The purpose of this project is to build a device that can capture the Infrared (IR) signal transmitted by all types of remote controls. It can capture IR codification signal at the modulation frequency level. This device not only simply captures IR signal, it also can decode this IR signal. Telling us what codification is used and what code was transmitted.
The project uses phototransistor Q1 (OP800A) to captures IR signal. The carrier frequency of the IR signal is maximum 120 kHz (satellite receivers). That’s why the type of phototransistor isn’t so important. But it must be an IR phototransistor or a phototransistor with work wavelength between IR and visible. Transistor Q2 is a buffer element, it is in switching mode. At the pin TB5in (number 29) of M16C/62P microcontroller, the signal from Q1 will be inverted. All the others elements of scheme are for the interface with user (switches S1-S4, LED, LCD module, potentiometer R11).
Although hardware design is simple, the firmware is very complicated. It takes a big amount of memory and of CPU time. The program is written in C language. The program of this device is divided into 4 files (without counting the default included files). This files contains logically divided function, each file contains only functions that do a specific work.