Application Notes

AN-1042 Remote Control IR Reciever/Decoder

This design is a configurable remote control infrared receiver and decoder. It also performs address and command comparison, and provides a matching true indicator. It is designed compliant with the NEC protocol, and can be configured for any 8-bit address and remote control command. The NEC protocol uses “pulse distance” encoding of the bits. Each pulse is a 560µs long pulse burst with 38kHz carrier (about 21 periods). A logic "1" takes 2.25ms to transmit, while a logic "0" is only half of that, being 1.125ms. The typical carrier duty-cycle is 1/4 or 1/3 for optimum range and power considerations. Figure 1 shows a typical pulse train of the NEC protocol. LSB is transmitted first. A message is started by a 9ms AGC burst, which is used to set the gain of some IR receivers that might require it. This AGC burst is then followed by a 4.5ms space, which is then followed by the Address and Command

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Tags

Sensor, Remote Control, Infared Receiver, Decoder, NEC Protocol, AGC burst, TSOP4838, S2P


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