PIC12F629 based IR decoder

Posted on Feb 4, 2014

The IR Widget captures the infrared signals used by remote controls. It is able to determine the carrier frequency and demodulate the carrier in the digital or analog domain. The captured information can be used to reproduce or recognize the signal. The hardware is designed to be as simple and low cost as possible. A PIC12F629 was used for the pro

PIC12F629 based IR decoder
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totype, but almost any PIC that uses the 12 or 14 bit instruction set could be used. The usual approach to low cost IR capture typically consists of an IR detector or demodulator module connected to a serial or parallel port. This can work quite well when the CPU is dedicated to servicing the port. It does not work very well within a preemptive multitasking operating system. The OS is constantly servicing hardware interrupts even when the system is idle, so the IR capture is constantly interrupted. CPU usage is high when polling is used. Using the hardware interrupt capability of the port can greatly reduce CPU load, but interrupt latency may cause inaccurate results. Parallel and serial ports are becoming less common, and USB adapters do not work for these simple circuits. The IR Widget solves these problems by using a microcontroller to do precise timing and send the data to the PC using ordinary asynchronous serial transmission. This allows the OS to service the serial port with it ’s normal drivers and allows the use of USB to serial converters. The circuit is powered from the serial port and the PIC directly drive the serial rx data line. An infrared detector module is used to allow the PIC to see every infrared pulse at close range. This allows for greatest detail and accuracy. An infrared demodulator module can also be used to allow for long range reception with less detail. Infrared remotes typically use a carrier...

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