWM channels. We didn't need linux but were still
only using one core to do real time control.

SMD

On Wed, Mar 16, 2016 at 9:54 AM, Nicklas Karlsson <
nicklas.karlsso...@gmail.com> wrote:

> On Wed, 16 Mar 2016 13:22:48 +0100
> Philipp Burch  wrote:
>
> > Hi Erik,
> >
> > as far as I know, MachineKit is a fork of LinuxCNC designed to run on
> > ARM platforms:
> > http://www.machinekit.io/
> >
> > Bye,
> > Philipp
> >
> > On 16.03.2016 13:17, Erik Friesen wrote:
> > > I have been doing some work with an i.mx6 of late, and wonder why the
> quad
> > > couldn't do linuxcnc?  It seems there is some obscure reason I read
> > > somewhere.
> > >
> > > Older Haas machines use the 68040? 40mhz clunker.
> > >
> > > This got me thinking, anyway http://nxgencnc.com/
> > >
> > > But I ended up buying a 1996 haas.  Going back to rs232 sort of hurts
> after
> > > networked linuxcnc.
>
> Do not be confused:
>   1. Some of the higher end ARM run Linux and it is possible to run
> Linuxcnc on them.
>   2. ARM Micro controllers with peripherals suitable for motor control are
> also available.
>
> I checked ARM on ST home page. The cheap lower end Micro controllers have
> peripherals suitable for control of inverter switches for motor control but
> not the higher end. The high end ARM is Multi core and have a lot of CPU
> power. The lower end have an interrupt controller which allow nested
> interrupts with priority, rate monotonic scheduling could be done in
> hardware with this micro controller but I am not sure this interrupt
> controller is available on the high end ARM.
>
> In short the high end ARM is suitable to build something similar to an
> ordinary desktop computer while the cheap are suitable to connect to other
> hardware like: analog input signals, PWM, ...
>
>
> Nicklas Karlsson
>
>
>
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Re: [Emc-users] Linuxcnc on arm

[Jon Elson]

On 03/16/2016 07:22 AM, Philipp Burch wrote:
> Hi Erik,
>
> as far as I know, MachineKit is a fork of LinuxCNC designed to run on
> ARM platforms:
> http://www.machinekit.io/
>
>
Yes, it is basically LinuxCNC as far as the user would see, 
but has a number of extensions underneath.

But, it doesn't support many of the external hardware 
interfaces that are available on the X86 versions.
I think some work is being done to address that.

Jon

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Re: [Emc-users] Linuxcnc on arm

[bari]

One more thing I forgot to mention that can add to poor real time 
performance on x86 is BIOS/firmware. Intel has forced the use of their 
Intel Management Engine that allows for remote control, phone home, 
backdoor etc and operates completely out of band. So you'd never notice 
it unless you monitor the network activity or the hardware and look for 
unexplained delays.

http://www.slideshare.net/codeblue_jp/igor-skochinsky-enpub
Has a good write-up and sideshow on how it works.

On 03/16/2016 04:12 PM, Jcd wrote:
> So what makes the real time Linux like machine kit or for a regular PC. If 
> drivers can muck things up.


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Re: [Emc-users] Linuxcnc on arm

[John Dammeyer]

As I understand it, the MachineKit was forked from an earlier version of
LinuxCNC and LinuxCNC requires a real time kernel to run.

Why is it that the real time kernel hasn't become a basic part of Linux so
that the orphan Linux is the one without the kernel? 

Surely by now we've moved past the 486DX4-100 level of processors.  IC've
written an RTOS for an 8 bit NEC78C10, worked with VRTX RTOS on x86 CPUs and
written software for Motorola MC68070 processors running OS9-68K.  

 The ARMs and current crop of PCs are orders of magnitude faster and more
powerful so why is it that the real time part of Linux isn't the defacto
standard for Linux.  If it were wouldn't the latest LinuxCNC run on just
about anything?

Seems a simple question.  Is there a simple answer?

