The RedRat2 from Chris Dodge at
http://www.redrat.co.uk/index.html is a small device that enables your computer to act as a remote control. It attaches to most types of computer via the serial port, so your computer can learn IR remote control commands and play them back under software control.
There are many different hardware solutions for sending and receiving IR from a computer. The RedRat has several advantages that made me go with this one:
- The RedRat uses a microcontroller in the RedRat for the delicate timing involved. Other units rely on the desktop computer to send ones and zeros at exactly the right time, which requires careful programming and plenty of free CPU cycles. A computer need only send a string of about 50 characters to the RedRat to have it send a signal.
- The RedRat uses a serial connection instead of a parallel port. This is better because
- The cable can be longer
- Most types of computers have a serial port, while only PC's have parallel ports
- Now that most PC's have PS/2 mouse ports, they usually have a free serial port. If you have a printer, usually you will not have a free parallel port.
- The signal output modulation frequency is set using a variable resistor. Different remote controls can use different modulation frequencies, so an
improved performance is obtained by allowing the output modulation frequency to be set via software on a signal to signal basis.
- Embedded in the string that goes between the RedRat and the computer is a checksum, so you know if the signal was transmitted correctly.
- The microcontroller knows a few other commands. For instance, if you send it a "[I]", it sends back the version of firmware and version of hardware. This can be used to verify proper operation. Sending it a "[B]", it will blink the visible red LED inside the unit. This can be used to acknowledge commands have been executed.
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