> > > > > RS422 is balanced and opt isolated at the Mesa card end so you > > > > > likely have better noise resistance then with SPI. > > > > > > > > rs485 is the single ended cousin. Could a atom board keep up with > > > > that with a pci-e rs422 card in it? That does have a bit of an > > > > attraction, particularly from the noise safety dept. Silly Q: can > > > > the pi do rs422 over its gpio? > > > > > > Hook a RS485/RS422 transceiver to a Pi's serial TXD & RXD, and > > > terminate each end of the twisted pair cable in 120 ohms, then it's > > > done. All the chip does is TTL/CMOS to differential Tx & Rx. > > > > What is the maximum bit rate of the Pi's serial TXD & RXD? The 7i90 > > can accept RS422 up to 10M bits/second. Can the Pi take advantage > > that? Certainly an Intel PC could, > > > I don't see why not. The spi runs with a 32 megahertz clock, thru 4 gpio > pins. Its a half-duplex protocol.
SPI use separate clock signal while and one data channel in each direction although but it is of course no problem to only use one. RS422 do not have a separate clock signal and instead synchonize to the flanks of the signal, most probably to the start of the first flank. RS244 might be able to receive data sent from SPI level is correct and start/stop is inserted but not the opposite. > I agree. The only problem with this board is that its rs485 only. > Unbalanced IOW. So theres goes some of the noise margin. And its data > rate must be pretty slow, its slew rated but not in any usefull way. Ideally it should be isolated and shielded differential twisted pair but if length of cable is short and no noise there is no need. It is common to use high speed SPI communication on circuit board single ended without drive but here distance is short and usually there is a ground plane all the way close the signal. ------------------------------------------------------------------------------ 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
