On Monday 29 May 2017 18:57:00 Bertho Stultiens wrote: > On 05/30/2017 12:39 AM, Gene Heskett wrote: > >>> I may have a fix to the SPI problem. There seems to be a problem > >>> in clock-setting, which me apparently have been seeing. The > >>> attached patch is very simple and works correct and so all the > >>> time. > >> > >> And some images how it looks now :-) > > > > That does look better. What sort of probes are you useing on that > > tek sampler? > > The probes that came with the scope: > Tektronix TPP0200 (300V CAT II) > 1:10 probe, 10 MOhm, <12 pF > > It is ringing a lot because of long (jumper-) wires attached to the > pi's extension-header. But I don't care for testing purposes. > > >> I did see some more optimizations that can be applied. The > >> transfers can almost be halved in time if the code does write/read > >> operations from/to the SPI registers in a smarter way. If speed > >> becomes an issue, send me a request for fixing it ;-) > > > > That sounds like a heck of a deal, and s/b committed. Better > > transfer speeds=lower ferrors in linuxcnc. > > Yes, that is a big deal. The question would then be if the FPGA can > keep up on the larger request packets. That I cannot tell. > > At the moment, the code sends 4 bytes and then reads 4 bytes. The code > actually stalls until those bytes are sent/read before the next 4 > bytes are processed. The BCM2835 has a 16-word fifo, which could be > used asynchronously to speed up transfers. > > > Now if Sebastian would get us a buildbot built for armhf again, > > hint, hint. :) 3-30 pf trimmer caps s/b be here around the 5th, and > > if what I found works, I can get on with the build in a day or so. > > I'm building an SD card right now that should contain my entire setup. > I'll put it on the net as soon as I get it ready so you can test it > (with new kernel and patched lcnc).
Sounds good. From this end I can report that it appears to be working when a cap marked 10, that measures 13 pf or so, has been pasted on the bottom of the pi, between one of the grounds at pin 25, and the spi0clk at pin 23. A quick check to see if z jogs looks good on the scope. I also found the calibrate signal on this fawncy scope, while more than adequate to adjust the probes comp trimmers, actually has a very leasurely rise and fall time in the 500ns area. BBLB crap obviously, so one cannot assess the true hf response using its own test signal. I've got a function generator that can beat that like a white mouthed mule! A 1950's model kay megasweep would be handy as he!! about now. Thanks Bertho, a lot. 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
