Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[David J Taylor]

Hal,

Thanks, this had me look closer at the outputs and not all RS232 chip 
breakout boards shift all signals, it seems to be 4-6 lines at most.
I've seen some MAX3232 (RS232 to TTL) converters, but the better ones only 
shift Rx, Tx, CTS, RTS, VCC and GND.


If I read what was suggested here earlier correctly, I need DCD for the PPS 
signal and Rx, Tx for NMEA.
I plan to use this with pfsense/gpsd which lets you choose between rising 
and falling edge for PPS signal processing.


I'll go ahead and order https://www.sparkfun.com/products/11189 as it 
appears to do all RS232 signals and can handle voltages > 5V.


Thank you all again!
==

On a couple of PCs I've installed recently, RS232 add-in boards respond to 
the 3.3V DCD signal, although not to 3.3V data lines.  This from a ublox 6M 
on a Chinese add-in board.  Whilst this would obviously be unsuitable for a 
stand-alone system, if you only need the PPS precision and have a suitable 
source of coarse second, it may be good enough.  It's working for me on a 
Windows-10 PC using the loopback_ppsapi-provider.dll.


Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv 


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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[STR .]

>The normal RS-232 level shifter chip includes an inverter.  (No good reason, 
>just historical, but with a long history.)

>I can't understand the schematic on the part Gary suggested.  I'd use 
>something like this:
>  https://www.sparkfun.com/products/11189

Hal,

Thanks, this had me look closer at the outputs and not all RS232 chip breakout 
boards shift all signals, it seems to be 4-6 lines at most.
I've seen some MAX3232 (RS232 to TTL) converters, but the better ones only 
shift Rx, Tx, CTS, RTS, VCC and GND.

If I read what was suggested here earlier correctly, I need DCD for the PPS 
signal and Rx, Tx for NMEA.
I plan to use this with pfsense/gpsd which lets you choose between rising and 
falling edge for PPS signal processing.

I'll go ahead and order https://www.sparkfun.com/products/11189 as it appears 
to do all RS232 signals and can handle voltages > 5V.


Thank you all again!
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Gary E. Miller]

Yo Hal!

albertson.ch...@gmail.com said:
> If using the PPS for timing and the PPS is inverted you will have
> to measure the delay length an account for in the config file.   

Or use gpsd to do the PPS detection.  It automagiaclly selects the
proper edge.

RGDS
GARY
---
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@rellim.com  Tel:+1 541 382 8588


pgp14VrfFkEHX.pgp
Description: OpenPGP digital signature
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Bob Camp]

Hi

Well, I have yet to test a gps module that does not have a *very* accurate
pulse width out of it. Same with GPSDO’s. Yes, It’s something I look at.

Bob

> On Nov 10, 2016, at 10:22 AM, Chris Albertson  
> wrote:
> 
> The problem here is "real world".  Yes in theory you can do it perfectly
> but in the real world do all makes and models of GPS receivers get it
> right?   I would not bet on it.
> 
> This is just like the argument over using NMEA only for timing.  Some GPS
> receivers push out NEMA sentences with very little jitter and others only
> follow the NMEA spec with only requires plus or minus one second accuracy
> and then there is every shade of grey between.
> 
> My conservative engineering background tells me that unless the variation
> of the pulse width is species you should assume the width is not controlled
> at all.  It may even look good in testing but a firmware update would kill
> that.  Likely in there is no regression test for not specified features.
> People now days who write software (or firmware especially) will build an
> automated test suit that lets them checks f the software still works after
> making changes.  They are careful to test each written requirement.
> 
> The UART on the PC can interrupt on either raising or facing edges so if
> the PPS is inverted you interrupt on the falling edge.   But you have to
> get this right too
> 
> one IMPORTENT thing to  get right is to remember that on modern control
> line under RS232 the logic is "active low".  TTL logic is "active high"
> where a higher voltage means "one" and allow voltage means "zero" but this
> is backwards for modern control under RS232   So, it is WAY-EASY to get it
> wrong when connecting a TTL PPS to a modern control line. You might
> need an inverter because many level shifters invert the signal
> 
> The one thing that helps is the at 1Hz the signal is slow enough to see on
> a volt meter, Even an old VTVM reacts fast enough
> 
> On Wed, Nov 9, 2016 at 2:44 PM, Tom Van Baak  wrote:
> 
>> Bob,
>> 
>> The PIC's I use have essentially no jitter. If they generate a 1PPS the
>> edge and the pulse width are perfect, down to picoseconds. The talk about
>> "other stuff" and "priority" and "number of compares" and "ambiguity" is
>> worrisome. It sounds like a design or coding flaw to me, like what happens
>> when people try to do precise time with a high level language.
>> 
>> /tvb
>> 
>> - Original Message -
>> From: "Bob Stewart" 
>> To: "Discussion of precise time and frequency measurement" <
>> time-nuts@febo.com>
>> Sent: Wednesday, November 09, 2016 9:30 AM
>> Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2
>> SoC serial port for ntpd
>> 
>> 
>> I'd like to comment on the idea of measuring the width of the pulse. My
>> experience with creating the 1PPS from an interrupt is that it's fairly
>> straightforward how to do the set interrupt: The interrupt happens, you
>> execute one, maybe two instructions to raise the output pin, and you leave
>> the interrupt routine. But, resetting the pin is a different story. Unless
>> you've got a lot of interrupt vectors to play with, the reset part of the
>> 1PPS signal is delegated to a general purpose timing interrupt where you're
>> doing a lot of other stuff - and it has a somewhat lower priority. So, you
>> wind up doing a number of compares to see if you should reset the pin,
>> which adds some ambiguity to the set/reset times.
>> Granted, I'm doing this on a general purpose PIC, but I have read comments
>> about various receivers having some jitter on the reset side of their 1PPS
>> pulse.
>> Bob
>> 
>> ___
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>> mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
> 
> 
> 
> -- 
> 
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Scott Stobbe]

When 1PPS is implemented as a time mark signal narrow width (versus 1 Hz
50% duty cycle) and you time stamp both edges, you can always tell which is
supposed to be the leading edge. Either the assert and deassert are close
together in the correct case or far apart when using incorrect polarity.

On Thu, Nov 10, 2016 at 10:22 AM Chris Albertson 
wrote:

> The problem here is "real world".  Yes in theory you can do it perfectly
> but in the real world do all makes and models of GPS receivers get it
> right?   I would not bet on it.
>
> This is just like the argument over using NMEA only for timing.  Some GPS
> receivers push out NEMA sentences with very little jitter and others only
> follow the NMEA spec with only requires plus or minus one second accuracy
> and then there is every shade of grey between.
>
> My conservative engineering background tells me that unless the variation
> of the pulse width is species you should assume the width is not controlled
> at all.  It may even look good in testing but a firmware update would kill
> that.  Likely in there is no regression test for not specified features.
> People now days who write software (or firmware especially) will build an
> automated test suit that lets them checks f the software still works after
> making changes.  They are careful to test each written requirement.
>
> The UART on the PC can interrupt on either raising or facing edges so if
> the PPS is inverted you interrupt on the falling edge.   But you have to
> get this right too
>
> one IMPORTENT thing to  get right is to remember that on modern control
> line under RS232 the logic is "active low".  TTL logic is "active high"
> where a higher voltage means "one" and allow voltage means "zero" but this
> is backwards for modern control under RS232   So, it is WAY-EASY to get it
> wrong when connecting a TTL PPS to a modern control line. You might
> need an inverter because many level shifters invert the signal
>
> The one thing that helps is the at 1Hz the signal is slow enough to see on
> a volt meter, Even an old VTVM reacts fast enough
>
> On Wed, Nov 9, 2016 at 2:44 PM, Tom Van Baak  wrote:
>
> > Bob,
> >
> > The PIC's I use have essentially no jitter. If they generate a 1PPS the
> > edge and the pulse width are perfect, down to picoseconds. The talk about
> > "other stuff" and "priority" and "number of compares" and "ambiguity" is
> > worrisome. It sounds like a design or coding flaw to me, like what
> happens
> > when people try to do precise time with a high level language.
> >
> > /tvb
> >
> > - Original Message -
> > From: "Bob Stewart" 
> > To: "Discussion of precise time and frequency measurement" <
> > time-nuts@febo.com>
> > Sent: Wednesday, November 09, 2016 9:30 AM
> > Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2
> > SoC serial port for ntpd
> >
> >
> > I'd like to comment on the idea of measuring the width of the pulse. My
> > experience with creating the 1PPS from an interrupt is that it's fairly
> > straightforward how to do the set interrupt: The interrupt happens, you
> > execute one, maybe two instructions to raise the output pin, and you
> leave
> > the interrupt routine. But, resetting the pin is a different story.
> Unless
> > you've got a lot of interrupt vectors to play with, the reset part of the
> > 1PPS signal is delegated to a general purpose timing interrupt where
> you're
> > doing a lot of other stuff - and it has a somewhat lower priority. So,
> you
> > wind up doing a number of compares to see if you should reset the pin,
> > which adds some ambiguity to the set/reset times.
> > Granted, I'm doing this on a general purpose PIC, but I have read
> comments
> > about various receivers having some jitter on the reset side of their
> 1PPS
> > pulse.
> > Bob
> >
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> > mailman/listinfo/time-nuts
> > and follow the instructions there.
> >
>
>
>
> --
>
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Chris Albertson]

The problem here is "real world".  Yes in theory you can do it perfectly
but in the real world do all makes and models of GPS receivers get it
right?   I would not bet on it.

This is just like the argument over using NMEA only for timing.  Some GPS
receivers push out NEMA sentences with very little jitter and others only
follow the NMEA spec with only requires plus or minus one second accuracy
and then there is every shade of grey between.

My conservative engineering background tells me that unless the variation
of the pulse width is species you should assume the width is not controlled
at all.  It may even look good in testing but a firmware update would kill
that.  Likely in there is no regression test for not specified features.
People now days who write software (or firmware especially) will build an
automated test suit that lets them checks f the software still works after
making changes.  They are careful to test each written requirement.

