IR wavelenghts



know anybody, what is the main wavelenght of HP's IR ports?
And where I can find some about the HP calc's communication methods?

Thank you!


While the IR wavelenght (from an optical point of view) is not critical at all, the frequency and coding of the pulses certainly is. The first IR models used an HP proprietary format, sometimes refered to as "RedEye"; some newer units as the LX100/200 PC Palmtops used the standarized IRDA (which is similar to an IR asynchronous serial port).

An article about the RedEye protocol appeared in the HPJournal in 1987, I think it was mentioned here before many times, and certainly is part of the CD set from the Museum. In the Archives forum you will find many references, including an interesting article (around 2000)from Steve (Australia) who managed to receive the pulse stream from an HP calculator on a PC, by means of a phototransistor connected to the input of the PC sound card.


Most IR LEDs from that time period emitted at 750-900 nm.


You don't mention which models, but I guess that the IR I/O would be
similar for most models, excepting the 49g+ using IrDA I/O. For
"Serial IR" I/O, see
(plain text) or (PDF).
For "Red-Eye" output (used for printing), see




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