John Dammeyer




> -Original Message-
> From: Sebastian Kuzminsky [mailto:s...@highlab.com]
> Sent: March-16-16 8:29 AM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Linuxcnc on arm
> 
> 
> On 03/16/2016 08:25 AM, W. Martinjak wrote:
> > It's emty.
> >
> > http://buildbot.linuxcnc.org/dists/wheezy/2.7-rtpreempt/binary-armhf/
> > http://buildbot.linuxcnc.org/dists/wheezy/master-rtpreempt/binary-
> armhf/
> 
> We build and test on arm, but we currently don't produce debian packages.
> 
> LinuxCNC 2.7 and newer work on Wheezy on armhf, you just have to build
> it yourself:
> 
> http://buildbot.linuxcnc.org/buildbot/builders/1405.rip-wheezy-armhf
> 
> 
> --
> Sebastian Kuzminsky
> 
>

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Re: [Emc-users] Linuxcnc on arm

[John Dammeyer]

> -Original Message-
> From: Peter C. Wallace [mailto:p...@mesanet.com]
> >
> > The ARMs and current crop of PCs are orders of magnitude faster and more
> > powerful so why is it that the real time part of Linux isn't the defacto
> > standard for Linux.  If it were wouldn't the latest LinuxCNC run on just
> > about anything?
> >
> > Seems a simple question.  Is there a simple answer?
> >
> > John Dammeyer
> >
> 
> 
> Preempt-RT will be mainlined into stock linux fairly soon now so its just
> becomes a kernel config option but I doubt real time kernels will ever be
> standard for common desktop distributions as they typically have
> lower performance (excluding latency)  than non RT kernels
> 
Lower performance?  That seems like an urban legend rather than fact.  Or to
be more precise, when a bench mark is run on the Preempt-RT it runs slower
than on the current standard system.And given the speed of processors
and that memory, disk and display are the limiting factors how is that even
valid for CNC systems?  Even on desktops.  Is the Linux world so focused on
video games that require optimum graphics performance.  

The push (and market) in both the windows CNC world and clearly in the
LinuxCNC is for external hardware to do the physical real time part for
stepping and encoders especially for new hardware.  Like the MACH3 world for
people happily running LinuxCNC turning out parts are treating their
equipment like a tool.  If the tool isn't broken and does the job most won't
replace it.

In either case that turns the main box part into something that is nothing
but a trajectory planner and a graphical display interface.  All it has to
do is provide the motion information to the control part in a timely
fashion.  

John Dammeyer



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Re: [Emc-users] Linuxcnc on arm

[Nicklas Karlsson]

That's why I think the other direction and put the real time stuff on a micro 
controller, there are no graphic drivers to think about. I think it is the 
motion-command-handler and motion-controller threads.

I expect bandwidth required to communicate with the GUI would be rather low. 
With real time demand removed from the GUI it could be more freely deployed on 
for example a wireless device.


> That's why we'd need the kernel police to enforce the rules, if there 
> were kernel rules that everyone would agree on.
> 
> On 03/16/2016 02:36 PM, Jerry Scharf wrote:
> > The real problem is
> > in the kernel and drivers, where you can and often have to lock out
> > interrupts. If those are not designed to work correctly and cooperatively,
> > things stop being RT. When the person writing the graphics card driver is
> > told to get as much performance as they can, they often stop thinking about
> > how polite they are to other time critical things. They have almost no
> > incentive to be careful and lots of incentive to do what makes things go
> > the fastest.
> 
> 
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Re: [Emc-users] Linuxcnc on arm

[Nicklas Karlsson]

> On 03/16/2016 11:50 AM, John Dammeyer wrote:
> > Seems that's a fault of the graphics drivers and their implementation.  The
> > whole point of an RTOS is that tasks can run at priorities that serve their
> > needs.  How would placing the video at a higher priority be any different
> > than an non-real time system that allows the video to run to completion.
> >
> >
> Some video drivers do HUGE DMA transfers between screen and 
> main memory, bursting 10's of megabytes back and forth.  
> These are totally unthrottled transfers, running as fast as 
> the memories and busses can go, and thereby locking out the 
> CPU from the memory for the duration.  Since this is not 
> caused by a process executing in the CPU, it is totally 
> beyond the control of the RT scheduler. Usually using a 
> generic video driver reduces the problem as these drivers 
> don't activate such acceleration features.
> 
> Jon

Even though huge DMA transfers currently are out of control from RT scheduler 
they should not be for good real time perfomance. I go for the micro 
controllers, slow but predictable, 25µs period run perfect because there are 
just little code to run each time.

Nicklas Karlsson

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Re: [Emc-users] Rewire Question?

[Dave Cole]

I'm not sure if it is against code or not (I would be surprised if it is 
not),  but I would run some new conduit.
Separating phases like that is a really bad idea and conduit is really 
cheap.

