> > 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.
Yes it is probably a long SPI cable but it is possible to slow down speed. The Master In Slave Out MISO signal is a problem because there must be enough time for this signal to return before the next SCK clock flank. Within circuit board SPI provide cheap and fast communication. I have need for more than one instance of the same circuit and planned to use several single instance cards, here it might also work. > 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. If you have two SPI ports and do not use the MISO signal return path speed will increase. It might also be possible to skip the chip select signal and instead detect absence of clock signal as packet delimiter but it might be harder to implement than anticipated at least on some devices. UART might be good if it is possible to get the correct bit rate at high speed, this might be a problem if there i n counts per bit. It is usually also more limited then it come to speed. Regards 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