The UART on the PC can interrupt on either raising or facing edges so if
the PPS is inverted you interrupt on the falling edge.   But you have to
get this right too

one IMPORTENT thing to  get right is to remember that on modern control
line under RS232 the logic is "active low".  TTL logic is "active high"
where a higher voltage means "one" and allow voltage means "zero" but this
is backwards for modern control under RS232   So, it is WAY-EASY to get it
wrong when connecting a TTL PPS to a modern control line. You might
need an inverter because many level shifters invert the signal

The one thing that helps is the at 1Hz the signal is slow enough to see on
a volt meter, Even an old VTVM reacts fast enough

On Wed, Nov 9, 2016 at 2:44 PM, Tom Van Baak  wrote:

> Bob,
>
> The PIC's I use have essentially no jitter. If they generate a 1PPS the
> edge and the pulse width are perfect, down to picoseconds. The talk about
> "other stuff" and "priority" and "number of compares" and "ambiguity" is
> worrisome. It sounds like a design or coding flaw to me, like what happens
> when people try to do precise time with a high level language.
>
> /tvb
>
> - Original Message -
> From: "Bob Stewart" 
> To: "Discussion of precise time and frequency measurement" <
> time-nuts@febo.com>
> Sent: Wednesday, November 09, 2016 9:30 AM
> Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2
> SoC serial port for ntpd
>
>
> I'd like to comment on the idea of measuring the width of the pulse. My
> experience with creating the 1PPS from an interrupt is that it's fairly
> straightforward how to do the set interrupt: The interrupt happens, you
> execute one, maybe two instructions to raise the output pin, and you leave
> the interrupt routine. But, resetting the pin is a different story. Unless
> you've got a lot of interrupt vectors to play with, the reset part of the
> 1PPS signal is delegated to a general purpose timing interrupt where you're
> doing a lot of other stuff - and it has a somewhat lower priority. So, you
> wind up doing a number of compares to see if you should reset the pin,
> which adds some ambiguity to the set/reset times.
> Granted, I'm doing this on a general purpose PIC, but I have read comments
> about various receivers having some jitter on the reset side of their 1PPS
> pulse.
> Bob
>
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> time-nuts mailing list -- time-nuts@febo.com
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>



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Hal Murray]

t...@leapsecond.com said:
> The PIC's I use have essentially no jitter. If they generate a 1PPS the edge
> and the pulse width are perfect, down to picoseconds. The talk about "other
> stuff" and "priority" and "number of compares" and "ambiguity" is worrisome.
> It sounds like a design or coding flaw to me, like what happens when people
> try to do precise time with a high level language. 

It's fun to debug software with a scope.


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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Hal Murray]

albertson.ch...@gmail.com said:
> If using the PPS for timing and the PPS is inverted you will have to measure
> the delay length an account for in the config file. 

Or use the falling edge rather than the rising edge.

Most instrumentation has a knob/button/whatever to select which direction to 
trigger on.

If your "config file" refers to ntpd, the ATOM/PPS driver has a flag to use 
the falling edge.

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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Bob Stewart]

Hi Adrian,
Then I apologize for doing such a poor job of getting my meaning across.  What 
I was trying to show was that for a number of reasons, you can't necessarily 
trust the trailing edge of a 1PPS pulse.  If you're generating a pulse every 
second from a clock, and that's all your doing, then, yes, it's an easy job to 
make the pulsewidth very stable at whatever value you choose.

Bob
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Adrian Godwin 
 To: Bob Stewart ; Discussion of precise time and frequency 
measurement  
Cc: Tom Van Baak 
 Sent: Wednesday, November 9, 2016 5:39 PM
 Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
serial port for ntpd
   
But trailing isn't the same as falling. The leading edge can be of either 
polarity.


On Wed, Nov 9, 2016 at 11:28 PM, Bob Stewart  wrote:

Tom,
How many times have people posted here, on time-nuts, not to trust the trailing 
edge of a 1PPS pulse?

Bob -- -- -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/ GFS-GPSDOs/info

      From: Tom Van Baak 
 To: Discussion of precise time and frequency measurement 
 Sent: Wednesday, November 9, 2016 4:44 PM
 Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
serial port for ntpd

Bob,

The PIC's I use have essentially no jitter. If they generate a 1PPS the edge 
and the pulse width are perfect, down to picoseconds. The talk about "other 
stuff" and "priority" and "number of compares" and "ambiguity" is worrisome. It 
sounds like a design or coding flaw to me, like what happens when people try to 
do precise time with a high level language.

/tvb

- Original Message -
From: "Bob Stewart" 
To: "Discussion of precise time and frequency measurement" 
Sent: Wednesday, November 09, 2016 9:30 AM
Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
serial port for ntpd


I'd like to comment on the idea of measuring the width of the pulse. My 
experience with creating the 1PPS from an interrupt is that it's fairly 
straightforward how to do the set interrupt: The interrupt happens, you execute 
one, maybe two instructions to raise the output pin, and you leave the 
interrupt routine. But, resetting the pin is a different story. Unless you've 
got a lot of interrupt vectors to play with, the reset part of the 1PPS signal 
is delegated to a general purpose timing interrupt where you're doing a lot of 
other stuff - and it has a somewhat lower priority. So, you wind up doing a 
number of compares to see if you should reset the pin, which adds some 
ambiguity to the set/reset times.
Granted, I'm doing this on a general purpose PIC, but I have read comments 
about various receivers having some jitter on the reset side of their 1PPS 
pulse.
Bob

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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Bob Camp]

Hi


> On Nov 9, 2016, at 6:28 PM, Bob Stewart  wrote:
> 
> Tom,
> How many times have people posted here, on time-nuts, not to trust the 
> trailing edge of a 1PPS pulse? 

The rest of the caution is : The leading edge is the one that is “on time” and 
the second edge is an 
unknown offset from it …. If you have something made back in the 1950’s you 
might have an issue
with an analog one shot. 

Bob

> 
> Bob -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>  From: Tom Van Baak 
> To: Discussion of precise time and frequency measurement  
> Sent: Wednesday, November 9, 2016 4:44 PM
> Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
> serial port for ntpd
> 
> Bob,
> 
> The PIC's I use have essentially no jitter. If they generate a 1PPS the edge 
> and the pulse width are perfect, down to picoseconds. The talk about "other 
> stuff" and "priority" and "number of compares" and "ambiguity" is worrisome. 
> It sounds like a design or coding flaw to me, like what happens when people 
> try to do precise time with a high level language.
> 
> /tvb
> 
> - Original Message - 
> From: "Bob Stewart" 
> To: "Discussion of precise time and frequency measurement" 
> 
> Sent: Wednesday, November 09, 2016 9:30 AM
> Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
> serial port for ntpd
> 
> 
> I'd like to comment on the idea of measuring the width of the pulse. My 
> experience with creating the 1PPS from an interrupt is that it's fairly 
> straightforward how to do the set interrupt: The interrupt happens, you 
> execute one, maybe two instructions to raise the output pin, and you leave 
> the interrupt routine. But, resetting the pin is a different story. Unless 
> you've got a lot of interrupt vectors to play with, the reset part of the 
> 1PPS signal is delegated to a general purpose timing interrupt where you're 
> doing a lot of other stuff - and it has a somewhat lower priority. So, you 
> wind up doing a number of compares to see if you should reset the pin, which 
> adds some ambiguity to the set/reset times.
> Granted, I'm doing this on a general purpose PIC, but I have read comments 
> about various receivers having some jitter on the reset side of their 1PPS 
> pulse.
> Bob
> 
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> 
> 
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Adrian Godwin]

But trailing isn't the same as falling. The leading edge can be of either
polarity.


On Wed, Nov 9, 2016 at 11:28 PM, Bob Stewart  wrote:

> Tom,
> How many times have people posted here, on time-nuts, not to trust the
> trailing edge of a 1PPS pulse?
>
> Bob -
> AE6RV.com
>
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
>   From: Tom Van Baak 
>  To: Discussion of precise time and frequency measurement <
> time-nuts@febo.com>
>  Sent: Wednesday, November 9, 2016 4:44 PM
>  Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2
> SoC serial port for ntpd
>
> Bob,
>
> The PIC's I use have essentially no jitter. If they generate a 1PPS the
> edge and the pulse width are perfect, down to picoseconds. The talk about
> "other stuff" and "priority" and "number of compares" and "ambiguity" is
> worrisome. It sounds like a design or coding flaw to me, like what happens
> when people try to do precise time with a high level language.
>
> /tvb
>
> - Original Message -
> From: "Bob Stewart" 
> To: "Discussion of precise time and frequency measurement" <
> time-nuts@febo.com>
> Sent: Wednesday, November 09, 2016 9:30 AM
> Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2
> SoC serial port for ntpd
>
>
> I'd like to comment on the idea of measuring the width of the pulse. My
> experience with creating the 1PPS from an interrupt is that it's fairly
> straightforward how to do the set interrupt: The interrupt happens, you
> execute one, maybe two instructions to raise the output pin, and you leave
> the interrupt routine. But, resetting the pin is a different story. Unless
> you've got a lot of interrupt vectors to play with, the reset part of the
> 1PPS signal is delegated to a general purpose timing interrupt where you're
> doing a lot of other stuff - and it has a somewhat lower priority. So, you
> wind up doing a number of compares to see if you should reset the pin,
> which adds some ambiguity to the set/reset times.
> Granted, I'm doing this on a general purpose PIC, but I have read comments
> about various receivers having some jitter on the reset side of their 1PPS
> pulse.
> Bob
>
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>
>
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Bob Stewart]

Tom,
How many times have people posted here, on time-nuts, not to trust the trailing 
edge of a 1PPS pulse? 

Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Tom Van Baak 
 To: Discussion of precise time and frequency measurement  
 Sent: Wednesday, November 9, 2016 4:44 PM
 Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
serial port for ntpd
   
Bob,

The PIC's I use have essentially no jitter. If they generate a 1PPS the edge 
and the pulse width are perfect, down to picoseconds. The talk about "other 
stuff" and "priority" and "number of compares" and "ambiguity" is worrisome. It 
sounds like a design or coding flaw to me, like what happens when people try to 
do precise time with a high level language.