Dave

On 3/16/2016 12:26 PM, Todd Zuercher wrote:
> Bringing back an older thread.  Went to start ordering the things I need for 
> the update and noticed that the conduit to the machine isn't big enough for 
> the new wiring.  Right now the 9 single phase circuits are run through two 
> 3/4" conduits (4 in one 5 in the other).  would it be a really bad idea or 
> against regs, to split the 3ph wiring between the 2 conduits? (2+ground in 
> one and 1+nutral in the other)
>
> - Original Message -
> From: "Gregg Eshelman" 
> To: "Enhanced Machine Controller (EMC)" 
> Sent: Saturday, February 6, 2016 6:10:07 PM
> Subject: Re: [Emc-users] Rewire Question?
>
> On 2/6/2016 3:23 PM, Dave Cole wrote:
>> Make sure whatever you do that you have a way to lock out the main
>> breaker in the off position.
>> Osha wants to see that and it makes good sense.   Make sure you also
>> have a couple of red "lock out padlocks" around also.  Keep one with
>> your tools.
>> I had a guy come up to me and ask what I was doing just as I was packing
>> up my things after servicing a machine at a manufacturing plant.
>> The idiot who was with him ( a plant management person ) failed to
>> mention that he was an Osha enforcement guy so I explained what I had
>> done and then the Osha guy introduced himself.
>> He asked if I lockout the machines I work on and I just pointed at my
>> lock hanging on my tool bag strap and said, there's my lock. The truth
>> is that the machines are impossible to debug with the power off.  But
>> that doesn't matter, as they will happily fine you regardless.The
>> fines normally start with 4 digit numbers.
>> I don't visit that plant much any longer.   They now ship the machines
>> to another location so they can be serviced.   Their safety "rules" are
>> so difficult to deal with that it makes no sense to try and do work in
>> that plant.   For the same reason they can't keep any decent engineers
>> or technicians at that location. I predict the plant will be closing
>> within the next 5 years. The plant machinery will probably end up in
>> Mexico.
>> I'm all for being safe since it is my butt that is on the line, but
>> there is a level of common sense that must be used.
>>
>> Osha and some plants seem to forget that from time to time.
> On some other forum I read a post by a person who used to work in a shop
> when a new CNC machining center was installed.
>
>   From where the controls were, it was impossible to see the tools to jog
> them into position if the door was closed. Open the door and nothing
> could be moved.
>
> The fix was a wedge someone made to jimmy the door sensor so the
> operator could see into the machine when jogging it. It could be quickly
> removed if an inspector showed up.
>
> That's what happens when a machine is so over-saftied, it forces
> operators to disable safety systems in order to make it usable. How it
> should have been built is either with the controls mounted so that the
> operator could see into the work space while standing at them, or the
> door safety should only have locked out the spindle and turret
> rotations, while limiting axis travel to slow speeds. That would have
> made setting up quicker and safe. Select the tool, open door and set
> position. Close door and select next tool. Repeat until all tools are set.
>
>
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Re: [Emc-users] Linuxcnc on arm

[W. Martinjak]

On 2016-03-16 16:41, andy pugh wrote:
> On 16 March 2016 at 15:35, Yanjun Luo  wrote:
>> Hi,
>> I think Raspberry Pi Module 3 is a good choice, I'll try it when I get a
>> board soon
> The problem with the Pi is that the obvious choice for IO, Ethernet,
> is  connected via the USB bus.
>

But SPI works well and in conjunction with an FPGA/CPLD very well.

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Re: [Emc-users] Linuxcnc on arm

[bari]

Real time is not one of the main concerns of the kernel devs. The kernel 
has graphics drivers that interfere with real time as well as X.

On 03/16/2016 11:24 AM, John Dammeyer wrote:
> As I understand it, the MachineKit was forked from an earlier version of
> LinuxCNC and LinuxCNC requires a real time kernel to run.
>
> Why is it that the real time kernel hasn't become a basic part of Linux so
> that the orphan Linux is the one without the kernel?
>
> Surely by now we've moved past the 486DX4-100 level of processors.  IC've
> written an RTOS for an 8 bit NEC78C10, worked with VRTX RTOS on x86 CPUs and
> written software for Motorola MC68070 processors running OS9-68K.
>
>   The ARMs and current crop of PCs are orders of magnitude faster and more
> powerful so why is it that the real time part of Linux isn't the defacto
> standard for Linux.  If it were wouldn't the latest LinuxCNC run on just
> about anything?
>
> Seems a simple question.  Is there a simple answer?
>
> John Dammeyer
>


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Re: [Emc-users] Linuxcnc on arm

[andy pugh]

On 16 March 2016 at 15:52, W. Martinjak  wrote:

>> The problem with the Pi is that the obvious choice for IO, Ethernet,
>> is  connected via the USB bus.
>>
>
> But SPI works well and in conjunction with an FPGA/CPLD very well.

