Timing

The bit length is approximately 1.8ms. The code is repeated every 114ms. To improve noise rejection, the pulses are modulated at 36kHz. This can be seen in the RC5 IR Receiver figure below. The easiest way to receive these pulses is to use an integrated IR-receiver/demodulator like the Siemens SFH 506-36. This is a 3-pin device that receives the infra-red burst and gives out the demodulated bit stream at the output pin. Note that the data is inverted compared to the transmitted data (i.e., the data is idle high). The output of the demodulator device is connected to PD2 on the AVR device. The decoded instructions in this case will be output on PORTB, but the chosen port is easily reconfigurable.

Figure 1. RC5 Receiver