/tvb

- Original Message - 
From: "Bob Stewart" 
To: "Discussion of precise time and frequency measurement" 
Sent: Wednesday, November 09, 2016 9:30 AM
Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
serial port for ntpd


I'd like to comment on the idea of measuring the width of the pulse. My 
experience with creating the 1PPS from an interrupt is that it's fairly 
straightforward how to do the set interrupt: The interrupt happens, you execute 
one, maybe two instructions to raise the output pin, and you leave the 
interrupt routine. But, resetting the pin is a different story. Unless you've 
got a lot of interrupt vectors to play with, the reset part of the 1PPS signal 
is delegated to a general purpose timing interrupt where you're doing a lot of 
other stuff - and it has a somewhat lower priority. So, you wind up doing a 
number of compares to see if you should reset the pin, which adds some 
ambiguity to the set/reset times.
Granted, I'm doing this on a general purpose PIC, but I have read comments 
about various receivers having some jitter on the reset side of their 1PPS 
pulse.
Bob

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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Tom Van Baak]

Bob,

The PIC's I use have essentially no jitter. If they generate a 1PPS the edge 
and the pulse width are perfect, down to picoseconds. The talk about "other 
stuff" and "priority" and "number of compares" and "ambiguity" is worrisome. It 
sounds like a design or coding flaw to me, like what happens when people try to 
do precise time with a high level language.

/tvb

- Original Message - 
From: "Bob Stewart" 
To: "Discussion of precise time and frequency measurement" 
Sent: Wednesday, November 09, 2016 9:30 AM
Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
serial port for ntpd


I'd like to comment on the idea of measuring the width of the pulse. My 
experience with creating the 1PPS from an interrupt is that it's fairly 
straightforward how to do the set interrupt: The interrupt happens, you execute 
one, maybe two instructions to raise the output pin, and you leave the 
interrupt routine. But, resetting the pin is a different story. Unless you've 
got a lot of interrupt vectors to play with, the reset part of the 1PPS signal 
is delegated to a general purpose timing interrupt where you're doing a lot of 
other stuff - and it has a somewhat lower priority. So, you wind up doing a 
number of compares to see if you should reset the pin, which adds some 
ambiguity to the set/reset times.
Granted, I'm doing this on a general purpose PIC, but I have read comments 
about various receivers having some jitter on the reset side of their 1PPS 
pulse.
Bob

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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Bob Stewart]

I'd like to comment on the idea of measuring the width of the pulse.  My 
experience with creating the 1PPS from an interrupt is that it's fairly 
straightforward how to do the set interrupt:  The interrupt happens, you 
execute one, maybe two instructions to raise the output pin, and you leave the 
interrupt routine.  But, resetting the pin is a different story.  Unless you've 
got a lot of interrupt vectors to play with, the reset part of the 1PPS signal 
is delegated to a general purpose timing interrupt where you're doing a lot of 
other stuff - and it has a somewhat lower priority.  So, you wind up doing a 
number of compares to see if you should reset the pin, which adds some 
ambiguity to the set/reset times.
Granted, I'm doing this on a general purpose PIC, but I have read comments 
about various receivers having some jitter on the reset side of their 1PPS 
pulse.
Bob
 -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Chris Albertson 
 To: Discussion of precise time and frequency measurement  
 Sent: Wednesday, November 9, 2016 10:41 AM
 Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
serial port for ntpd
   
On Tue, Nov 8, 2016 at 11:08 PM, Hal Murray  wrote:

>
> g...@rellim.com said:
> > Who cares if the PPS is inverted?
>

If the signal is NOT inverted then the raising edge will be within
nanoseconds of the UTC seconds "tick".    The inverted PPS will have the
edge delayed somewhat.  It is not even clear if the length of the delay is
constant.

If using the PPS for timing and the PPS is inverted you will have to
measure the delay length an account for in the config file.




-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Scott Stobbe]

FWIW, the 16450 uart can interrupt on any modem line change, whether it be
rising or falling.

On Wed, Nov 9, 2016 at 11:41 AM, Chris Albertson 
wrote:

> On Tue, Nov 8, 2016 at 11:08 PM, Hal Murray 
> wrote:
>
> >
> > g...@rellim.com said:
> > > Who cares if the PPS is inverted?
> >
>
> If the signal is NOT inverted then the raising edge will be within
> nanoseconds of the UTC seconds "tick".The inverted PPS will have the
> edge delayed somewhat.   It is not even clear if the length of the delay is
> constant.
>
> If using the PPS for timing and the PPS is inverted you will have to
> measure the delay length an account for in the config file.
>
>
>
>
> --
>
> Chris Albertson
> Redondo Beach, California
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Chris Albertson]

On Tue, Nov 8, 2016 at 11:08 PM, Hal Murray  wrote:

>
> g...@rellim.com said:
> > Who cares if the PPS is inverted?
>

If the signal is NOT inverted then the raising edge will be within
nanoseconds of the UTC seconds "tick".The inverted PPS will have the
edge delayed somewhat.   It is not even clear if the length of the delay is
constant.

If using the PPS for timing and the PPS is inverted you will have to
measure the delay length an account for in the config file.




-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Scott Stobbe]

Just make sure you get a board with more than one Rx/Tx pair, unless you
are happy with two boards; one for Rx/Tx and one for PPS.

On Wed, Nov 9, 2016 at 2:08 AM, Hal Murray  wrote:

>
> g...@rellim.com said:
> > Who cares if the PPS is inverted?
>
> Good point.  I wasn't paying attention to the PPS only context in the
> subject.  I keep forgetting which way is best for PPS.  Fortunately, all
> the
> software I've used knows how to handle inverted PPS.
>
> The original message in this thread also mentioned RX and TX.
>
> I'd probably get the RS-232 version since I'm likely to want the RX/TX too
> and it's more likely to be useful on other projects.
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Hal Murray]

g...@rellim.com said:
> Who cares if the PPS is inverted? 

Good point.  I wasn't paying attention to the PPS only context in the 
subject.  I keep forgetting which way is best for PPS.  Fortunately, all the 
software I've used knows how to handle inverted PPS.

The original message in this thread also mentioned RX and TX.

I'd probably get the RS-232 version since I'm likely to want the RX/TX too 
and it's more likely to be useful on other projects.


-- 
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Chris Albertson]

The MAX3223 chip does exactly what you need.  It converts 3.3 volt serial
to RS232 levels.

You can buy just the chip and add a few passives to a perf board and make
what you need or buy a little PCB with the parts already soldered down like
this
http://www.ebay.com/itm/RS232-To-TTL-Converter-Module-Serial-Module-DB9-Connector...


It is actually cheaper to buy the little PCB then to buy the parts to make
one

On Tue, Nov 8, 2016 at 7:23 PM, STR .  wrote:

> >The signals on the DB9 connector are at RS232 levels, your GPS module is
> likely 3V3 CMOS, you will need to make a level translator if you wish to
> use a standard PC >RS232 serial port.
>
> Would this do the trick? - http://www.banggood.com/8-Channel-Logic-Level-
> Translator-Converter-Bi-Directional-Module-p-1023173.html
> I'll get some 3.3 and 5 V power supplies too.
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-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Cube Central]

I've used that sparkfun part to great success...  Works like a charm.  Highly 
recommended!

-Randal R.
(at CubeCentral)

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray
Sent: Tuesday, 08 November, 2016 22:13
To: Discussion of precise time and frequency measurement 
Cc: hmur...@megapathdsl.net
Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
serial port for ntpd


stry...@hotmail.com said:
> Would this do the trick? - 
> http://www.banggood.com/8-Channel-Logic-Level-Tran
> slator-Converter-Bi-Directional-Module-p-1023173.html

Not likely.

The normal RS-232 level shifter chip includes an inverter.  (No good reason, 
just historical, but with a long history.)

I can't understand the schematic on the part Gary suggested.  I'd use something 
like this:
  https://www.sparkfun.com/products/11189


-- 
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Gary E. Miller]

Yo Hal!

On Tue, 08 Nov 2016 21:13:05 -0800
Hal Murray  wrote:

> stry...@hotmail.com said:
> > Would this do the trick? -
> > http://www.banggood.com/8-Channel-Logic-Level-Tran
> > slator-Converter-Bi-Directional-Module-p-1023173.html   
> 
> Not likely.
> 
> The normal RS-232 level shifter chip includes an inverter.  (No good
> reason, just historical, but with a long history.)

Who cares if the PPS is inverted?

> I can't understand the schematic on the part Gary suggested.  I'd use 
> something like this:
>   https://www.sparkfun.com/products/11189

I admit to not spending a lot of time on my suggestion.  Yours may well
be better.

RGDS
GARY
---
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@rellim.com  Tel:+1 541 382 8588


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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Hal Murray]

stry...@hotmail.com said:
> Would this do the trick? - http://www.banggood.com/8-Channel-Logic-Level-Tran
> slator-Converter-Bi-Directional-Module-p-1023173.html 

Not likely.

The normal RS-232 level shifter chip includes an inverter.  (No good reason, 
just historical, but with a long history.)

I can't understand the schematic on the part Gary suggested.  I'd use 
something like this:
  https://www.sparkfun.com/products/11189


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Gary E. Miller]

Yo STR!

On Wed, 9 Nov 2016 03:23:59 +
"STR ."  wrote:

> >The signals on the DB9 connector are at RS232 levels, your GPS
> >module is likely 3V3 CMOS, you will need to make a level translator
> >if you wish to use a standard PC >RS232 serial port.  
> 
> Would this do the trick? -
> http://www.banggood.com/8-Channel-Logic-Level-Translator-Converter-Bi-Directional-Module-p-1023173.html
> I'll get some 3.3 and 5 V power supplies too.


Marginal.  Remember RS-232 is +/- 12V.  Your part only gets you to 5V.

Some RS-232 ports will work with 5V, some not, and others will be flakey.

You want something like this:

https://www.sparkfun.com/products/8780


RGDS
GARY
---
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@rellim.com  Tel:+1 541 382 8588


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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[STR .]

