Serial comms to multiple pics

ringo · Joined: 10 Feb 2004 Posts: 8

I want to hook my pc to multiple pics on 1 pcb. I'll have a max232 chip to do teh level conversion, but my question is can I tie the tx lines from each pic together and then route them to the MAx232 chip. The pics will not be talking at teh same time, but my question is does #use rs232() function tristate the outputs when not transmitting? if not will a simple x=input(tx_pin) be good enough after packet is sent? I could put in a mux of some sort but don't have much board space left.
Thanks
Ringo

Mark · Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA

You should use RS485 for what you are doing.

BTW, it does not matter what the PIC is doing with the Tx line. What matters is what the transceiver (RS232 chip) is doing.

ringo · Joined: 10 Feb 2004 Posts: 8

485 still involves more IC's which I'm trying to stay away from. THe TX (tx from the pics point of view) lines will just be inputs into the transceiver, so it is not an issue. What I want to avoid is the contention on the lines from both pics driving thier tx lines at the same time.
Ringo

Mark · Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA

Okay, I see now that you are only using 1 RS232 transceiver. Sounds like a bad design idea to me. CCS isn't going to tristate the Tx pin. But, you can do this your self. Just enable it before you transmit and disable it after. Just make sure the data is sent out the tx shift register before you disable it.