> > > > > > 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.
If distance is long enough drivers are required it might be time to switch for Ethernet based or CAN. 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
