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 <ghesk...@shentel.net>
> > Reply-To: "Enhanced Machine Controller (EMC)"
> > <emc-users@lists.sourceforge.net>
> > To: emc-users@lists.sourceforge.net
> > 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.
Thanks for any further enlightenment you can share Peter
> Peter Wallace
> Mesa Electronics
>
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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>
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