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This project contains a port of the well-known C++ library DecodeIR to the Arduino platform. It requires somewhat more that 100kB flash space, and 2kB of RAM space. It will not run on the smaller boards, like the Uno.


The original library was written by Jon Fine, who put it into the public domain. It has been extended by may others, in particular Graham Dixon ("mathdon") and Dave Reed ("3FG"). It is "maintained" in the JP1 forum.

This project can be considered as a fork of the 2.45 tag from the official sources at SourceForge. My version presently contains only the files relevant for the Arduino port. The other files (Java JNI interface, autoconfig files, Maven pom) are found in the original repository.

The official documentation is contained here as the file DecodeIR.html.


This project is a straight-forward port of DecodeIR 2.45. It is intended to be functionally equivalent. The main changes necessary was to use the C99 portable types (like uint32_t etc.) instead of the, per definition, non-portable types like int and char. Somewhat simplified, most ints have been replaced by int32_t, unsigned ints by uint32_t, and chars (used as numbers) by uint8_t.

Also the dependence of std::set has been removed. (This was the only dependence of the standard C++ library.)


The library proper does not depend on any other Arduino library. However, the examples do depend on Infrared4Arduino, IRremote, and/or LiquidCrystal_I2C.

Version 2.45.1 and 2.45.2 inadvertently depended on Infrared4Arduino for compilation.


The main file DecodeIR[h,cpp] has a single public entry point, DecodeIR(...), documented in DecodeIR.cpp (line 5412ff in the current version). A slightly more user friendly method is presented by the wrapper file `decodePrintIr.[h,cpp]. Note that the two "lengths" are in "number of bursts", not in number of durations. (The number of bursts is half the number of durations). The example files is probably the easiest way to learn how to use the library, using the wrapper.


The file main.cpp is a small main routine, that can be used on Unix-like system to create a command line program that will decode signal in the Pronto Hex format. This can be useful e.g. for testing. It is not intended to run on the Arduino. To compile, use the supplied Makefile.

Questions, maintenence, contributions

This project is intended as a port of the current version of DecodeIR. Issues with the port should be directed to me, e.g. as issue. Questions, extensions regarding protocols etc should be directed to the JP1 forum.

Here is a thread in the JP1-Forum discussing the current project.

The official DecodeIR is not being developed any more. I intend this project to be a port of the official one, and for that reason, improvements and extensions are not really solicited. PR in this direction will likely be rejected.

But, of course, feel free to develop your own fork; this is Open Source!


DISCONTINUED: An Arduino port of DecodeIR version 2.45.








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