On Tue, 16 May 2017, Gene Heskett wrote:
> Date: Tue, 16 May 2017 15:40:41 -0400
> From: Gene Heskett <[email protected]>
> Reply-To: "Enhanced Machine Controller (EMC)"
> <[email protected]>
> To: [email protected]
> Subject: Re: [Emc-users] switching to a slower spi driver to see if it works,
>
> On Tuesday 16 May 2017 14:33:29 Peter C. Wallace wrote:
>
>> On Tue, 16 May 2017, Gene Heskett wrote:
>>> Date: Tue, 16 May 2017 13:22:59 -0400
>>> From: Gene Heskett <[email protected]>
>>> Reply-To: "Enhanced Machine Controller (EMC)"
>>> <[email protected]>
>>> To: [email protected]
>>> Subject: Re: [Emc-users] switching to a slower spi driver to see if
>>> it works,
>>>
>>> On Monday 15 May 2017 09:58:04 Gene Heskett wrote:
>>>
>>> I may have found it!!!
>>>
>>> Hooking up my scope, I discovered that the original query to get the
>>> board to ID itself, IS NOT MADE AT THE SAME CLOCK SPEED IT ACTUALLY
>>> OPERATES AT. THE INITIAL QUERY IS BEING MADE AT 50 MHz!
>>>
>>> I hung a scope probe on the clock, which due to its loading, changed
>>> the shape of the waveform and made it work. Its now running at 32
>>> MHz, but I had captured the initial failure, and that was clocked at
>>> 50MHz.
>>>
>>> Now, I'll go remove my scope probe and see if it fails.
>>>
>>> Better yet, without the probe it fails, with the probe on the pi end
>>> of the 82 ohm terminating resistor I used in my home made adapter,
>>> it works 5 out of 5 times. Move the probe to the other end of that
>>> resistor and the failure rate is 5 out of 5 times. I took some pix
>>> of the single trace capture of this startup card query. Quite a bit
>>> of the voltage swing the pi is generating is being used up in the
>>> resistor, at least half a volt.
>>>
>>> Pix on my web page at
>>> <http://geneslinuxbox.net:6309/gene/lathe-stf/Sheldon_lathe-pix/Upst
>>> ream-sclk.jpg> and
>>> <http://geneslinuxbox.net:6309/gene/lathe-stf/Sheldon_lathe-pix/Down
>>> stream-sclk.JPG>
>>>
>>> I note that if it succeeds, which it seems to do with my probe
>>> furnishing some initial loading, it then slows to 32MHz for the
>>> clock rate.
>>>
>>> And, when its hooked up with the OSHPark adapter and its 86.7 ohm
>>> resistors, there is not enough signal to tickle the 7i90 into
>>> responding at all.
>>>
>>> I'll go hook it up with one of those & try it again.
>>>
>>> Cheers, Gene Heskett
>>> --
>>> "There are four boxes to be used in defense of liberty:
>>> soap, ballot, jury, and ammo. Please use in that order."
>>> -Ed Howdershelt (Author)
>>> Genes Web page <http://geneslinuxbox.net:6309/gene>
>>>
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>>
>> 50 MHz will work if everything is terminated correctly and if the RSPI
>> timing is correct. (It may require using a SPI late data sample option
>> if the RSPI hardware has that option)
>>
>> Correct series termination of RSPI outputs (130 Ohm total for 0.050"
>> flat cable) depends on the output impedance of the RSPI outputs so
>> there's no guarantee that the added 87 ohms is correct (this may also
>> depend on RSPI output drive strength settings if such things exist on
>> the RSPI)
>>
>>
> All of which is UNK ATM, Peter, as I haven't bitten the bullet and
> downloaded the src for the whole thing. One thing is surprising though,
> all the modules and such for master-sim carry a Dec 22, 2016 build date.
> I am tempted to change my apt/sources.list.d/linuxcnc file and point it
> at master-rt. The newest hm2_rpspi I have won't even load, but its
> around 2500 bytes bigger, dated May 2, 2017.
>
> So I changed it, made no difference, apt says everything is uptodate?
> apt list shows:
> linuxcnc-doc-en/now 1:2.8.0~pre1.2771.gdc2ff49 all [installed,local]
> linuxcnc-uspace/now 1:2.8.0~pre1.2771.gdc2ff49 armhf [installed,local]
> linuxcnc-uspace-dev/now 1:2.8.0~pre1.2771.gdc2ff49 armhf
> [installed,local]
>
> ??????????
>
> Remove and re-install? Or does somebody need the apply some brogan
> maintenance to the armhf leg of the buildbot?
>
> Silly Q, Peter, do I actually need a longer cable? I have NDI how long a
> cable was used when developing the OSHPark adapter and its choice of 88
> ohm resistors. Looking at the waveforms, I get the impression 68 ohms
> might be a better match. I could throw a 10" cable together in 20
> minutes or less. I had figured the shorter the better so what I have is
> only 6 or 7". 4" didn't work, I tried that already with the Park adapter
> boards.
I doubt that longer is better, but a 68 or 50 Ohm clock series
termination resistor may be better. No idea what the RSPI output
impedances are but you could get a fair guess by resistive loading the bare
clock output and seeing what drop you get
are
>
> Thanks for any further enlightenment you can share Peter
>
>> Peter Wallace
>> Mesa Electronics
>>
>> (\__/)
>> (='.'=) This is Bunny. Copy and paste bunny into your
>> (")_(") signature to help him gain world domination.
>>
>>
>> ----------------------------------------------------------------------
>> -------- Check out the vibrant tech community on one of the world's
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>> _______________________________________________
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>
>
> Cheers, Gene Heskett
> --
> "There are four boxes to be used in defense of liberty:
> soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> Genes Web page <http://geneslinuxbox.net:6309/gene>
>
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> _______________________________________________
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> https://lists.sourceforge.net/lists/listinfo/emc-users
>
Peter Wallace
Mesa Electronics
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(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination.
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