>The signals on the DB9 connector are at RS232 levels, your GPS module is 
>likely 3V3 CMOS, you will need to make a level translator if you wish to use a 
>standard PC >RS232 serial port.

Would this do the trick? - 
http://www.banggood.com/8-Channel-Logic-Level-Translator-Converter-Bi-Directional-Module-p-1023173.html
I'll get some 3.3 and 5 V power supplies too.
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Scott Stobbe]

The signals on the DB9 connector are at RS232 levels, your GPS module is
likely 3V3 CMOS, you will need to make a level translator if you wish to
use a standard PC RS232 serial port.

On Thu, Nov 3, 2016 at 12:58 PM, STR .  wrote:

> Hello again list and Paul,
>
> The USB and Mini-PCIe converters I ordered from Ebay China have not shown
> up
> yet.
> It appears PC Engines may take a while to release the custom BIOS that
> exposes UART3 and 4 on the APU2  :/
>
> In the interest of getting this working without waiting on a BIOS I will
> try
> connecting it to COM1, which is wired to the DB9 connector.
> https://pcengines.ch/pdf/apu2.pdf
>
> Before I fry a 3.3V board with 5V signals, I hoped to ask here and confirm
> my ideas.
>
>
> Do I cross RX and TX lines from the GPS pins to the RX/TX on the DB9/COM1
> connector?
> And straight connect the PPS line from the GPS to the DCD pin on the
> DB9/COM1 connector?
>
> GPS:
> http://pcengines.info/forums/?page=post=B4D54F22-8224-
> 4A67-9F9E-85F988A1F
> 888
>
>
>
> Thanks!
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[STR .]

Hello again list and Paul,

The USB and Mini-PCIe converters I ordered from Ebay China have not shown up
yet.
It appears PC Engines may take a while to release the custom BIOS that
exposes UART3 and 4 on the APU2  :/

In the interest of getting this working without waiting on a BIOS I will try
connecting it to COM1, which is wired to the DB9 connector.
https://pcengines.ch/pdf/apu2.pdf

Before I fry a 3.3V board with 5V signals, I hoped to ask here and confirm
my ideas.


Do I cross RX and TX lines from the GPS pins to the RX/TX on the DB9/COM1
connector?
And straight connect the PPS line from the GPS to the DCD pin on the
DB9/COM1 connector?

GPS:
http://pcengines.info/forums/?page=post=B4D54F22-8224-4A67-9F9E-85F988A1F
888



Thanks!
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[STR .]

> [I'm responding to the list in case I need correcting]

>You started with NTP and my responses have all been in that context.  The 
>Soekris modification is an example of time-nut pursuit of a goal.  A side 
>effect was a very good NTP local clock.  If you goal is a very good local 
>clock then that's an approach.  If you goal is time transfer using NTP over 
>ethernet then it's >over-kill.  I'm not sure of your  goal.
>Modern replacements for the 4501 have been discussed previously.  E.g. the 
>BeagleBone Black can be clocked externally and has co-processors that can do 
>hi-res time stamps independent of the primary CPU.

Not at all Paul, my original question was about the APU2, I plan to use it as a 
router and I thought the GPS would be a fun addition.
The discussion sort of veered towards PTP and I apologize, I should've changed 
the subject to match.
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Scott Stobbe]

Certainly could work, I give the author credit for saving one gps module
from e-waste. Hopefully the USB drivers for the ublox module will provide a
virtual com port, then all you have to worry about is wiring the PPS line.

On Tue, Aug 23, 2016 at 2:40 AM, STR .  wrote:

> Could another way be to cut out the mini-pci interface like
> http://galeria.tech-blog.pl/U-blox_PCI-5S_GPS/U-blox_PCI-5S_
> GPS_10.jpg.html though I'm not sure if he's driving it via serial?
>
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Scott
> Stobbe
> Sent: Monday, August 22, 2016 10:46 PM
> To: Discussion of precise time and frequency measurement <
> time-nuts@febo.com>
> Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2
> SoC serial port for ntpd
>
> The mini-PCI Express Card specification includes quite a bit more than
> just a single PCI-Express lane, there is also provisions for I2C (smbus),
> USB, LEDs, SIM, etc... While without looking a the physical card or
> specification I can't be certain, but I highly doubt it implements a
> PCI-Express interface. It is surely just using the USB interface over the
> express card slot. The GPS card should enumerate over the USB bus without
> any issues. In windows, ublox should provide you with USB drivers for their
> modules.
>
> You will have to experiment to see if the RX/TX lines of the GPS module
> are active after a POR, or if it defaults to USB, as that is how it was
> intended to be used. But the PPS line definitely needs to be connected to
> one of modem control lines of a UART.
>
> On Sun, Aug 21, 2016 at 11:30 AM, STR .  wrote:
>
> > Thank you!
> > Your post has made my choices clear, UART-c might be it!
> > A previous poster said there'd be no difference in jitter using any of
> > the
> > 4 COM ports and this was reassuring.
> > I will start studying the pinouts to confirm the pin numbers while I
> > wait for the null-modem cable to arrive.
> >
> > Another question, would connecting PPS, Tx/Rx to the GPIO pins on
> > UART-c make U-blox's Windows u-Center software see this as attached to
> > a physical serial port?
> > If not, how would I present the GPS to Windows via serial?
> > I'd like to test updating the firmware and it appears to not work via
> > a mini-pci to WWAN 3G USB adapter.
> >
> > Others have reported:
> > "After Emeryth published the pinout, I also started to experiment with
> > this board. I found out that you can update the firmware using the
> > LEA-5 firmware version 6.02 from the u-blox web site. The module also
> > works very well with the patched firmware version EXT_G50_602_LEA-5H.
> > bdbfccefb9dbd8395dec7adece53c1f9.bin. This version enables the output
> > of raw data for use with rtklib for real-time kinematic and precision
> > positioning.
> >
> > You can then use the standard drivers from the u-blox web site for
> > Windows. They provide a virtual COM port. Please note that updating
> > the firmware just worked using the physical serial port of the
> > Mini-PCIe card, it did not work using the USB adapter."
> >
> >
> >
> > -Original Message-
> > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Paul
> > Sent: Tuesday, August 16, 2016 2:27 AM
> > To: Discussion of precise time and frequency measurement <
> > time-nuts@febo.com>
> > Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to
> > APU2 SoC serial port for ntpd
> >
> > On Mon, Aug 15, 2016 at 5:35 AM, STR .  wrote:
> >
> > > Pardon my ignorance, I'm not sure what COM port the PPS is tied to
> > > or what you mean.
> >
> >
> > I think there's some confusion.
> >
> > Normally the PPS input to Linux (I'm not sure about FreeBSD) is tied
> > to the DCD pin in a serial port.  The PPS code is connected to the
> > interrupt from the DCD.  It can be tied to another pin (DSR or CTS I
> > forget), a parallel port or a GPIO pin (a la RaspberryPi or
> > BeagleBone).  Anything other than DCD normally requires a specific
> > kernel build.  The APU2c has an I/O part connected via an LPC bus.
> > It's essentially 4 UARTS.  UART-a is connected to a DE-9 connector via
> > a level shifter.  All signals are present.  UART-b is brought to J3
> > unshifted.  Even though J3 has five pins only transmit, receive and
> > ground are connected.  UARTs "c" and "d" are brought to J17 either as
> > 18 GPIO signals or 2x8 RS-232 signals (the latter requires
> > non-standard bios code to set up the chip).  So if we imagine that you
> > want to use the DCD pin on UART-c you'd configure the GPIO pins as
> > serial and connect to pin 9 on J17.  Be advised that the specifics in
> the previous may be wrong so check the schematic.
> >
> > Now if you want to read the correct time as a sentence from the GPS
> > you'd connect the Tx/Rx pins on your module to the corresponding pins
> > on a 3V3 serial port.  Continuing to use UART-c that would be pins 7 and
> 8 on 

Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Paul]

[I'm responding to the list in case I need correcting]

On Tue, Aug 23, 2016 at 3:03 AM, STR .  wrote:

> Old net4501's are inexpensive, they do occasionally pop up on ebay for
> around $20-40 but as making the TAPR Clock-Block is not something I can do
> I never bought a 4501.
>

 You started with NTP and my responses have all been in that context.  The
Soekris modification is an example of time-nut pursuit of a goal.  A side
effect was a very good NTP local clock.  If you goal is a very good local
clock then that's an approach.  If you goal is time transfer using NTP over
ethernet then it's over-kill.  I'm not sure of your  goal.

Modern replacements for the 4501 have been discussed previously.  E.g. the
BeagleBone Black can be clocked externally and has co-processors that can
do hi-res time stamps independent of the primary CPU.
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[STR .]

> Most GBit NIC have hardware timestamping these days. Though I don't know if 
> whether the APU NICs do.

I found 6 Intel 1G NICs that list PTP (IEEE 1588) in their specs - Intel 82574, 
82576, 82580, I340, I350 and the I210 - 
https://communities.intel.com/community/wired/blog/2011/07/07/ieee-1588-update
Of those only 1 appears to do hardware timestamping for all Ethernet 
traffic(??) not just PTP - the Intel I340 - 
https://communities.intel.com/thread/87751

It appears the APU2 c4 model (which I have) has the Intel I210 NICs which do 
PTP, I'll check with Pascal/PC Engines if this is true.
As you and others have said the APU2+GPS via serial won't be a time-nuts 
standard time server, this isn't the time/clock source for adding a PTP switch 
to serve PTP NICs on the LAN. In time, perhaps :)

>From 
>http://www.intel.com/content/www/us/en/embedded/products/networking/i210-ethernet-controller-datasheet.html
Advanced Features:
—  Audio-video bridging
• IEEE 1588/802.1AS precision time synchronization

Time-nuts standards require implementations and physics/electronics knowhow 
that are way beyond me, I'm happy to lurk, learn and implement what little I 
can.
The lack of older, now inexpensive frequency standards hardware availability 
locally here is another barrier besides their shipping weight.
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[David J Taylor]

From: STR .

