Hi,
slightly offtopic, but in the same vein as the original question.

When using RS485 ( i.e. 2 wire halfduplex connection ) as opposed to=20
RS422 (4 wire fullduplex connection) we all know (or should know) that
one needs to supply some kind of RTS signal that controls the
transmitter.
The 'problem' with this in regards to the pic is that the TX irq is
triggered
when an byte is transfered to the tx shift register and not when it's
empty.
So hence we cannot use the tx irq for controlling the 'rts' signal
directly.

Now, the other day, I had an idea , is it possible to actually send an
dummy
byte after the last byte ( 0x00 or 0xFF ) and use that as an 'timer' for
the
rts control ?. I.e. when you are sending the last byte you set an flag,=20
at the next tx irq you know that the byte is transfered to the=20
tx shift register and are beeing sent out, now send the dummy byte and
wait until next tx irq at which time we disable the 'rts' signal.

Would this work ? if not why ?

And I'm curious what will happen with the 'dummy' byte, is it possible
that
is will start beeing shifted out before we can disable the transmitter ?

An idea I had but I'm not sure I thought it trough fully, any comments ?

/Tony=20

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu