This is a programmable infrared (remote control) transmitter, which can be controlled from a PC serial port. It is capable of sending many remote control formats, including the Philips RC-5 standard. The controller will accept commands on the serial port. Settings are: 19200 bps, 8 bits, no parity, 1 stopbit, no flow control (XON/XOFF or RTS/CTS). Commands consist of hex coded bytes and must be written on the port as ASCII characters separated by space, terminated by ENTER (ASCII char 0d). You can use a terminal emulator program to test out the circuit (for example minicom on linux, NC terminal on DOS, or hyperterminal on windows), but the settings usually won't work at first, so it is recommended that you write a small program to set the parameters and send commands by pressing keys on the keyboard.
To program the controller to send a "channel +" command to an ITT 3520 video recorder, you need to send:
55 38 10 8 1 1 1 3 1 1
This command will set these parameters: T=560 usec, header pulse=16T, header gap=8T. bit0 pulse=1T, bit0 gap=1T, bit1 pulse=1T, bit1 gap=3T, tail pulse=1T
56 31 ce 01 fe
This command will send the required command bytes to the video recorder. You can see that this format contains some type of ID and a command code. Each byte is transmitted normally then with all bits reversed. You can repeat this second command more times to ensure reception. The easiest is if you find the specification of your remote. Good pages to start are: the SIRCS page and the HP48 remote control program page. If you have no success, you need to measure the signal timings yourself. If you don't have a storage oscilloscope, here is a cheap trick: connect an IR receiver module to your soundcard line input and digitize the modulation waveform of all the buttons on your remote with a sound recorder and editor program. Here is a waveform example for the ITT 3520 video recorder remote.
http://jap.hu/electronic/irtx_pic.html
