Gianfranco (The MOD Team): ... > The physical interface of the Control Chain devices is an RS-485 > full-duplex serial line running at 1Mbit/sec. Currently up to eight > devices can be daisy chained and by use of the RJ-45 cable we also > power the devices ( 1 pair for input,1 for output and 1 for power supply). ...
How are you handling "collisions" and idle bus (rs485 does not specify that kind of things) ? Idle bus can be taken care of with a resistor devider (as described in e.g. [1]), but that solution draws power when the bus is idle. Why not a "active" kind of termination by connecting "A" to +2, 3.3, or 5V and "B" to GND (or vice versa), both throught 60 Ohm resistors ? "Collision" handling can be avoided by using a one master and letting the other nodes to be slaves, and polling the slaves. Or one can use something similar to J1708 [2] and CAN by driving the device enable pin instead of the transmit pin and let the bus "float" (by setting the output driver to hi-z) up/down to the "recessive" state by a "idle bus"/failstate circuit. You have to have some software to detect any collisions then. I drafted some thoughts in [3], but havn't implemented it "yet". Ideas ? Regards, /Karl Hammar [1] http://www.ti.com/lit/an/slyt324/slyt324.pdf [2] http://www.ti.com/lit/an/snla038b/snla038b.pdf [3] http://turkos.aspodata.se/git/openhw/serial_bus/Readme ----------------------------------------------------------------------- Aspö Data Lilla Aspö 148 S-742 94 Östhammar Sweden +46 173 140 57 _______________________________________________ Linux-audio-dev mailing list [email protected] http://lists.linuxaudio.org/listinfo/linux-audio-dev
