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IRremote Arduino Library

Available as Arduino library "IRremote"

Version 3.0.0 - work in progress

License: MIT Commits since latest Installation instructions Join the chat at LibraryBuild

This library enables you to send and receive using infra-red signals on an Arduino.

Tutorials and more information will be made available on the official homepage.


Click on the LibraryManager badge above to see the instructions.

Supported IR Protocols

Denon, JVC, LG, NEC, Panasonic / Kaseikyo, RC5, RC6, Samsung, Sharp, Sony, (Pronto), BoseWave, Lego, Whynter, MagiQuest.
Protocols can be switched off and on by changing the lines in IRremote.h:

#define SEND_<PROTOCOL_NAME>    1


This is a quite old but maybe useful wiki for this library.

Converting your program to the 3.x version

  • Now there is an IRreceiver and IRsender object like the well known Arduino Serial object.
  • Just remove the line IRrecv IrReceiver(IR_RECEIVE_PIN); and/or IRsend IrSender; in your program, and replace all occurences of IRrecv. or irrecv. with IrReceiver.
  • Also remove the line decode_results results or similar, since the decoded values are now in IrReceiver.decodedIRData and not in results any more.
  • Like for the Serial object, call IrReceiver.begin(IR_RECEIVE_PIN, ENABLE_LED_FEEDBACK); or IrReceiver.begin(IR_RECEIVE_PIN, DISABLE_LED_FEEDBACK); instead of the IrReceiver.enableIRIn(); or irrecv.enableIRIn(); in setup().
  • Old decode(decode_results *aResults) function is replaced by simple decode(). So if you have a statement if(irrecv.decode(&results)) replace it with if (IrReceiver.decode()).
  • results.value moved to IrReceiver.decodedIRData.decodedRawData.
  • results.decode_type moved to IrReceiver.decodedIRData.decodedRawData.
  • Overflow, Repeat and other flags are now in IrReceiver.receivedIRData.flags.
  • Seldomly used: results.rawbuf and results.rawlen moved to IrReceiver.decodedIRData.rawDataPtr->rawbuf and IrReceiver.decodedIRData.rawDataPtr->rawlen.

If you discover more changes, which should be documented, please send me a mail to


  • IR does not work right when I use Neopixels (aka WS2811/WS2812/WS2812B)
    Whether you use the Adafruit Neopixel lib, or FastLED, interrupts get disabled on many lower end CPUs like the basic Arduinos for longer than 50 µs. In turn, this stops the IR interrupt handler from running when it needs to. There are some solutions to this on some processors, see this page from Marc MERLIN
  • The default IR timer on AVR's is timer 2. Since the Arduino Tone library as well as analogWrite() for pin 3 and pin 11 requires timer 2, this functionality cannot be used simultaneously. You can use tone() but after the tone has stopped, you must call IrReceiver.enableIRIn() to restore the timer settings for receive.
    If you can live with the NEC protocol, you can try the MinimalReceiver example, it requires no timer.
  • You can use multiple IR receiver by just connecting the output pins of several IR receivers together. The IR receivers use an NPN transistor as output device with just a 30k resistor to VCC. This is almost "open collector" and allows connecting of several output pins to one Arduino input pin.

Minimal version

For applications only requiring NEC protocol, there is a receiver which has very small codesize and does NOT require any timer. See the MinimalReceiver and IRDispatcherDemo example how to use it.

Handling unknown Protocols


This library was never designed to handle long codes like the ones used by air conditioners. See Recording long Infrared Remote control signals with Arduino.
The main reason is, that it was designed to fit inside MCUs with relatively low levels of resources and was intended to work as a library together with other applications which also require some resources of the MCU to operate.


If you do not know which protocol your IR transmitter uses, you have several choices.

  • Use the IRreceiveDump example to dump out the IR timing. You can then reproduce/send this timing with the IRsendRawDemo example. For long codes with more than 48 bits like from air conditioners, you can change the length of the input buffer in IRremote.h.
  • The IRMP AllProtocol example prints the protocol and data for one of the 40 supported protocols. The same library can be used to send this codes.
  • If you have a bigger Arduino board at hand (> 100 kByte program space) you can try the IRremoteDecode example of the Arduino library DecodeIR.
  • Use IrScrutinizer. It can automatically generate a send sketch for your protocol by exporting as "Arduino Raw". It supports IRremote, the old IRLib and Infrared4Arduino.
  • To increase strength of sent output signal you can increase the current through the send diode, or use 2 diodes in series, since one IR diode requires only 1.5 volt. Changing IR_SEND_DUTY_CYCLE to 50 increases the signal current by 40%.

