"connect" one pin to another

[colinbrenton]

Hello,

I am using a 18F6527. One one UART I have a PC, on the the other I want to connect two other devices.

Is there a way I can feed UART2 (TX and RX) to two general purpose IO pins, and connect the two devices to be served to four other IO pins, then "map" between them, selecting one device or the other?

I suppose an ISR may be needed, to monitor for change-of state on the pins, and pass the changes through the system, but a "virtual switch" would be easier...

These RS232 links will be 0-5v, rather than +/-15, so that shouldn't cause any problems

Any suggestions?

Thanks in advance,


Colin

[FvM]

Internal multiplexing of UART function to different chip pins isn't possible with standard PICs. You have to use external multiplexers.

[colinbrenton]

Hi FmV,

Thanks for your repply, looks like a hardware block is needed then.

Cheers,

Colin

[asmboy]

the usual way to share out 2 RS-232 ports is to connect
the TX pin to BOTH TX side pins of say a max232.
ONE for EACH of the two ports.

the RX is a different matter - you need to take the TWO RX outs from your pair of MAX232's and then
feed EACH of those into a 74HC08 or equiv AND gate input.

Now the OUTPUT of the HC08 goes to your RX pin on the pic
NB:
NONE of this will save your bacon if BOTH of the bonded RS-232 external devices talk simultaneously to you

the result will be garbage

FYI