Hi All,
I am putting several PICs on 2-wire RS485 bus.  They all need to 
communicate with a laptop computer so I am exploring different options 
for connecting the computer to the bus.

1. A PIC using its UART on the 485 bus and bit-banging 232 to the 
computer (or the other way around).  I'm not terribly happy about the 
bit-banging, especially at higher data rates, although I probably won't 
be operating it very fast.
2. Two PICs, one with UART on 232 and one with UART on 485, interlinked 
over SPI.  Seems a bit clumsy.
3. Direct conversion.  A MAX232 connected to a MAX3158 or similar RS485 
transceiver.  Only tough bit is turning on the "driver enable" pins on 
the transceiver.  Could the RTS line from the 232 connection be used for 
this if the PC is set to Hardware flow control?  What I mean is, if I 
set Hyperterminal to RTS/CTS handshaking will it automatically turn on 
the RTS line for the duration of each byte? If not perhaps I could 
achieve the same goal manually by writing software that turns on the RTS 
line, sends a whole packet of data then turns it off again.
Alternatively I saw this page: 
http://www.edn.com/article/CA74434.html?1=1 which uses a 555 timer as a 
monostable, triggered by the start bit in the RS232 byte.  However this 
means picking a fairly narrow range of baud rates, and means that the 
other nodes on the 485 bus need to wait a certain amount of time before 
transmitting.

Related question: is there an easy/"clever" way of enabling/disabling 
the RS485 drivers on a PIC communicating on a 485 bus when using the 
internal UART? I was thinking of enabling them when writing to TXREG and 
then disabling them in the TX interrupt.

Thanks very much for your time.

Henry Hallam
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