IR Communications for Atmel Mega644/1284 microcontrollers.
Infrared (IR) can be used for line-of-sight communications over low to moderate range. IR is nice because of the lack of interference (except for sun and compact fluroscent lights) and freedom from FCC regulation. The web site http://tthheessiiss.wordpress.com/2009/08/05/dirt-cheap-wireless/ (Jacob Sikker Remin, 2009) shows how to use a IR remote control receiver and IR LED to send ASCII serial data in a simple, but unreliable, fashion with no error control, packetizing, or other overhead. The transmitter drive uses a clever method to modulate and invert the serial output from the USART transmitter. The circuit is shown below.
Infrared Communications for Atmel Mega644/1284 microcontrollers – [Link]