That might be an interesting setup with:
http://store.mesanet.com/index.php?route=product/product=83_85_id=291

-- 
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designed for the especial use of mechanical geniuses, daredevils and
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Re: [Emc-users] Linuxcnc on arm

[John Dammeyer]

Seems that's a fault of the graphics drivers and their implementation.  The
whole point of an RTOS is that tasks can run at priorities that serve their
needs.  How would placing the video at a higher priority be any different
than an non-real time system that allows the video to run to completion. 

Is the problem so simple that the RTOS system clock isn't allowed to
interrupt the video even if it's just long enough to allow the video driver
to continue to run at an elevated priority?  I can see that with older video
hardware from the early 90's but surely things are different now?

John


> Real time is not one of the main concerns of the kernel devs. The kernel
> has graphics drivers that interfere with real time as well as X.
> 
> >   The ARMs and current crop of PCs are orders of magnitude faster and
> more
> > powerful so why is it that the real time part of Linux isn't the defacto
> > standard for Linux.  If it were wouldn't the latest LinuxCNC run on just
> > about anything?
> >
> > Seems a simple question.  Is there a simple answer?
> >
> > John Dammeyer
> >
> 
> 
>

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Re: [Emc-users] Linuxcnc on arm

[andy pugh]

On 16 March 2016 at 15:35, Yanjun Luo  wrote:
> Hi,
> I think Raspberry Pi Module 3 is a good choice, I'll try it when I get a
> board soon

The problem with the Pi is that the obvious choice for IO, Ethernet,
is  connected via the USB bus.

-- 
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designed for the especial use of mechanical geniuses, daredevils and
lunatics."
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Re: [Emc-users] Stepper, ideal pulses without feedback

[Ken Johnson]

Nicklas, when I built a pcb drilling machine some years ago, I found
constant acceleration and deceleration to top speed worked best, as
for the most part trying to go instantly to the maximum speed the
motors are capable of results in lost steps.
You will need a bit of experimentation to determine the rate and
length of both acceleration ramps as it will depend on the mass of
your machine and the motors and power supply you are using.

Ken.

On Sat, Mar 19, 2016 at 5:46 AM, Nicklas Karlsson
 wrote:
> I am planning to use a micro controller for stepper step pulse generation. I 
> have considered to use an inverter card but special purpose stepper circuits 
> are cheap so I use one of these instead. It should be possible to feed timer 
> values then toggle should happen via DMA timer output compare values.
>
> Can anyone suggest how an ideal step generation curve should look? Constant 
> acceleration up to top speed? Constant deceleration from top speed to zero? 
> Or just stop generating pulses?
>
> Regards Nicklas Karlsson
>
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Re: [Emc-users] Linuxcnc on arm

[andy pugh]

On 16 March 2016 at 16:03, W. Martinjak  wrote:

> Ok, and any suggestions for the toolchain and build sequence?

Probably simplest to compile on the device itself rather than get
involved in the complexities of cross-compiling.

-- 
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designed for the especial use of mechanical geniuses, daredevils and
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Re: [Emc-users] Linuxcnc on arm

[John Dammeyer]

So how is that different from a non pre-emptive RTOS kernel?

My understanding, and it's very superficial, is that the real time component
of linux puts a scheduler in front of the basic LINUX kernel.  So now the
micro-stepping or DC-Servo/encoder support can get predictable low latency
response to events.

Building that into the kernel so that an application like LinuxCNC can
acquire the resources to get the same level of access above other hardware
seems obvious.  For a non LinuxCNC system perhaps the video or network or
serial port driver will want higher priority than default.  That's a system
configuration issue.  Not whether the scheduling by the kernel is hard real
time or soft multi-threaded.

