I have a project that stores both calibration info and data logging
information on it.  The product will be firmly fixed inside the cab of
18 wheelers.  The information will only be accessed once per month.  The
options are:

1) Run a 200 foot extention cord out to the unit once per month.  No, I
can not leave the cord laying out accoss the middle of the parking lot
for hundreds of trucks to run over it.

2) RF Link:  Plausible but too expensive when talking about 20-100
trucks per fleet.

3) Have the customer buy a laptop and run it out to the truck whenever
they need to and plug it in.  Customer said "NO!".  They would prefer a
small handheld unit that will capture the information and can then
download it to their PC.

4) Build my own PDA and use whatever IR communication protocals I want.

5) Buy someone else's PDA (like a Palm Pilot, Handspring, etc.) and just
program it.

The last option sounds the best but have no idea how to interface to
it.  What is the spectrum frequency of the IR emittor and detector
(IrDA)? What is the baud rate on the transmission? When I want to send
the letter "A" to the PDA, what does the waveform look like?

Unconfirmed info that I have found so far is that it uses 9600 baud and
it sends a packet of 64 bytes at a time.

Writing the program for the PDA is the easy thing.  What do I do on the
PIC side to make it compatible??