On Thursday 14 September 2017 11:47:22 Nicklas Karlsson wrote: > On Thu, 14 Sep 2017 04:03:30 -0400 > > Gene Heskett <[email protected]> wrote: > > On Wednesday 13 September 2017 12:50:15 Nicklas Karlsson wrote: > > > > > No SPI over long cable. For long cable RS422 will work, there > > > > > is a tradeoff between cable length and speed. > > > > > > > > Poor wording on my part. I had, once the terminations are > > > > sorted, visions of a 3 to 4 foot cable, defined as a long SPI > > > > cable. > > > > > > > > Right now, terms are not well characterized on either end and it > > > > takes some loading trickery to make a 6 inch cable work. Bertho > > > > and I spent some time optimizing it to get 30.5 megabit one way, > > > > and 25 megabit the other direction. And its now working well to > > > > a Mesa 7i90 with a 1" cable. > > > > > > Ethernet shielded twisted pair four pairs like this: sck+gnd, > > > miso+gnd, mosi+gnd, chip select + gnd. Or flat cable with a gnd > > > cable between each of them. Or of course Ethernet if available. > > > > No, the tcp is too slow, much latency. > > For TCP resend function to make sense there must be enough time to > resend packet. > > > However, the above scheme, made into ready-made hardware and a > > matching rj45 socket signal assignment on those mesa cards that can > > support spi, like the 7i90, ... > > Ethercat chips are available with SPI interface and I concluded then > distance is short enough and data is sent between it might be a good > choice to skip the Ethercat chips but I might be wrong. > I'd be for that skip myself, if we had real line drivers in the pi's gpio. The pi's pin drivers are just barely up to the task, and too fragile electrically for true long term survival if the noise or edge ringing exceeds 4 volts. Ditto the i/o pins on the 7i90 and its ilk for that matter.
> Nicklas Karlsson > > ---------------------------------------------------------------------- >-------- 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 > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
