This is pretty long...

I have two boards with 16c63 parts connected to LTC485 485 drivers.  Pin C5
is used to enable the driver.  The receiver is enabled at all times.

To test the hardware I wrote two simple programs, one for receive, and one
for transmit.  The transmit code turns on the 485 driver and sends
alternating + and - with a 500 ms period.  The receive code disables the
driver, and listens for incoming characters.  When it receives a +, it
turns on an led, when it received a -, it turns off an led.

It didn't work, so I did the following:

1) I hooked up the RX data pin on the receive side to a PC via a MAX233.
It show that at the PIC, the + and - characters are being received.

2) I pulled the 485 driver and connected the PIC directly to a PC via the
MAX233 and sent + and - characters from the keyboard.  It worked fine.

3) I then put the 485 driver back in.  I did leave the MAX233 connected to
the transmit side so I could send out some info for debug purposes.  Based
on that info, when connected to the other PIC, the rx PIC receives two
characters, +- or -+ depending on when I hook it up, and then waits for
ever for another character.

Conclusion:

When connect to the PC the rx side works.
When connected to another PIC the rx side does not.

Any ideas?

Thanks,

Kevin Russell
kevin.russell@null.net