Not even ethernet with hardware PTP implementations, admittedly I haven't 
seen a NIC for sale with it?
I've always wondered if something like 
https://store.uputronics.com/index.php?route=product/product=60_70_id=92 
is worth the price over the likes of 
http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm

___


The LeoNTP is a generation later, lower-power, has Ethernet, doesn't require 
serial, can be powered over USB or Ethernet, likely has a more sensitive GPS 
receiver, can service many clients for NTP etc. etc.  I think they are aimed 
at slightly different markets.  The quoted price is GPB 250 for the LeoNTP 
and GBP 260 for the Miller, but the Miller may include UK tax and the LeoNTP 
not.  If the Miller price includes UK tax, the comparison is GBP 260 Miller, 
GBP 300 LeoNTP.  Much as I would like to support another radio amateur's 
efforts, I think the LeoNTP outclasses the Miller.


If you only need a programmable, dual-output GPS-locked frequency source, at 
GBP 150 (including tax?):


 http://www.leobodnar.com/shop/index.php?main_page=product_info_id=234

Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv 


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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Attila Kinali]

On Tue, 23 Aug 2016 07:11:23 +
"STR ."  wrote:

> > Unless time-nuts levels of precision/accuracy are required, an APU is good 
> > enough and an easy solution. If you go for time-nuts levels, then I would 
> > question the use > of ethernet long before I question the hardware platform.
> 
> Not even ethernet with hardware PTP implementations, admittedly I haven't 
> seen a NIC for sale with it?

Most GBit NIC have hardware timestamping these days. Though I don't know
if whether the APU NICs do.

But even with hardware timestamping, you will not get to time-nuts levels,
which are lower than you think :-)
With standard networking equipment, you will not get below a 1-100us
uncertainty. Although this is quite good and usually enough for most
people, it's not time-nuts. A time-nuts strives for low-ns or even sub-ns
level of synchronization. With the proper equipment you can achieve
better than 10ps within a building.

Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[STR .]

> Unless time-nuts levels of precision/accuracy are required, an APU is good 
> enough and an easy solution. If you go for time-nuts levels, then I would 
> question the use > of ethernet long before I question the hardware platform.

Not even ethernet with hardware PTP implementations, admittedly I haven't seen 
a NIC for sale with it?
I've always wondered if something like 
https://store.uputronics.com/index.php?route=product/product=60_70_id=92
 is worth the price over the likes of 
http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm 
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[STR .]

> Finally, these boxes are intended to be routers (hence the three network
> interfaces) not time-servers and unless you're irrevocably wedded to the 
> miniPCIe in APU2 route there are probably better choices for time servers.

Paul,

John Ackermann's post on using the Soekris net4501 is what opened my eyes to 
GPSDO back then, sadly the TAPR Clock-Block clock synthesizer has not been 
available for sale since many years, although the FatPPS signal conditioner is.
Old net4501's are inexpensive, they do occasionally pop up on ebay for around 
$20-40 but as making the TAPR Clock-Block is not something I can do I never 
bought a 4501.

Is there an alternate replacement for the Clock-Block today? The soldering is 
out of my league but nothing the local TV/radio shop couldn't handle.
The net 4501 price today totally justifies another ntpd :)
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[STR .]

Could another way be to cut out the mini-pci interface like 
http://galeria.tech-blog.pl/U-blox_PCI-5S_GPS/U-blox_PCI-5S_GPS_10.jpg.html 
though I'm not sure if he's driving it via serial?


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Scott Stobbe
Sent: Monday, August 22, 2016 10:46 PM
To: Discussion of precise time and frequency measurement 
Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
serial port for ntpd

The mini-PCI Express Card specification includes quite a bit more than just a 
single PCI-Express lane, there is also provisions for I2C (smbus), USB, LEDs, 
SIM, etc... While without looking a the physical card or specification I can't 
be certain, but I highly doubt it implements a PCI-Express interface. It is 
surely just using the USB interface over the express card slot. The GPS card 
should enumerate over the USB bus without any issues. In windows, ublox should 
provide you with USB drivers for their modules.

You will have to experiment to see if the RX/TX lines of the GPS module are 
active after a POR, or if it defaults to USB, as that is how it was intended to 
be used. But the PPS line definitely needs to be connected to one of modem 
control lines of a UART.

On Sun, Aug 21, 2016 at 11:30 AM, STR .  wrote:

> Thank you!
> Your post has made my choices clear, UART-c might be it!
> A previous poster said there'd be no difference in jitter using any of 
> the
> 4 COM ports and this was reassuring.
> I will start studying the pinouts to confirm the pin numbers while I 
> wait for the null-modem cable to arrive.
>
> Another question, would connecting PPS, Tx/Rx to the GPIO pins on 
> UART-c make U-blox's Windows u-Center software see this as attached to 
> a physical serial port?
> If not, how would I present the GPS to Windows via serial?
> I'd like to test updating the firmware and it appears to not work via 
> a mini-pci to WWAN 3G USB adapter.
>
> Others have reported:
> "After Emeryth published the pinout, I also started to experiment with 
> this board. I found out that you can update the firmware using the 
> LEA-5 firmware version 6.02 from the u-blox web site. The module also 
> works very well with the patched firmware version EXT_G50_602_LEA-5H.
> bdbfccefb9dbd8395dec7adece53c1f9.bin. This version enables the output 
> of raw data for use with rtklib for real-time kinematic and precision 
> positioning.
>
> You can then use the standard drivers from the u-blox web site for 
> Windows. They provide a virtual COM port. Please note that updating 
> the firmware just worked using the physical serial port of the 
> Mini-PCIe card, it did not work using the USB adapter."
>
>
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Paul
> Sent: Tuesday, August 16, 2016 2:27 AM
> To: Discussion of precise time and frequency measurement < 
> time-nuts@febo.com>
> Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to 
> APU2 SoC serial port for ntpd
>
> On Mon, Aug 15, 2016 at 5:35 AM, STR .  wrote:
>
> > Pardon my ignorance, I'm not sure what COM port the PPS is tied to 
> > or what you mean.
>
>
> I think there's some confusion.
>
> Normally the PPS input to Linux (I'm not sure about FreeBSD) is tied 
> to the DCD pin in a serial port.  The PPS code is connected to the 
> interrupt from the DCD.  It can be tied to another pin (DSR or CTS I 
> forget), a parallel port or a GPIO pin (a la RaspberryPi or 
> BeagleBone).  Anything other than DCD normally requires a specific 
> kernel build.  The APU2c has an I/O part connected via an LPC bus.  
> It's essentially 4 UARTS.  UART-a is connected to a DE-9 connector via 
> a level shifter.  All signals are present.  UART-b is brought to J3 
> unshifted.  Even though J3 has five pins only transmit, receive and 
> ground are connected.  UARTs "c" and "d" are brought to J17 either as 
> 18 GPIO signals or 2x8 RS-232 signals (the latter requires 
> non-standard bios code to set up the chip).  So if we imagine that you 
> want to use the DCD pin on UART-c you'd configure the GPIO pins as 
> serial and connect to pin 9 on J17.  Be advised that the specifics in the 
> previous may be wrong so check the schematic.
>
> Now if you want to read the correct time as a sentence from the GPS 
> you'd connect the Tx/Rx pins on your module to the corresponding pins 
> on a 3V3 serial port.  Continuing to use UART-c that would be pins 7 and 8 on 
> J17.
>
> Now regarding jitter.  Pascal suggests that the jitter involved in 
> using his take on the LPC connected super i/o part might be too high.  
> As noted someone said that was the case with the APU1.  While I 
> wouldn't be surprised if that were still true with the APU2 you might 
> find the time "good enough".  Trust but verify.
>
> Finally, these boxes are intended to be routers (hence the three 
> network
> interfaces) 

Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[STR .]

I bought 2 of these just in case I trash one while updating the firmware.
If it doesn't work in the APU, I could order a mini-PCI to PCI converter 
adapter and see if I can get the other one going in a desktop.


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Scott Stobbe
Sent: Monday, August 22, 2016 10:46 PM
To: Discussion of precise time and frequency measurement 
Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
serial port for ntpd

The mini-PCI Express Card specification includes quite a bit more than just a 
single PCI-Express lane, there is also provisions for I2C (smbus), USB, LEDs, 
SIM, etc... While without looking a the physical card or specification I can't 
be certain, but I highly doubt it implements a PCI-Express interface. It is 
surely just using the USB interface over the express card slot. The GPS card 
should enumerate over the USB bus without any issues. In windows, ublox should 
provide you with USB drivers for their modules.

You will have to experiment to see if the RX/TX lines of the GPS module are 
active after a POR, or if it defaults to USB, as that is how it was intended to 
be used. But the PPS line definitely needs to be connected to one of modem 
control lines of a UART.

