> (2)  Somebody on the list  recently indicated that it was  easy to convert
> from RS232 to RS485, I have no problem at the PIC level but without
> purchasing an expensive RS485 Card for my PC which is  intended  to be the
> master controller in a multi-drop system I am having difficulty in enabling
> the RS485 driver from a standard PC RS232 port while transmitting  and then
> disabling the driver and still be able to listen  for a reply on the PC
port.

Not easy to go from RS-232 to RS-485, since one is going from point to point
to a multidrop environment. We did it on a 16C57 with an interesting amount of
circular buffers, multitasking and network processing. (One has to treat the
485 connection as a network with some sort of protocol to keep terminals from
killing each other's messages. I like CSMA/CD, but there are other token
passing, etc. schemes that also work.)

The RS-232 connection into the PIC becomes just a drop on the net with an
address so it can read / write to / from any other point. Obviously speed
matching becomes a real problem unless the same speed and / or tiny packets
are used.

Tom