Compile options / macros for this library

To customize the library to different requirements, there are some compile options / macros available.
Modify it by commenting them out or in, or change the values if applicable. Or define the macro with the -D compiler option for global compile (the latter is not possible with the Arduino IDE, so consider using Sloeber.

Name File Default value Description
IR_INPUT_IS_ACTIVE_HIGH IRremoteint.h disabled Enable it if you use a RF receiver, which has an active HIGH output signal.
DEBUG IRremote.h disabled Enables lots of lovely debug output.
USE_NEC_STANDARD IRremote.h disabled Use LSB first, address/code schema for encoding.
USE_NO_SEND_PWM IRremote.h disabled Use no carrier PWM, just simulate an active low receiver signal.
USE_SOFT_SEND_PWM IRremote.h disabled Use carrier PWM generation in software, instead of hardware PWM.
PULSE_CORRECTION_MICROS IRremote.h 3 If USE_SOFT_SEND_PWM, this amount is subtracted from the on-time of the pulses.
USE_SPIN_WAIT IRremote.h disabled If USE_SOFT_SEND_PWM, use spin wait instead of delayMicros().
SUPPORT_SEND_EXOTIC_PROTOCOLS IRremote.h enabled If activated, BOSEWAVE and LEGO_PF are supported in the write method. Costs around 500 bytes program space.
RAW_BUFFER_LENGTH IRremoteint.h 101 Buffer size of raw input buffer. Must be odd!
IR_SEND_DUTY_CYCLE IRremoteBoardDefs.h 30 Duty cycle of IR send signal.
MICROS_PER_TICK IRremoteBoardDefs.h 50 Resolution of the raw input buffer data.
USE_CUSTOM_DELAY irSend.cpp disabled Use old custom_delay_usec() function for mark and space delays.
- - - -
IR_INPUT_PIN TinyIRReceiver.h 2 The pin number for TinyIRReceiver IR input, which gets compiled in.
IR_FEEDBACK_LED_PIN TinyIRReceiver.h LED_BUILTIN The pin number for TinyIRReceiver feedback LED, which gets compiled in.
DO_NOT_USE_FEEDBACK_LED TinyIRReceiver.h disabled Enable it to disable the feedback LED function.

Modifying compile options with Arduino IDE

First use Sketch > Show Sketch Folder (Ctrl+K).
If you did not yet stored the example as your own sketch, then you are instantly in the right library folder.
Otherwise you have to navigate to the parallel libraries folder and select the library you want to access.
In both cases the library files itself are located in the src directory.

Modifying compile options with Sloeber IDE

If you are using Sloeber as your IDE, you can easily define global symbols with Properties > Arduino > CompileOptions.
Sloeber settings

Other IR libraries

Here you find a short comparison matrix of 4 popular Arduino IR libraries.
Here you find an ESP8266/ESP32 version of IRremote with an impressive list of supported protocols.

Supported Boards

  • Arduino Uno / Mega / Leonardo / Duemilanove / Diecimila / LilyPad / Mini / Fio / Nano etc.
  • Teensy 1.0 / 1.0++ / 2.0 / 2++ / 3.0 / 3.1 / Teensy-LC; Credits: @PaulStoffregen (Teensy Team)
  • Sanguino
  • ATmega8, 48, 88, 168, 328
  • ATmega8535, 16, 32, 164, 324, 644, 1284,
  • ATmega64, 128
  • ATmega4809 (Nano every)
  • ATtiny84, 85
  • SAMD21 (receive only)
  • ESP32
  • ESP8266 is supported in a fork based on an old codebase. It works well given that perfectly timed sub millisecond interrupts are different on that chip.
  • Sparkfun Pro Micro

We are open to suggestions for adding support to new boards, however we highly recommend you contact your supplier first and ask them to provide support from their side.

