On Tuesday 16 May 2017 13:22:59 Gene Heskett wrote: > 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/Upstre >am-sclk.jpg> and > <http://geneslinuxbox.net:6309/gene/lathe-stf/Sheldon_lathe-pix/Downst >ream-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. > It actually is responding, but the data is trash.
With an OSHPark board adapter, I had to clip onto the back legs of the 26 pin socket on the 7i90. The clock is there, looking pretty close to what I observed on the other end of the cable, but its still trash. Houston, we do indeed have a problem, and it looks as if its a timeing problem between the clock, and the command data coming out of the pi, fixed by the 3 or 4 ns delay in the clock that hanging my scope probe on it is causing. Where can I get the src for hm2_rpspi? And who is the author? There is also some spi related stuff in /boot/config.txt: dtparam=spi=on dtoverlay=spi0-2cs dtoverlay=spi1-1cs,cs0_pin=16,cs0_spidev=disabled but, if commented out, no video drive at all on a reboot. Anybody actually know WTH it does? > I'll go hook it up with one of those & try it again. 100% failure, but there is data flowing. If I can find a low cap trimmer cap, and add it to the 40 pin side of the adapter, it might work in place of the probe. But I've been out of those critters for decades. Picture me in the basement, frantically looking for such critters. > Cheers, Gene Heskett 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 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