John Dammeyer



> From: bari [mailto:bari00...@gmail.com]
> It only sort of does. If a kernel or X dev decides to access hardware
> directly to get his project done he probably will. Unfortunately there
> is no kernel police and no really agreed upon rules that they explicitly
> follow.
> 
> On 03/16/2016 12:10 PM, John Dammeyer wrote:
> > But see here's where I'm confused.  If Linux already provides priorities
of
> > tasks:
> > http://www.thegeekstuff.com/2013/08/nice-renice-command-examples/
> > then the LinuxCNC as a task can run higher than anything else.
> > If the motion/encoder control is offloaded to a device driver, which
> should
> > have even higher priority then where does the real time kernel of the
> > LinuxCNC fit in?
> > John Dammeyer
> >
> >
> 
> 
>

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Re: [Emc-users] Stepper, ideal pulses without feedback

[John Dammeyer]

You are welcome to look at my Electronic Lead Screw Code.  Follow the link
to the code.  It's written for a PIC in C.
John


"ELS! Nothing else works as well for your Lathe"
Automation Artisans Inc.
http://www.autoartisans.com/ELS/
Ph. 1 250 544 4950




> -Original Message-
> From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
> Sent: March-18-16 11:46 AM
> To: emc-users@lists.sourceforge.net
> Subject: [Emc-users] Stepper, ideal pulses without feedback
> 
> 
> I am planning to use a micro controller for stepper step pulse generation.
I
> have considered to use an inverter card but special purpose stepper
circuits
> are cheap so I use one of these instead. It should be possible to feed
timer
> values then toggle should happen via DMA timer output compare values.
> 
> Can anyone suggest how an ideal step generation curve should look?
> Constant acceleration up to top speed? Constant deceleration from top
> speed to zero? Or just stop generating pulses?
> 
> Regards Nicklas Karlsson
> 
>

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Re: [Emc-users] Linuxcnc on arm

[andy pugh]

On 16 March 2016 at 16:24, John Dammeyer  wrote:
> Why is it that the real time kernel hasn't become a basic part of Linux so
> that the orphan Linux is the one without the kernel?

With PREEMPT-RT it pretty much is.

As for why RTAI wasn't ever just built-in, I am not sure. Possibly
worries about security, as it gives very low-level access.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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Re: [Emc-users] Linuxcnc on arm

[Jcd]

So what makes the real time Linux like machine kit or for a regular PC. If 
drivers can muck things up. 

Sent from John's iPhone 4S

On 2016-03-16, at 2:05 PM, bari  wrote:

> 
> That's why we'd need the kernel police to enforce the rules, if there 
> were kernel rules that everyone would agree on.
> 
> On 03/16/2016 02:36 PM, Jerry Scharf wrote:
>> The real problem is
>> in the kernel and drivers, where you can and often have to lock out
>> interrupts. If those are not designed to work correctly and cooperatively,
>> things stop being RT. When the person writing the graphics card driver is
>> told to get as much performance as they can, they often stop thinking about
>> how polite they are to other time critical things. They have almost no
>> incentive to be careful and lots of incentive to do what makes things go
>> the fastest.
> 
> 
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Re: [Emc-users] Stepper, ideal pulses without feedback

[Nicklas Karlsson]

> > I have seen and run machinekit, it is linuxcnc. I have also read about
> > BeagleBone. There are plenty of devices suitable to generate the
> > pulses but at which rate should pulses generated? Constant
> > acceleration between different speeds?
> 
> Ideally, the accel (and decel) should be  t=rc curve or close, because at 
> the higher speeds, the motors torque is falling like a rock so the accel 
> ability is less and less as it speeds up. On slowdown the curve should 
> be reversed left for right because the motors torque is increasing as it 
> slows, so you can slow it even faster.

I think constant torque then if in flux weaking region constant power is an 
appropriate model for the motor.

> But I believe the huge majority of our controllers use pretty close to a 
> straight line ramp going either direction. If thats not the case, 
> someone please correct me.

Yes straight line: maximum velocity and maximum acceleration.

> Which said another way, speed vs acceleration is a tradeoff. I can 
> usually double the rapids achieved, but its at the cost of slower 
> acceleration, ...

If in flux weakening region I Agree. I however think most drives are used in 
constant torque region and then current model is accurate.

I however think most electrical motors are possible to overload for a short 
while. Then is the complexity for not simle kinematics.


Nicklas Karlsson

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Re: [Emc-users] Rewire Question?

[Jerry Scharf]

Todd,

I always think about the next person who has to look at my wiring. Doing
this would confuse the hell out of me if I came upon it. I might even send
unkind thoughts toward the last person and then fix the wires to be right.

