Greetings all; I could use some advice since this raspi-7i90 uses a com protocol, spi, that is relatively new, and I believe that is where a noise problem might lie.
I got it back to running the right rt kernel yesterday, and I am waiting on another psu & driver for the x axis. But I did get z moving. Nowhere near optimized though. That's being moved by the motor and psu I took off the mill because it was too slow. But I am being plagued by joint following errors, both axis's, when its not moving. There is not any connections yet to the x motor pins on the 7i90. This armhf setup has no PID's, so I've yet to locate where this error is generated. My hookup for the spi is currently some of those rip off the next wire and plug it in, and each is a piss-poor connector, very poor spring pressure unless I first take a tiny punch and bend the contact tab inward so it will even stay on the header pin. I've seen some mention of 80 ohm series damping resistors, but this initial hookup is straight thru, and a bit shy of 200mm long. At the speed of this interface, it really should be treated as a transmission line, but its not a very good one when its all done with loose wires. I got some of the 10 pair female connector blocks from digi-key yesterday, and the gold flashed female pins, and the crimping tool came in Tuesday, so I think the first thing I'll do today, is cut those junk connectors of these jumpers, and make it back up using these good connectors. That will shorten each wire something under an inch. It also gives me a chance to put some damping resistors in the signal lines, possibly cutting down on the ringing and the data errors that I'm convinced is the source of the joint errors being reported when there is not any motion. So my question is, are 100 ohm R's, which I have in bulk, too much? The one mention was of 80 ohm chip R's on the OHPark adaptor board I assume, which puts them right on the r-pi's header, but when the door of this box is closed, I don't have room for any additional stickup above the r-pi, but the interface on the 7i90 faces straight out, so putting them there, on the other, 7i90 end, is quite easily done. I'm also aware this is new ground, so what have the explorers here found is the best solution for an spi driven setup? Did you use loose jumpers, or did you use a ribbon cable, arranged to put a grounded wire between the signal wires? I have around 80 feet of 26 wire ribbon cable, so thats not a problem. The pin pattern on the r-pi is easily covered by one, or a piece of one of these header blocks I have now. Using ribbon cable makes it a lot easier to think of it as a transmission line, but how best to terminate it for least vswr? So lets talk. Thanks everybody. 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/xeonphi _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
