Oh, and somethings else I forgot to mention...

DMX packets start with a BREAK signal, which is a low on the TXD pin of between 92-176us.

For the transmitter I found it easier to generate the DMX BREAK signal using an extra IO pin.
Put a 1-5K series resistor between the pic TX output and the 485 transceiver txd input pins, and tie the IO pin to that junction.
Code:
PIX TX out ---/\/\/\---------->RS485 TX IN
IO pin     ____________|
Normally, set the IO pin as an input so it's floating. When you want to generate the BREAK signal set it to output low
for between 92us-176us and then make it an input again. You can also generate the BREAK timing by fidgeting around with the uart baudrate
and transmitting a single 00 byte, but I found this to be a lot simpler.