On Sun, Aug 21, 2016 at 11:30 AM, STR .  wrote:

> Thank you!
> Your post has made my choices clear, UART-c might be it!
> A previous poster said there'd be no difference in jitter using any of 
> the
> 4 COM ports and this was reassuring.
> I will start studying the pinouts to confirm the pin numbers while I 
> wait for the null-modem cable to arrive.
>
> Another question, would connecting PPS, Tx/Rx to the GPIO pins on 
> UART-c make U-blox's Windows u-Center software see this as attached to 
> a physical serial port?
> If not, how would I present the GPS to Windows via serial?
> I'd like to test updating the firmware and it appears to not work via 
> a mini-pci to WWAN 3G USB adapter.
>
> Others have reported:
> "After Emeryth published the pinout, I also started to experiment with 
> this board. I found out that you can update the firmware using the 
> LEA-5 firmware version 6.02 from the u-blox web site. The module also 
> works very well with the patched firmware version EXT_G50_602_LEA-5H.
> bdbfccefb9dbd8395dec7adece53c1f9.bin. This version enables the output 
> of raw data for use with rtklib for real-time kinematic and precision 
> positioning.
>
> You can then use the standard drivers from the u-blox web site for 
> Windows. They provide a virtual COM port. Please note that updating 
> the firmware just worked using the physical serial port of the 
> Mini-PCIe card, it did not work using the USB adapter."
>
>
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Paul
> Sent: Tuesday, August 16, 2016 2:27 AM
> To: Discussion of precise time and frequency measurement < 
> time-nuts@febo.com>
> Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to 
> APU2 SoC serial port for ntpd
>
> On Mon, Aug 15, 2016 at 5:35 AM, STR .  wrote:
>
> > Pardon my ignorance, I'm not sure what COM port the PPS is tied to 
> > or what you mean.
>
>
> I think there's some confusion.
>
> Normally the PPS input to Linux (I'm not sure about FreeBSD) is tied 
> to the DCD pin in a serial port.  The PPS code is connected to the 
> interrupt from the DCD.  It can be tied to another pin (DSR or CTS I 
> forget), a parallel port or a GPIO pin (a la RaspberryPi or 
> BeagleBone).  Anything other than DCD normally requires a specific 
> kernel build.  The APU2c has an I/O part connected via an LPC bus.  
> It's essentially 4 UARTS.  UART-a is connected to a DE-9 connector via 
> a level shifter.  All signals are present.  UART-b is brought to J3 
> unshifted.  Even though J3 has five pins only transmit, receive and 
> ground are connected.  UARTs "c" and "d" are brought to J17 either as 
> 18 GPIO signals or 2x8 RS-232 signals (the latter requires 
> non-standard bios code to set up the chip).  So if we imagine that you 
> want to use the DCD pin on UART-c you'd configure the GPIO pins as 
> serial and connect to pin 9 on J17.  Be advised that the specifics in the 
> previous may be wrong so check the schematic.
>
> Now if you want to read the correct time as a sentence from the GPS 
> you'd connect the Tx/Rx pins on your module to the corresponding pins 
> on a 3V3 serial port.  Continuing to use UART-c that would be pins 7 and 8 on 
> J17.
>
> Now regarding jitter.  Pascal suggests that the jitter involved in 
> using his take on the LPC connected super i/o part might be too high.  
> As noted someone said that was the case with the APU1.  While I 
> wouldn't be surprised if that were still true with the APU2 you might 
> find the time "good enough".  Trust but verify.
>
> Finally, these boxes are intended to be routers (hence the three 
> 

Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Scott Stobbe]

The mini-PCI Express Card specification includes quite a bit more than just
a single PCI-Express lane, there is also provisions for I2C (smbus), USB,
LEDs, SIM, etc... While without looking a the physical card or
specification I can't be certain, but I highly doubt it implements a
PCI-Express interface. It is surely just using the USB interface over the
express card slot. The GPS card should enumerate over the USB bus without
any issues. In windows, ublox should provide you with USB drivers for their
modules.

You will have to experiment to see if the RX/TX lines of the GPS module are
active after a POR, or if it defaults to USB, as that is how it was
intended to be used. But the PPS line definitely needs to be connected to
one of modem control lines of a UART.

On Sun, Aug 21, 2016 at 11:30 AM, STR .  wrote:

> Thank you!
> Your post has made my choices clear, UART-c might be it!
> A previous poster said there'd be no difference in jitter using any of the
> 4 COM ports and this was reassuring.
> I will start studying the pinouts to confirm the pin numbers while I wait
> for the null-modem cable to arrive.
>
> Another question, would connecting PPS, Tx/Rx to the GPIO pins on UART-c
> make U-blox's Windows u-Center software see this as attached to a physical
> serial port?
> If not, how would I present the GPS to Windows via serial?
> I'd like to test updating the firmware and it appears to not work via a
> mini-pci to WWAN 3G USB adapter.
>
> Others have reported:
> "After Emeryth published the pinout, I also started to experiment with
> this board. I found out that you can update the firmware using the LEA-5
> firmware version 6.02 from the u-blox web site. The module also works very
> well with the patched firmware version EXT_G50_602_LEA-5H.
> bdbfccefb9dbd8395dec7adece53c1f9.bin. This version enables the output of
> raw data for use with rtklib for real-time kinematic and precision
> positioning.
>
> You can then use the standard drivers from the u-blox web site for
> Windows. They provide a virtual COM port. Please note that updating the
> firmware just worked using the physical serial port of the Mini-PCIe card,
> it did not work using the USB adapter."
>
>
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Paul
> Sent: Tuesday, August 16, 2016 2:27 AM
> To: Discussion of precise time and frequency measurement <
> time-nuts@febo.com>
> Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2
> SoC serial port for ntpd
>
> On Mon, Aug 15, 2016 at 5:35 AM, STR .  wrote:
>
> > Pardon my ignorance, I'm not sure what COM port the PPS is tied to or
> > what you mean.
>
>
> I think there's some confusion.
>
> Normally the PPS input to Linux (I'm not sure about FreeBSD) is tied to
> the DCD pin in a serial port.  The PPS code is connected to the interrupt
> from the DCD.  It can be tied to another pin (DSR or CTS I forget), a
> parallel port or a GPIO pin (a la RaspberryPi or BeagleBone).  Anything
> other than DCD normally requires a specific kernel build.  The APU2c has an
> I/O part connected via an LPC bus.  It's essentially 4 UARTS.  UART-a is
> connected to a DE-9 connector via a level shifter.  All signals are
> present.  UART-b is brought to J3 unshifted.  Even though J3 has five pins
> only transmit, receive and ground are connected.  UARTs "c" and "d" are
> brought to J17 either as 18 GPIO signals or 2x8 RS-232 signals (the latter
> requires non-standard bios code to set up the chip).  So if we imagine that
> you want to use the DCD pin on UART-c you'd configure the GPIO pins as
> serial and connect to pin 9 on J17.  Be advised that the specifics in the
> previous may be wrong so check the schematic.
>
> Now if you want to read the correct time as a sentence from the GPS you'd
> connect the Tx/Rx pins on your module to the corresponding pins on a 3V3
> serial port.  Continuing to use UART-c that would be pins 7 and 8 on J17.
>
> Now regarding jitter.  Pascal suggests that the jitter involved in using
> his take on the LPC connected super i/o part might be too high.  As noted
> someone said that was the case with the APU1.  While I wouldn't be
> surprised if that were still true with the APU2 you might find the time
> "good enough".  Trust but verify.
>
> Finally, these boxes are intended to be routers (hence the three network
> interfaces) not time-servers and unless you're irrevocably wedded to the
> miniPCIe in APU2 route there are probably better choices for time servers.
> ___
> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> and follow the instructions 

Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[STR .]

Thank you!
Your post has made my choices clear, UART-c might be it!
A previous poster said there'd be no difference in jitter using any of the 4 
COM ports and this was reassuring.
I will start studying the pinouts to confirm the pin numbers while I wait for 
the null-modem cable to arrive.

Another question, would connecting PPS, Tx/Rx to the GPIO pins on UART-c  make 
U-blox's Windows u-Center software see this as attached to a physical serial 
port?
If not, how would I present the GPS to Windows via serial?
I'd like to test updating the firmware and it appears to not work via a 
mini-pci to WWAN 3G USB adapter.

Others have reported:
"After Emeryth published the pinout, I also started to experiment with this 
board. I found out that you can update the firmware using the LEA-5 firmware 
version 6.02 from the u-blox web site. The module also works very well with the 
patched firmware version 
EXT_G50_602_LEA-5H.bdbfccefb9dbd8395dec7adece53c1f9.bin. This version enables 
the output of raw data for use with rtklib for real-time kinematic and 
precision positioning.

You can then use the standard drivers from the u-blox web site for Windows. 
They provide a virtual COM port. Please note that updating the firmware just 
worked using the physical serial port of the Mini-PCIe card, it did not work 
using the USB adapter."



-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Paul
Sent: Tuesday, August 16, 2016 2:27 AM
To: Discussion of precise time and frequency measurement 
Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
serial port for ntpd

On Mon, Aug 15, 2016 at 5:35 AM, STR .  wrote:

> Pardon my ignorance, I'm not sure what COM port the PPS is tied to or 
> what you mean.


I think there's some confusion.

Normally the PPS input to Linux (I'm not sure about FreeBSD) is tied to the DCD 
pin in a serial port.  The PPS code is connected to the interrupt from the DCD. 
 It can be tied to another pin (DSR or CTS I forget), a parallel port or a GPIO 
pin (a la RaspberryPi or BeagleBone).  Anything other than DCD normally 
requires a specific kernel build.  The APU2c has an I/O part connected via an 
LPC bus.  It's essentially 4 UARTS.  UART-a is connected to a DE-9 connector 
via a level shifter.  All signals are present.  UART-b is brought to J3 
unshifted.  Even though J3 has five pins only transmit, receive and ground are 
connected.  UARTs "c" and "d" are brought to J17 either as 18 GPIO signals or 
2x8 RS-232 signals (the latter requires non-standard bios code to set up the 
chip).  So if we imagine that you want to use the DCD pin on UART-c you'd 
configure the GPIO pins as serial and connect to pin 9 on J17.  Be advised that 
the specifics in the previous may be wrong so check the schematic.

Now if you want to read the correct time as a sentence from the GPS you'd 
connect the Tx/Rx pins on your module to the corresponding pins on a 3V3 serial 
port.  Continuing to use UART-c that would be pins 7 and 8 on J17.

Now regarding jitter.  Pascal suggests that the jitter involved in using his 
take on the LPC connected super i/o part might be too high.  As noted someone 
said that was the case with the APU1.  While I wouldn't be surprised if that 
were still true with the APU2 you might find the time "good enough".  Trust but 
verify.

Finally, these boxes are intended to be routers (hence the three network
interfaces) not time-servers and unless you're irrevocably wedded to the 
miniPCIe in APU2 route there are probably better choices for time servers.
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Paul]

On Tue, Aug 16, 2016 at 3:36 PM, Attila Kinali  wrote:

> I disagree here. With the APU and its IRQ system you get already to
> sub-us PPS time stamping (probably in the 10ns-100ns range).
>

An APU1 post said they had 50ms of jitter (as measured by Chrony) so they
assumed the PPS driver was broken on the hardware.  Pascal suggested
elsewhere that the combined LPC plus system IRQ jitter would be too much
for NTP.  While I don't believe this I'm disinclined to test it .  So I was
-- clearly too briefly -- implying that there are solutions that should be
less expensive* and known to achieve micro-second jitter.

I had no reason to suspect Pascal would overestimate the issues however
another APU1 owner** used an mPCIe serial card and an mPCIe GPS card and
got expected microsecond jitter (as measured by NTP) results.  Again this
is not quite what the OP is proposing but it's encouraging.

These are time sync. protocol results and don't speak to sub-microsecond
time-stamping in the hardware.

* which is not to say pcengine hardware is expensive.  It's not.
** https://wiki.polaire.nl/doku.php?id=versalogic_vl-mpeu-g2_ntp
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Attila Kinali]

On Mon, 15 Aug 2016 16:57:27 -0400
Paul  wrote:

> Finally, these boxes are intended to be routers (hence the three network
> interfaces) not time-servers and unless you're irrevocably wedded to the
> miniPCIe in APU2 route there are probably better choices for time servers.

I disagree here. With the APU and its IRQ system you get already to
sub-us PPS time stamping (probably in the 10ns-100ns range).
This is way than good enough for a NTP server. It should be even good
enough for an PTP system, if normal network switches are used.

The advantage of the APU is that you have a standard PC, which simplifies
the use of software considerably. Of course, with an embedded system
you can get the PPS timestamping down to <10ns precision. But at an
several times larger software complexity, which you also have to build
yourself to a large extend.

Unless time-nuts levels of precision/accuracy are required, an APU
is good enough and an easy solution. If you go for time-nuts levels,
then I would question the use of ethernet long before I question
the hardware platform.

Attila Kinali
-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Paul]

On Mon, Aug 15, 2016 at 5:35 AM, STR .  wrote:

> Pardon my ignorance, I'm not sure what COM port the PPS is tied to or what
> you mean.


I think there's some confusion.

Normally the PPS input to Linux (I'm not sure about FreeBSD) is tied to the
DCD pin in a serial port.  The PPS code is connected to the interrupt from
the DCD.  It can be tied to another pin (DSR or CTS I forget), a parallel
port or a GPIO pin (a la RaspberryPi or BeagleBone).  Anything other than
DCD normally requires a specific kernel build.  The APU2c has an I/O part
connected via an LPC bus.  It's essentially 4 UARTS.  UART-a is connected
to a DE-9 connector via a level shifter.  All signals are present.  UART-b
is brought to J3 unshifted.  Even though J3 has five pins only transmit,
receive and ground are connected.  UARTs "c" and "d" are brought to J17
either as 18 GPIO signals or 2x8 RS-232 signals (the latter requires
non-standard bios code to set up the chip).  So if we imagine that you want
to use the DCD pin on UART-c you'd configure the GPIO pins as serial and
connect to pin 9 on J17.  Be advised that the specifics in the previous may
be wrong so check the schematic.

Now if you want to read the correct time as a sentence from the GPS you'd
connect the Tx/Rx pins on your module to the corresponding pins on a 3V3
serial port.  Continuing to use UART-c that would be pins 7 and 8 on J17.

Now regarding jitter.  Pascal suggests that the jitter involved in using
his take on the LPC connected super i/o part might be too high.  As noted
someone said that was the case with the APU1.  While I wouldn't be
surprised if that were still true with the APU2 you might find the time
"good enough".  Trust but verify.

Finally, these boxes are intended to be routers (hence the three network
interfaces) not time-servers and unless you're irrevocably wedded to the
miniPCIe in APU2 route there are probably better choices for time servers.
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[STR .]

Pardon my ignorance, I'm not sure what COM port the PPS is tied to or what you 
mean.

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Albertson
Sent: Monday, August 15, 2016 2:30 AM
To: Discussion of precise time and frequency measurement 
Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
serial port for ntpd

Why not use the same COM port the PPS is tied to.  Apparently in can accept the 
3 volt serial signal.  The PPS goes to one of the control lines to create an 
interrupt and the data goes to Rx and Tx.

On Sun, Aug 14, 2016 at 9:37 AM, STR .  wrote:

> Thanks for your previous email, it shed light on the situation of 
> choosing COM ports.
>
> COM1 is required for console access so that's out.
> COM2 has headers and seemed like an obvious choice as I have no real 
> need for a 2nd serial port.
>
> I wish to power the GPS via the mini-PCI slot to avoid soldering power 
> cables along with a PPS line.
> Will there be any difference in jitter between using the COM2 header 
> or
> COM3 provided by the NCT5104D GPIO pins?
> Or will they both be identical in performance?
>
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of 
> Attila Kinali
> Sent: Sunday, August 14, 2016 5:30 PM
> To: Discussion of precise time and frequency measurement < 
> time-nuts@febo.com>
> Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to 
> APU2 SoC serial port for ntpd
>
> On Sun, 14 Aug 2016 08:29:48 +
> "STR ."  wrote:
>
> > Serial port 3 and 4 are provided via the GPIO pins connected to an
> NCT5104D I/O controller which is 5V tolerant.
> > http://datasheet.octopart.com/NCT5104D-Nuvoton-datasheet-38893851.pd
> > f I believe that's why it was suggested to avoid the 3V-5V 
> > conversion.
>
> Oops.. I missed that the other UARTs were connected to the GPIO header.
>
> If you use those, you can directly connect the LEA outputs, as the LEA 
> does use 3.3V CMOS for I/O.
>
> Attila Kinali
> --
> Malek's Law:
> Any simple idea will be worded in the most complicated way.
> ___
> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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> the instructions there.
>



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Scott Stobbe]

There should be no difference between COM2 or COM3/4, all four UARTs are
likely hard logic. GPIO is just an alternate function for the COM3/4 pins.
It will come down to what your are more comfortable with code or soldering.
The NCT5104D is a QFP and its pins are reasonably accessible using 30 AWG
or finer gauge wire.

On Sun, Aug 14, 2016 at 12:37 PM, STR .  wrote:

> Thanks for your previous email, it shed light on the situation of choosing
> COM ports.
>
> COM1 is required for console access so that's out.
> COM2 has headers and seemed like an obvious choice as I have no real need
> for a 2nd serial port.
>
> I wish to power the GPS via the mini-PCI slot to avoid soldering power
> cables along with a PPS line.
> Will there be any difference in jitter between using the COM2 header or
> COM3 provided by the NCT5104D GPIO pins?
> Or will they both be identical in performance?
>
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Attila
> Kinali
> Sent: Sunday, August 14, 2016 5:30 PM
> To: Discussion of precise time and frequency measurement <
> time-nuts@febo.com>
> Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2
> SoC serial port for ntpd
>
> On Sun, 14 Aug 2016 08:29:48 +
> "STR ."  wrote:
>
> > Serial port 3 and 4 are provided via the GPIO pins connected to an
> NCT5104D I/O controller which is 5V tolerant.
> > http://datasheet.octopart.com/NCT5104D-Nuvoton-datasheet-38893851.pdf
> > I believe that's why it was suggested to avoid the 3V-5V conversion.
>
> Oops.. I missed that the other UARTs were connected to the GPIO header.
>
> If you use those, you can directly connect the LEA outputs, as the LEA
> does use 3.3V CMOS for I/O.
>
> Attila Kinali
> --
> Malek's Law:
> Any simple idea will be worded in the most complicated way.
> ___
> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
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> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> and follow the instructions there.
>
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Paul]

On Sun, Aug 14, 2016 at 12:37 PM, STR .  wrote:
> COM2 has headers and seemed like an obvious choice as I have no real need
for a 2nd serial port.

COM2 does not have control lines.  Unless you're going to rewrite the PPS
kernel module you have to use COM1 or GPIO.  Sadly GPIO is not plug and
play. However it's not impossible.  Someone on the PCEngines forum may have
done it already.

>From the doc pages 8/9.
J3 COM2 3.3V serial port (RXD / TXD only).
...
J22 COM1 Serial port. Full handshake signals this time...


P.S.
Pascal's comment about jitter is not relevant to normal NTP.

--
Paul
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Chris Albertson]

Why not use the same COM port the PPS is tied to.  Apparently in can accept
the 3 volt serial signal.  The PPS goes to one of the control lines to
create an interrupt and the data goes to Rx and Tx.

On Sun, Aug 14, 2016 at 9:37 AM, STR .  wrote:

> Thanks for your previous email, it shed light on the situation of choosing
> COM ports.
>
> COM1 is required for console access so that's out.
> COM2 has headers and seemed like an obvious choice as I have no real need
> for a 2nd serial port.
>
> I wish to power the GPS via the mini-PCI slot to avoid soldering power
> cables along with a PPS line.
> Will there be any difference in jitter between using the COM2 header or
> COM3 provided by the NCT5104D GPIO pins?
> Or will they both be identical in performance?
>
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Attila
> Kinali
> Sent: Sunday, August 14, 2016 5:30 PM
> To: Discussion of precise time and frequency measurement <
> time-nuts@febo.com>
> Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2
> SoC serial port for ntpd
>
> On Sun, 14 Aug 2016 08:29:48 +
> "STR ."  wrote:
>
> > Serial port 3 and 4 are provided via the GPIO pins connected to an
> NCT5104D I/O controller which is 5V tolerant.
> > http://datasheet.octopart.com/NCT5104D-Nuvoton-datasheet-38893851.pdf
> > I believe that's why it was suggested to avoid the 3V-5V conversion.
>
> Oops.. I missed that the other UARTs were connected to the GPIO header.
>
> If you use those, you can directly connect the LEA outputs, as the LEA
> does use 3.3V CMOS for I/O.
>
> Attila Kinali
> --
> Malek's Law:
> Any simple idea will be worded in the most complicated way.
> ___
> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> and follow the instructions there.
>



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[STR .]

Thanks for your previous email, it shed light on the situation of choosing COM 
ports.

COM1 is required for console access so that's out.
COM2 has headers and seemed like an obvious choice as I have no real need for a 
2nd serial port.

