madler@tybalt.caltech.edu (Mark Adler) (01/14/90)
Well, after messing around with the resistor and getting better, but not good enough results, it dawned on me how to get around the run-together- bits problem in software. I had not previously considered using the information available about the length of the pulse. The melded bits only occur for adjacent half-bit times with pulses, so all I have to do is decode the run-together-bits for what they are, using the length of the pulse to figure out how many there are. I did that. I now have a program that can download data from an HP-28S (and presumably any other HP with an IR LED) using an unmodified Radio Shack GP1U52X Infrared Receiver (catalog number 276-137), available for a mere $3.49 (plus tax). I decided to make the program (written in Turbo C 2.0) shareware, and I am charging a modest $5 for it. I will send a separate mail item containing the source to comp.sys.handhelds. So for less than $10 and little bit of wiring, you can read data from your HP into your PC. The details are in the source code. Have fun. Mark Adler madler@hamlet.caltech.edu The opinions expressed here are not in fact mine, but rather belong to a small worm that lives on the fourth planet out from Betelgeuse.