I don't know if the latest HPs use the same protocol as the HP82240B
printer.
This is a 24 odd column standalone IR interfaced printer used with
the older IR capable calculators.

If they do, then the advice on this subject posted here seems to be
wrong. Perhaps the later units use a simpler protocol. If not, I can
help with the HP82240B protocol.HP can provide a very comprehensive
brochure on the protocol.

We connected to these directly for a vehicle based project but I also
tried using infra reed and it worked very successfully over  arrange
of 1 to 2 feet. More would have been easy. The serial protocol sends
bits which have a number of pulses of high or low depending on
whether a 1 or a 0. The pattern is not intuitive and is not straight
Manchester AFAIR. To convert to IR I simply gated the output of a 32
KHz oscillator using a 74C14 as the oscillator. HP say that the bits
must be synchronised with the 32 KHz signal but in my tests this did
not seem to be the case. In the limited tests that I did I got 100%
copy with asynchronous 32KHz oscillator. Also HPs specs for the
maximum and minimum number of 32 KHz pulses per bit suggest that I
was not violating this requirement.

I can probably turn up more details on the protocol if required -
this will not be the case if the other advice given is in fact
correct. Our system used an Atmel 2051 but I am (probably) not able
to release the code. PIC implementation should be easy. I looked at
an an IR version using a 6MHz ST6 but it was just too slow :-). PIC
should be easily fast enough to generate the 32KHz modulated pulses
directly.



regards




            Russell McMahon

From: Don Holtz <daholtz@AXIONET.COM>

>Does anyone have info on the serial protocol that HP uses to
implement
>their infra-red serial interface - for calculators and palmtops.
>
>I have an HP-48S, and several HP palmtops that I would like to use
to talk to
>a PIC.
>
>Any ideas?
>
>Cheers,
>Don
>