I wish to power the GPS via the mini-PCI slot to avoid soldering power cables 
along with a PPS line.
Will there be any difference in jitter between using the COM2 header or COM3 
provided by the NCT5104D GPIO pins?
Or will they both be identical in performance?


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Attila Kinali
Sent: Sunday, August 14, 2016 5:30 PM
To: Discussion of precise time and frequency measurement 
Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
serial port for ntpd

On Sun, 14 Aug 2016 08:29:48 +
"STR ."  wrote:

> Serial port 3 and 4 are provided via the GPIO pins connected to an NCT5104D 
> I/O controller which is 5V tolerant.
> http://datasheet.octopart.com/NCT5104D-Nuvoton-datasheet-38893851.pdf
> I believe that's why it was suggested to avoid the 3V-5V conversion.

Oops.. I missed that the other UARTs were connected to the GPIO header.

If you use those, you can directly connect the LEA outputs, as the LEA does use 
3.3V CMOS for I/O.

Attila Kinali
--
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Attila Kinali]

On Sun, 14 Aug 2016 08:29:48 +
"STR ."  wrote:

> Serial port 3 and 4 are provided via the GPIO pins connected to an NCT5104D 
> I/O controller which is 5V tolerant.
> http://datasheet.octopart.com/NCT5104D-Nuvoton-datasheet-38893851.pdf
> I believe that's why it was suggested to avoid the 3V-5V conversion.

Oops.. I missed that the other UARTs were connected to the GPIO header.

If you use those, you can directly connect the LEA outputs, as the LEA
does use 3.3V CMOS for I/O.

Attila Kinali
-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Attila Kinali]

On Sun, 14 Aug 2016 02:32:13 +
"STR ."  wrote:

> I would like to install and power the GPS from the mini-PCI slot and output 
> PPS directly on to one of the serial ports on the SoC board for ntpd.
> 
> Since mini-PCI uses  3.3V and serial uses 5V I guess, I'm not sure how to 
> achieve this and am concerned I might fry the board.


It depends on where you want to connect it to. You have 3 choices:

1) COM1 after the level converter
2) COM1 before the level converter
3) COM2

Option 1) needs +/-5V, options 2) and 3) work with 3.3V.
But: both options 2) and 3) require you soldering directly
onto the APU board: for 2) you need to unsolder U37 and you will
lose your console serial port. For 3) you need to solder wires
directly onto the pins of U9 as the signals have not been broken
out onto testpoints.


For more information, see the APU schematics and the NCT5104D datasheet.

Attila Kinali
-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[STR .]

What details would you like to know?

Serial port 3 and 4 are provided via the GPIO pins connected to an NCT5104D I/O 
controller which is 5V tolerant.
http://datasheet.octopart.com/NCT5104D-Nuvoton-datasheet-38893851.pdf
I believe that's why it was suggested to avoid the 3V-5V conversion.


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Albertson
Sent: Sunday, August 14, 2016 12:01 PM
To: Discussion of precise time and frequency measurement 
Subject: Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC 
serial port for ntpd

It looks like you would have to level-convert the 3 volt PPS to connect to
one of the GPIO pins.   It is easy to make a level converter with a FET or
you can buy one for $3 from Adafruit or spark fun.As for the serial
data, that will be easy as there seems to be a 3 volt serial port.

The direct connection that was suggested might work or might not it depends on 
some details we don't know.

Seems like a good low power embedded PC.   Very much over kill for just
running NTP but I assume this will do other things too.

On Sat, Aug 13, 2016 at 7:32 PM, STR .  wrote:

> Hi,
>
>
>
> I recently bought 2 ublox PCI-5S mini-PCI GPS modules and have ordered 
> a PCengines APU2C4 board I hope to install it in.
>
> Others have found it can provide PPS output http://emerythacks.blogspot.
> in/2013/01/u-blox-pci-5s-cheap-gps-module-for-your.html
>
>
>
> This is the x-64 AMD SoC by PCengines - 
> http://www.pcengines.ch/apu2c4.htm
>
> Schematics - http://www.pcengines.ch/schema/apu2c.pdf
>
> User manual (Page 8 has a nice overview of the board) - 
> http://www.pcengines.ch/pdf/apu2.pdf
>
>
>
> I would like to install and power the GPS from the mini-PCI slot and 
> output PPS directly on to one of the serial ports on the SoC board for ntpd.
>
> Since mini-PCI uses  3.3V and serial uses 5V I guess, I'm not sure how 
> to achieve this and am concerned I might fry the board.
>
>
>
> Do I need a MAX 232 voltage converter?
>
> Can this be done using the mini-PCI slot for power?
>
>
>
> I have posted my issue on the PCengines forum and got 1 response so 
> far that suggested I connect to COM3 on the GPIO header  -
>
> http://www.pcengines.info/forums/?page=post=B4D54F22-
> 8224-4A67-9F9E-85F988A1F888=DF5ACB70-99C4-4C61-AFA6-4C0E0DB05B2A
>
> I'm not sure where exactly, these are the GPIO pins on the board 
> http://imgur.com/a/bAZLb
>
>
>
> When someone says "LPC serial IRQ and system interrupt latency will 
> add up to noticeable jitter" does that mean the jitter would be 
> equally bad from any serial port on the board or just from the 3rd serial off 
> the GPIO pins?
>
> Here, someone else claims the PPS should have less jitter in a similar 
> setup - http://pcengines.info/forums/?page=post=CD275C4D-8050-
> 408A-BD16-6F50468C74C2
>
>
>
> I'm hoping someone here could help me out with this as I'm well in 
> over my head by now.
>
>
>
>
>
>
>
> Cheers,
>
> S
>
> ___
> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
> https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow 
> the instructions there.
>



-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[Chris Albertson]

It looks like you would have to level-convert the 3 volt PPS to connect to
one of the GPIO pins.   It is easy to make a level converter with a FET or
you can buy one for $3 from Adafruit or spark fun.As for the serial
data, that will be easy as there seems to be a 3 volt serial port.

The direct connection that was suggested might work or might not it depends
on some details we don't know.

Seems like a good low power embedded PC.   Very much over kill for just
running NTP but I assume this will do other things too.

On Sat, Aug 13, 2016 at 7:32 PM, STR .  wrote:

> Hi,
>
>
>
> I recently bought 2 ublox PCI-5S mini-PCI GPS modules and have ordered a
> PCengines APU2C4 board I hope to install it in.
>
> Others have found it can provide PPS output http://emerythacks.blogspot.
> in/2013/01/u-blox-pci-5s-cheap-gps-module-for-your.html
>
>
>
> This is the x-64 AMD SoC by PCengines - http://www.pcengines.ch/apu2c4.htm
>
> Schematics - http://www.pcengines.ch/schema/apu2c.pdf
>
> User manual (Page 8 has a nice overview of the board) -
> http://www.pcengines.ch/pdf/apu2.pdf
>
>
>
> I would like to install and power the GPS from the mini-PCI slot and
> output PPS directly on to one of the serial ports on the SoC board for ntpd.
>
> Since mini-PCI uses  3.3V and serial uses 5V I guess, I'm not sure how to
> achieve this and am concerned I might fry the board.
>
>
>
> Do I need a MAX 232 voltage converter?
>
> Can this be done using the mini-PCI slot for power?
>
>
>
> I have posted my issue on the PCengines forum and got 1 response so far
> that suggested I connect to COM3 on the GPIO header  -
>
> http://www.pcengines.info/forums/?page=post=B4D54F22-
> 8224-4A67-9F9E-85F988A1F888=DF5ACB70-99C4-4C61-AFA6-4C0E0DB05B2A
>
> I'm not sure where exactly, these are the GPIO pins on the board
> http://imgur.com/a/bAZLb
>
>
>
> When someone says "LPC serial IRQ and system interrupt latency will add up
> to noticeable jitter" does that mean the jitter would be equally bad from
> any serial port on the board or just from the 3rd serial off the GPIO pins?
>
> Here, someone else claims the PPS should have less jitter in a similar
> setup - http://pcengines.info/forums/?page=post=CD275C4D-8050-
> 408A-BD16-6F50468C74C2
>
>
>
> I'm hoping someone here could help me out with this as I'm well in over my
> head by now.
>
>
>
>
>
>
>
> Cheers,
>
> S
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> and follow the instructions there.
>



-- 

Chris Albertson
Redondo Beach, California
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[time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

[STR .]

Hi,



I recently bought 2 ublox PCI-5S mini-PCI GPS modules and have ordered a 
PCengines APU2C4 board I hope to install it in.

Others have found it can provide PPS output 
http://emerythacks.blogspot.in/2013/01/u-blox-pci-5s-cheap-gps-module-for-your.html



This is the x-64 AMD SoC by PCengines - http://www.pcengines.ch/apu2c4.htm

Schematics - http://www.pcengines.ch/schema/apu2c.pdf

User manual (Page 8 has a nice overview of the board) - 
http://www.pcengines.ch/pdf/apu2.pdf



I would like to install and power the GPS from the mini-PCI slot and output PPS 
directly on to one of the serial ports on the SoC board for ntpd.

Since mini-PCI uses  3.3V and serial uses 5V I guess, I'm not sure how to 
achieve this and am concerned I might fry the board.



Do I need a MAX 232 voltage converter?

Can this be done using the mini-PCI slot for power?



I have posted my issue on the PCengines forum and got 1 response so far that 
suggested I connect to COM3 on the GPIO header  -

http://www.pcengines.info/forums/?page=post=B4D54F22-8224-4A67-9F9E-85F988A1F888=DF5ACB70-99C4-4C61-AFA6-4C0E0DB05B2A

I'm not sure where exactly, these are the GPIO pins on the board 
http://imgur.com/a/bAZLb



When someone says "LPC serial IRQ and system interrupt latency will add up to 
noticeable jitter" does that mean the jitter would be equally bad from any 
serial port on the board or just from the 3rd serial off the GPIO pins?

Here, someone else claims the PPS should have less jitter in a similar setup - 
http://pcengines.info/forums/?page=post=CD275C4D-8050-408A-BD16-6F50468C74C2



I'm hoping someone here could help me out with this as I'm well in over my head 
by now.







Cheers,

S

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