avr-redeye

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This is a implementation of the HP RedEye infrared protocol used on HP 82240A printers as used for printing from their great graphing calculators.

This implementation currently works on a Arduino Duemilanove prototyping board which has a AVR ATMega328P running at 16 MHz and connected via a integrated USB to serial bridge (ft232), but you can easily port it to any other AVR with the two standard 8- and 16-bit timers.

AVR Resources:

This code uses Timer/Counter 0 in Fast-PWM-Mode to create
the 32kHz IR carrier, the IR-LED is connected to OC0B/PD5.

Timer/Counter 1 runs at about a 7th the rate and does the
bit-timing, turning off T/C0 (and hence the LED) as needed by the
protocol.

In principle, you could still use T/C1 for PWM, T/C2 is not
used at all.

To use this code as is:

Connect a IR LED with the anode connected to arduino digital output 6 and the cathode connected to ground, with a 100 Ohm resistor or so in series.

The actual implmenentation is in avr-redeye.h and .c, there are only two relevant functions:

 avr_redeye_init() sets up the timers

 avr_redeye_put(c) puts a character "c" in the buffer to be sent
 to the printer

There's a little demo script test_redeye.py (written in python, using the pyserial module to access the serial port) as a short example.

Read the included .pdf for the exact specification from HP.

LICENSE:

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

https://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html