Read the little write up at the Mesa site about cable length. They claim ribbon cable is the worst and to only use it for very short runs, 2 or 3 feet at most. They suggest using "real" parallel cables made with twisted pairs and shielding for longer runs. Using one of their fancy IEEE cables you can go up to 25 or 30 feet, half that with a normal round cable and half that again with ribbon cable.
For over 30 feet use some kind of differential signaling or fiber. There is nothing inherently bad about ribbon cable. It is more about how it is driven. It works well as a 50 ohm transition line if you terminate it at each end. The old SCSI disk drives did that. But there is an upper limit on how fast you can push data down a parallel cable. This is why all the really fast computer interfaces are now serial Your problem might be because you are doing to much at once. Can you get a one axis stepper motor to run slowly using GPIO and no FPGA card? Does that work reliably through multiple upgrades and config changes or is it fragile? Or even before that, can you install and update Linux and compile kernels and instal new drivers and run a web browsers and email and do upgrades and such reliably before using RPi3 as a machine controller. On Sat, Dec 24, 2016 at 4:20 AM, Gene Heskett <ghesk...@shentel.net> wrote: > Greetings folks; > > This is a heck of a thing to throw out on Christmas Eve. > > I am about burned out on trying to make the raspi 3b work. > > I saw it work once, for about 2 days, then an update blew it up by > replacing the rt kernel, and it has not worked since. In the sd cards > I've made since, probably 8 or more, following the recipe given, the > halrun;halc md loadrt hostmot2;loadrt hm2_rpspi test procedure works > perfectly. But linuxcnc refuses to load that hm2_rpspi driver. > > Mr. Martinjack built me an image and sent me the link to it. No gui, so > testing would have to be done over an ssh -Y login. He, I believe went > to quite some effort to do that, and I assume that it worked on his > raspi-3b. But when I wrote it to a zeroed 32Gb card, expanded the > filesystem on the first boot, then configured the networking in static > mode, making it immutable as I went so whatever raspian uses in place of > network-mangler can't tear it down on the next boot, the result can't do > the halrun test. > ------------------------------------------- > pi@raspberrypi:~ $ halrun > halcmd: loadrt hostmot2 > Note: Using POSIX realtime > hm2: loading Mesa HostMot2 driver version 0.15 > halcmd: loadrt hm2_rpspi > Unknown board: HOST???? > hm2_rpspi: rtapi_app_main: Operation not permitted (-1) > <stdin>:2: waitpid failed /usr/bin/rtapi_app hm2_rpspi > <stdin>:2: /usr/bin/rtapi_app exited without becoming ready > <stdin>:2: insmod for hm2_rpspi failed, returned -1 > --------------------------------------------- > which is the same failure I get when trying to start linuxcnc on one of > my builds. > > And this is the 2nd pi-3b I've put in. > > Does my use of a 32GB card have anything to do with this? > Does my use of the full jessie install instead of the jessie-lite have > anything to do with this? I can try that once. > > If that fails, I'll quit beating my head with a hammer and reset this > 7i90 to an epp interface and go back to an x86 computer to drive it, but > that brings up the next $64K question. The big old Dell I have to drive > it with isn't swarf proof by any means, and it will take at least 6 or > even 8 feet of ribbon cable to get it far enough away from the swarf to > be safe from flying chips. Can I use a ribbon cable that long with good > results? The man page says it could be a problem but doesn't say how > long is too long. And I've no clue if the parport on this old Dell can > be made epp-1.9 compliant. TBD I guess. > > Thanks everybody. And have a Merry Christmas. > > 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> > > ------------------------------------------------------------ > ------------------ > Developer Access Program for Intel Xeon Phi Processors > Access to Intel Xeon Phi processor-based developer platforms. > With one year of Intel Parallel Studio XE. > Training and support from Colfax. > Order your platform today.http://sdm.link/intel > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California ------------------------------------------------------------------------------ Developer Access Program for Intel Xeon Phi Processors Access to Intel Xeon Phi processor-based developer platforms. With one year of Intel Parallel Studio XE. Training and support from Colfax. Order your platform today.http://sdm.link/intel _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