Why not pull back and reroute some of the single phase wires to make space
for all the three phase wires in one conduit? When I spec down time for the
work, I just include all these tsks in the estimate.

jerry


On Wed, Mar 16, 2016 at 10:26 AM, Todd Zuercher 
wrote:

> Bringing back an older thread.  Went to start ordering the things I need
> for the update and noticed that the conduit to the machine isn't big enough
> for the new wiring.  Right now the 9 single phase circuits are run through
> two 3/4" conduits (4 in one 5 in the other).  would it be a really bad idea
> or against regs, to split the 3ph wiring between the 2 conduits? (2+ground
> in one and 1+nutral in the other)
>
> - Original Message -
> From: "Gregg Eshelman" 
> To: "Enhanced Machine Controller (EMC)" 
> Sent: Saturday, February 6, 2016 6:10:07 PM
> Subject: Re: [Emc-users] Rewire Question?
>
> On 2/6/2016 3:23 PM, Dave Cole wrote:
> > Make sure whatever you do that you have a way to lock out the main
> > breaker in the off position.
> > Osha wants to see that and it makes good sense.   Make sure you also
> > have a couple of red "lock out padlocks" around also.  Keep one with
> > your tools.
> > I had a guy come up to me and ask what I was doing just as I was packing
> > up my things after servicing a machine at a manufacturing plant.
> > The idiot who was with him ( a plant management person ) failed to
> > mention that he was an Osha enforcement guy so I explained what I had
> > done and then the Osha guy introduced himself.
> > He asked if I lockout the machines I work on and I just pointed at my
> > lock hanging on my tool bag strap and said, there's my lock. The truth
> > is that the machines are impossible to debug with the power off.  But
> > that doesn't matter, as they will happily fine you regardless.The
> > fines normally start with 4 digit numbers.
> > I don't visit that plant much any longer.   They now ship the machines
> > to another location so they can be serviced.   Their safety "rules" are
> > so difficult to deal with that it makes no sense to try and do work in
> > that plant.   For the same reason they can't keep any decent engineers
> > or technicians at that location. I predict the plant will be closing
> > within the next 5 years. The plant machinery will probably end up in
> > Mexico.
> > I'm all for being safe since it is my butt that is on the line, but
> > there is a level of common sense that must be used.
> >
> > Osha and some plants seem to forget that from time to time.
>
> On some other forum I read a post by a person who used to work in a shop
> when a new CNC machining center was installed.
>
>  From where the controls were, it was impossible to see the tools to jog
> them into position if the door was closed. Open the door and nothing
> could be moved.
>
> The fix was a wedge someone made to jimmy the door sensor so the
> operator could see into the machine when jogging it. It could be quickly
> removed if an inspector showed up.
>
> That's what happens when a machine is so over-saftied, it forces
> operators to disable safety systems in order to make it usable. How it
> should have been built is either with the controls mounted so that the
> operator could see into the work space while standing at them, or the
> door safety should only have locked out the spindle and turret
> rotations, while limiting axis travel to slow speeds. That would have
> made setting up quicker and safe. Select the tool, open door and set
> position. Close door and select next tool. Repeat until all tools are set.
>
>
> ---
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>
>
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>
>
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> 

Re: [Emc-users] Stepper, ideal pulses without feedback

[Nicklas Karlsson]

> On Friday 18 March 2016 16:00:27 Nicklas Karlsson wrote:
> 
> > I have seen and run machinekit, it is linuxcnc. I have also read about
> > BeagleBone. There are plenty of devices suitable to generate the
> > pulses but at which rate should pulses generated? Constant
> > acceleration between different speeds?
> 
> Ideally, the accel (and decel) should be  t=rc curve or close, ...

No, t=rc is for the current/torque rise/fall time. For the speed it is rather 
basic physics. Flux is needed to generate torque. Induced voltage depend on 
speed of flux change so for higher speed more voltage is induced. It is 
possible to increase speed by lowering flux but in such case maximum torque 
will sink.

Anyway as is now for a stepper I will use fast acceleration in one direction 
and slow in the other => then they line up no steps are lost at maximum 
acceleration.


Regards Nicklas Karlsson

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Re: [Emc-users] Linuxcnc on arm

[John Dammeyer]

Original Message-
> From: W. Martinjak [mailto:mats...@play-pla.net]
> 
> The problem is different.
> RT means looking around and fulfill all tasks in a defined timeslot.
> Performance means in most cases move data as fast as you can.
> And in some cases it's mutually exclusive.

