X Infrared Remote Control

Posted on Feb 7, 2014

The ELM622 by ELM Electronics is a preprogrammed PIC which converts commands from a Sony infrared remote control into a serial data stream. An IR receiver using a ELM622 requires no kernel modifications. This project shows how to build a Linux IR receiver based on the ELM622 and how to use the receiver to control an X application such as xmms. The

X Infrared Remote Control
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software presented in this article converts the IR codes from the ELM622 into X-Window keycodes and sends the keycodes to any X application you specify. The IR codes could as easily be converted into a string of keycodes for more complex commands from a single IR remote keypress. The X IR Remote Control (xirrc) could be used as a second, specialized keyboard. The output of the ELM622 is an asynchronous serial character for every keypress on the remote. The serial data is sent at 9600 baud with 8, N, 1 framing. A very nice data sheet is available in PDF format. The ELM622 has eight pins including power, ground, IR data in, and serial data out. There is also an input for CTS, an output for RTS, a reset output, and an output to drive an LED to indicate received data. The following block diagram of the ELM622 is taken from the data sheet. The five volt supply consists of diode D2, capacitor C1, and the Zener diode D1. Diode D1 is a 1N4733 5. 1 volt Zener available from Radio Shack as Catalog Number 276-565. C1 is a 25 volt 0. 1 micro-farad capacitor. Diodes D2, D3, and D4 are all 1N4002 or equivalent. The TTL to RS-232 converter is the op-amp, resistors R1 and R2, and the +/- 10 volt power supply formed by diodes D3 and D4. Note that we use the Tx data from the computer as the negative supply. The resistors bias the non-inverting input to about 2. 2 volts. As the inverting input swings above or below 2. 2 volts the output...

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