Hardware specifications

The timer and the pin usage can be adjusted in IRremoteBoardDefs.h

Board/CPU IR-Send (PWM) Pin Timers
ATtiny84 6 1
ATtiny85 > 1 MHz 1, 4 0, 1
ATmega8 9 1
ATmega48, ATmega88, ATmega168, ATmega328 3, 9 1, 2
ATmega1284 13, 14, 6 1, 2, 3
ATmega164, ATmega324, ATmega644 13, 14 1, 2
ATmega8535 ATmega16, ATmega32 13 1
ATmega64, ATmega128, ATmega1281, ATmega2561 13 1
ATmega8515, ATmega162 13 1
ATmega1280, ATmega2560 5, 6, 9, 11, 46 1, 2, 3, 4, 5
ATmega4809 5, 6, 9, 11, 46 TCB0
Leonardo (Atmega32u4) 5, 9, 13 1, 3, 4_HS
Zero (SAMD) *, 9 TC3
ESP32 4, all pins 1
Sparkfun Pro Micro 5, 9 1, 3
Teensy 1.0 17 1
Teensy 2.0 9, 10, 14 1, 3, 4_HS
Teensy++ 1.0 / 2.0 1, 16, 25 1, 2, 3
Teensy 3.0 / 3.1 5 CMT
Teensy-LC 16 TPM1

Adding new protocols

To add a new protocol is quite straightforward. Best is too look at the existing protocols to find a similar one and modify it.
As a rule of thumb, it is easier to work with a description of the protocol rather than trying to entirely reverse-engineer the protocol. Please include a link to the description in the header, if you found one.
The durations you receive are likely to be longer for marks and shorter for spaces than the protocol suggests, but this depends on the receiver circuit in use. Most protocols use multiples of one time-unit for marks and spaces like e.g. NEC. It's easy to be off-by-one with the last bit, since the last space is not recorded by IRremote.

Try to make use of the template functions decodePulseDistanceData() and sendPulseDistanceData(). If your protocol supports address and code fields, try to reflect this in your api like it is done in sendNEC(uint16_t aAddress, uint8_t aCommand, uint8_t aNumberOfRepeats, bool aIsRepeat) and decodeNEC().


To integrate your protocol, you need to extend the two functions decode() and getProtocolString() in IRreceice.cpp, add macros and function declarations for sending and receiving and extend the enum decode_type_t in IRremote.h.
And at least it would be wonderful if you can provide an example how to use the new protocol. A detailed description can be found in the ir_Template.cpp file.

Revision History

Please see

API documentation

See API reference in wiki.

To generate the API documentation, Doxygen, as well as Graphviz should be installed. (Note that on Windows, it may be necessary to add the Graphviz binary directory (something like C:\Program Files\Graphviz2.38\bin) to the PATH variable manually.) With Doxygen and Graphviz installed, issue the command doxygen from the command line in the main project directory, which will generate the API documentation in HTML format. The just generated api-doc/index.html can now be opened in a browser.

Why do we use 33% duty cycle

We do it according to the statement in the Vishay datasheet:

  • Carrier duty cycle 50 %, peak current of emitter IF = 200 mA, the resulting transmission distance is 25 m.
  • Carrier duty cycle 10 %, peak current of emitter IF = 800 mA, the resulting transmission distance is 29 m. - Factor 1.16 The reason is, that it is not the pure energy of the fundamental which is responsible for the receiver to detect a signal. Due to automatic gain control and other bias effects high intensity and lower energy (duty cycle) of the 38 kHz pulse counts more than high low intensity and higher energy.

BTW, the best way to increase the IR power is to use 2 or 3 IR diodes in series. One diode requires 1.1 to 1.5 volt so you can supply 3 diodes with a 5 volt output.
To keep the current, you must reduce the resistor by (5 - 1.3) / (5 - 2.6) = 1.5 e.g. from 150 ohm to 100 ohm for 25 mA and 2 diodes with 1.3 volt and a 5 volt supply.
For 3 diodes it requires factor 2.5 e.g. from 150 ohm to 60 ohm.


If you want to contribute to this project:

  • Report bugs and errors
  • Ask for enhancements
  • Create issues and pull requests
  • Tell other people about this library
  • Contribute new protocols

Check here for some guidelines.


Check here


Email: Please only email me if it is more appropriate than creating an Issue / PR. I will not respond to requests for adding support for particular boards, unless of course you are the creator of the board and would like to cooperate on the project. I will also ignore any emails asking me to tell you how to implement your ideas. However, if you have a private inquiry that you would only apply to you and you would prefer it to be via email, by all means.


Up to the version 2.7.0 the License is GPLv2. From the version 2.8.0 the license is the MIT license.


Initially coded 2009 Ken Shirriff Copyright (c) 2016 Rafi Khan Copyright (c) 2020 Armin Joachimsmeyer