So what you are saying is standard Linux is just like windows and a task
(thread, application, device driver) can take over the processor and use as
much time as it likes.  Totally co-operative rather than pre-emptive.  

That an RTOS component adds the time slicing so that every X time period a
task of equal priority gets to use that time slice or part of it to do it's
function.

Or does the first system call an application make to the OS result in an
evaluation of process priorities which results in the highest priority task
getting control which may be different from the task that called the OS.
.  
In other words a 
while (1 ) { };
  
loop will break Linux since nothing can pre-empt an infinite loop?

If that doesn't break standard Linux then there's some sort of pre-emptive
multi-tasking going on already.  

Perhaps when people use the term Real Time Linux for LinuxCNC they are
talking about something different?

John Dammeyer





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Re: [Emc-users] Stepper, ideal pulses without feedback

[John Dammeyer]

You might look at the Replicape and a BeagleBone Black.   There are several
other capes including one with a standard DB-25 parallel port that run
LinuxCNC on the Beagle.   Search for MachineKit.

John

> -Original Message-
> From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
> Sent: March-18-16 12:27 PM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Stepper, ideal pulses without feedback
> 
> 
> Nice box and standard port is always good, I should think about it.
Steppers
> are for an xyz engraver so it is essentially a mini CNC machine without
tool
> changer.
> 
> 
> 
> On Fri, 18 Mar 2016 12:00:55 -0700
> "John Dammeyer"  wrote:
> 
> > You are welcome to look at my Electronic Lead Screw Code.  Follow the
> link
> > to the code.  It's written for a PIC in C.
> > John
> >
> >
> > "ELS! Nothing else works as well for your Lathe"
> > Automation Artisans Inc.
> > http://www.autoartisans.com/ELS/
> > Ph. 1 250 544 4950
> >
> >
> >
> >
> > > -Original Message-
> > > From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
> > > Sent: March-18-16 11:46 AM
> > > To: emc-users@lists.sourceforge.net
> > > Subject: [Emc-users] Stepper, ideal pulses without feedback
> > >
> > >
> > > I am planning to use a micro controller for stepper step pulse
generation.
> > I
> > > have considered to use an inverter card but special purpose stepper
> > circuits
> > > are cheap so I use one of these instead. It should be possible to feed
> > timer
> > > values then toggle should happen via DMA timer output compare values.
> > >
> > > Can anyone suggest how an ideal step generation curve should look?
> > > Constant acceleration up to top speed? Constant deceleration from top
> > > speed to zero? Or just stop generating pulses?
> > >
> > > Regards Nicklas Karlsson
> > >
> > >
> >

> > --
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> > > Accelerate data analysis in your applications with
> > > Intel Data Analytics Acceleration Library.
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> > > https://lists.sourceforge.net/lists/listinfo/emc-users
> >
> >
> >

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> 
>

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Re: [Emc-users] Linuxcnc on arm

[W. Martinjak]

On 2016-03-16 16:28, Sebastian Kuzminsky wrote:
> We build and test on arm, but we currently don't produce debian packages.
>
> LinuxCNC 2.7 and newer work on Wheezy on armhf, you just have to build 
> it yourself:
>
> http://buildbot.linuxcnc.org/buildbot/builders/1405.rip-wheezy-armhf
>
>

Ok, and any suggestions for the toolchain and build sequence?

-- 
"In der Wissenschaft siegt nie eine neue Theorie,
nur ihre Gegner sterben nach und nach"

Max Planck


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Re: [Emc-users] Linuxcnc on arm

[Nicklas Karlsson]

Maybe they just need to read about real time scheduling to assign an approriate 
priority or do the execution in a thread with appropriate priority.

If there is a receive buffer execution should be triggered no later than half 
full and must be emptied before it may be filled. With time known to make 
buffer half full maximum periodicity is known and an appropriate priority could 
be assigned.


