Simple IrDA Transmitter

Communication over the IrDA port uses a relatively complex protocol but its possible to send a single character using just a few components. In many cases this will be sufficient to control a Palmtop. This circuit generates a single pulse of IR light that is interpreted by the Palmtop as a data byte with the value 255. The circuit could hardly be simpler, a 1 µF capacitor is charged via the 27 k? resistor and when the switch is pressed this charge will flow through the diode to generate an IR light pulse.