Multiple Data on to USART RX pin

[Squibcakes]

Hi Geeks,

I want to know the RIGHT way to join (parallel) four seperate serial data lines to the single USART RX pin on a PIC.

Only one serial line will be enabled at a time (coming from RS422 line receiver chips).

The easiest solution is to just S/C the four signal lines but is this correct?

Can I use schottky diodes on each serial line or should I just use a 4 input OR gate instead?

Is there a better method that I haven't thought of?

Thanks.
Squib

[BobK]

Hi Squibcakes,

I have 20 PIC serial lines (software, not USART) coming into 1 software serial pin. All of the lines have a 1K resistor in series with the main receiver line. I used a 100K pull up on the receiver input. I have a separate "busy" line that all "talkers" check before sending data to the receiver and to prevent crashes each one has to wait 10ms more than the previous one before it sends. All 20 lines are set as inputs until they have to send. When they are finished, I reset the pin to an input again. Its been working great since May 2005. Steven Collins helped me out with the problem.

Hope this helps!

BobK

[Squibcakes]

Bob thanks for your reply, yes it helps!.

I think my project is reverse to yours, ie rather than 20 PICs connected to a single PC input, I have multiple PC's connected to a single PIC. (Actually 4x RS-422 inputs via line receivers connected to the PIC USART).

Anyway,

I have a new problem which I will post in a different thread.

Thanks
J