> It only sort of does. If a kernel or X dev decides to access hardware 
> directly to get his project done he probably will. Unfortunately there 
> is no kernel police and no really agreed upon rules that they explicitly 
> follow.
> 
> On 03/16/2016 12:10 PM, John Dammeyer wrote:
> > But see here's where I'm confused.  If Linux already provides priorities of
> > tasks:
> > http://www.thegeekstuff.com/2013/08/nice-renice-command-examples/
> > then the LinuxCNC as a task can run higher than anything else.
> > If the motion/encoder control is offloaded to a device driver, which should
> > have even higher priority then where does the real time kernel of the
> > LinuxCNC fit in?
> > John Dammeyer
> >
> >
> 
> 
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Re: [Emc-users] Stepper, ideal pulses without feedback

[Philipp Burch]

Hi Nicklas,

it should be fine to keep the step rate (velocity) constant between
updates from the trajectory planner, assuming that it runs at something
like 1kHz and the machine is not highly dynamic. Limiting velocity and
acceleration in the step generator should generally not hurt and avoids
stalled motors in case there is a step in the position command (which
should not happen with LinuxCNC unless you mess around with the signals
in HAL).

If you want to implement smooth point-to-point positioning, you could
consider some kind of jerk limiting, e.g. by using quadratic or cubic
velocity profiles (giving linear or quadratic acceleration). Or use a
sinusoidal profile, but trigo functions are computationally rather
expensive.

Regards,
Philipp

On 18.03.2016 21:15, Nicklas Karlsson wrote:
> It could be a good option so I do not need to have a large computer for a 
> small machine. As is know it is more a question about how to ideally 
> increases/decrease step rate for a stepper motor?
> 
> 
> 
> On Fri, 18 Mar 2016 16:05:31 -0400
> John Alexander Stewart  wrote:
> 
>> Just FYI - about a year ago or so I purchased from Jeff @xylotex a BBBlack
>> and DB-25 cape - ran my Unimat SL CNC'd lathe just fine (feeding a spare
>> Gecko G540, 2 axes of which were unused)
>>
>> BBBoard from Xylotex came with LinuxCNC Machinekit on a little SDCard. An
>> out of the box solution.
>>
>>
>>
>> On Fri, Mar 18, 2016 at 3:50 PM, John Dammeyer 
>> wrote:
>>
>>> You might look at the Replicape and a BeagleBone Black.   There are several
>>> other capes including one with a standard DB-25 parallel port that run
>>> LinuxCNC on the Beagle.   Search for MachineKit.
>>>
>>> John
>>>
 -Original Message-
 From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
 Sent: March-18-16 12:27 PM
 To: Enhanced Machine Controller (EMC)
 Subject: Re: [Emc-users] Stepper, ideal pulses without feedback


 Nice box and standard port is always good, I should think about it.
>>> Steppers
 are for an xyz engraver so it is essentially a mini CNC machine without
>>> tool
 changer.



 On Fri, 18 Mar 2016 12:00:55 -0700
 "John Dammeyer"  wrote:

> You are welcome to look at my Electronic Lead Screw Code.  Follow the
 link
> to the code.  It's written for a PIC in C.
> John
>
>
> "ELS! Nothing else works as well for your Lathe"
> Automation Artisans Inc.
> http://www.autoartisans.com/ELS/
> Ph. 1 250 544 4950
>
>
>
>
>> -Original Message-
>> From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
>> Sent: March-18-16 11:46 AM
>> To: emc-users@lists.sourceforge.net
>> Subject: [Emc-users] Stepper, ideal pulses without feedback
>>
>>
>> I am planning to use a micro controller for stepper step pulse
>>> generation.
> I
>> have considered to use an inverter card but special purpose stepper
> circuits
>> are cheap so I use one of these instead. It should be possible to
>>> feed
> timer
>> values then toggle should happen via DMA timer output compare values.
>>
>> Can anyone suggest how an ideal step generation curve should look?
>> Constant acceleration up to top speed? Constant deceleration from top
>> speed to zero? Or just stop generating pulses?
>>
>> Regards Nicklas Karlsson
>>
>>
>
>>>
>>> 
> --
>> Transform Data into Opportunity.
>> Accelerate data analysis in your applications with
>> Intel Data Analytics Acceleration Library.
>> Click to learn more.
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>
>
>
>>>
>>> 
>>> --
> Transform Data into Opportunity.
> Accelerate data analysis in your applications with
> Intel Data Analytics Acceleration Library.
> Click to learn more.
> http://pubads.g.doubleclick.net/gampad/clk?id=278785231=/4140
> ___
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>>>
>>> 
>>> --
 Transform Data into Opportunity.
 Accelerate data analysis in your applications with
 Intel Data Analytics Acceleration Library.
 Click to learn more.
 http://pubads.g.doubleclick.net/gampad/clk?id=278785231=/4140
 ___
 Emc-users mailing list