IR detectors are little microchips with a photocell that are tuned to listen to infrared light. They are almost always used for remote control detection – every TV and DVD player has one of these in the front to listen for the IR signal from the clicker. In this guide we will explain how IR sensors work, how to pull IR codes out of a remote control, and show you how to wire them up to a microcontroller.
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In the Linux kernel there is code that can decode a wide range of IR protocols. It works by running several state machines simultaneously. The code is small and can be easily ported to a microcontroller.
A timer input pin is commonly used to record the signals. Set it to interrupt on each state change and then read the pulse length from the timer register. Feed this timing info into the kernel’s state machines and you get decoded protocols out.
The kernel then passes these decoded events up through the input system. Higher layers turn them into key pressed events.