[](https://github.com/Arduino-IRremote/Arduino-IRremote/commits/master)
[](https://stand-with-ukraine.pp.ua)
* [How to convert old MSB first 32 bit IR data codes to new LSB first 32 bit IR data codes](https://github.com/Arduino-IRremote/Arduino-IRremote#how-to-convert-old-msb-first-32-bit-ir-data-codes-to-new-lsb-first-32-bit-ir-data-codes)
- [Errors with using the 3.x versions for old tutorials](https://github.com/Arduino-IRremote/Arduino-IRremote#errors-with-using-the-3x-versions-for-old-tutorials)
- [Why *.hpp instead of *.cpp](https://github.com/Arduino-IRremote/Arduino-IRremote#why-hpp-instead-of-cpp)
- [Using the new *.hpp files](https://github.com/Arduino-IRremote/Arduino-IRremote#using-the-new-hpp-files)
* [How to deal with protocols not supported by IRremote](https://github.com/Arduino-IRremote/Arduino-IRremote#how-to-deal-with-protocols-not-supported-by-irremote)
- [Examples for this library](https://github.com/Arduino-IRremote/Arduino-IRremote#examples-for-this-library)
* [Incompatibilities to other libraries and Arduino commands like tone() and analogWrite()](https://github.com/Arduino-IRremote/Arduino-IRremote#incompatibilities-to-other-libraries-and-arduino-commands-like-tone-and-analogwrite)
* [Hardware-PWM signal generation for sending](https://github.com/Arduino-IRremote/Arduino-IRremote#hardware-pwm-signal-generation-for-sending)
* [Why do we use 30% duty cycle for sending](https://github.com/Arduino-IRremote/Arduino-IRremote#why-do-we-use-30-duty-cycle-for-sending)
- [Quick comparison of 5 Arduino IR receiving libraries](https://github.com/Arduino-IRremote/Arduino-IRremote#quick-comparison-of-5-arduino-ir-receiving-libraries)
Protocols can be switched off and on by defining macros before the line `#include <IRremote.hpp>` like [here](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/master/examples/SimpleReceiver/SimpleReceiver.ino#L33):
- Supports **Universal Distance protocol**, which covers a lot of previous unknown protocols.
- Compatible with **tone()** library, see [ReceiveDemo](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/21b5747a58e9d47c9e3f1beb056d58c875a92b47/examples/ReceiveDemo/ReceiveDemo.ino#L159-L169).
- Simultaneous sending and receiving. See the [SendAndReceive](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/master/examples/SendAndReceive/SendAndReceive.ino#L167-L170) example.
- Allows for the generation of non PWM signal to just **simulate an active low receiver signal** for direct connect to existent receiving devices without using IR.
- Easy protocol configuration, **directly in your [source code](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/master/examples/SimpleReceiver/SimpleReceiver.ino#L33-L57)**.<br/>
Reduces memory footprint and decreases decoding time.
- Contains a [very small NEC only decoder](https://github.com/Arduino-IRremote/Arduino-IRremote#minimal-nec-receiver), which **does not require any timer resource**.
[-> Feature comparison of 5 Arduino IR libraries](https://github.com/Arduino-IRremote/Arduino-IRremote#quick-comparison-of-5-arduino-ir-receiving-libraries).
Starting with the 3.1 version, **the generation of PWM for sending is done by software**, thus saving the hardware timer and **enabling arbitrary output pins for sending**.<br/>
If you use an (old) Arduino core that does not use the `-flto` flag for compile, you can activate the line `#define SUPPRESS_ERROR_MESSAGE_FOR_BEGIN` in IRRemote.h, if you get false error messages regarding begin() during compilation.
- Just remove the line `IRrecv IrReceiver(IR_RECEIVE_PIN);` and/or `IRsend IrSender;` in your program, and replace all occurrences of `IRrecv.` or `irrecv.` with `IrReceiver` and replace all `IRsend` or `irsend` with `IrSender`.
- Like for the Serial object, call [`IrReceiver.begin(IR_RECEIVE_PIN, ENABLE_LED_FEEDBACK)`](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/master/examples/ReceiveDemo/ReceiveDemo.ino#L106)
or `IrReceiver.begin(IR_RECEIVE_PIN, DISABLE_LED_FEEDBACK)` instead of the `IrReceiver.enableIRIn()` or `irrecv.enableIRIn()` in setup().<br/>
For sending, call `IrSender.begin(IR_SEND_PIN, ENABLE_LED_FEEDBACK);` or `IrSender.begin(IR_SEND_PIN, DISABLE_LED_FEEDBACK);` 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())`.
- The decoded result is now in in `IrReceiver.decodedIRData` and not in `results` any more, therefore replace any occurrences of `results.value` and `results.decode_type` (and similar) to
`IrReceiver.decodedIRData.decodedRawData` and `IrReceiver.decodedIRData.protocol`.
- Overflow, Repeat and other flags are now in [`IrReceiver.receivedIRData.flags`](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/master/src/IRremoteInt.h#L164-L187).
- Seldom used: `results.rawbuf` and `results.rawlen` must be replaced by `IrReceiver.decodedIRData.rawDataPtr->rawbuf` and `IrReceiver.decodedIRData.rawDataPtr->rawlen`.
For the new decoders for **NEC, Panasonic, Sony, Samsung and JVC**, the result `IrReceiver.decodedIRData.decodedRawData` is now **LSB-first**, as the definition of these protocols suggests!<br/>
To convert one into the other, you must reverse the byte/nibble positions and then reverse all bit positions of each byte/nibble or write it as one binary string and reverse/mirror it.<br/><br/>
# Errors with using the 3.x versions for old tutorials
If you suffer from errors with old tutorial code which includes `IRremote.h` instead of `IRremote.hpp`, just try to rollback to [version 2.4.0](https://github.com/Arduino-IRremote/Arduino-IRremote/releases/tag/v2.4.0).<br/>
Most likely your code will run and you will not miss the new features...
**Every \*.cpp file is compiled separately** by a call of the compiler exclusively for this cpp file. These calls are managed by the IDE / make system.
IDE's like [Sloeber](https://github.com/ArminJo/ServoEasing#modifying-compile-options--macros-with-sloeber-ide) or [PlatformIO](https://github.com/ArminJo/ServoEasing#modifying-compile-options--macros-with-platformio) support this by allowing to specify a set of options per project.
uint16_t extra; // Used by MagiQuest and for Kaseikyo unknown vendor ID. Ticks used for decoding Distance protocol.
uint16_t numberOfBits; // Number of bits received for data (address + command + parity) - to determine protocol length if different length are possible.
uint8_t flags; // See IRDATA_FLAGS_* definitions above
uint32_t decodedRawData; // Up to 32 bit decoded raw data, used for sendRaw functions.
The content of the `IrReceiver.decodedIRData.flags` is described [here](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/master/src/IRremoteInt.h#L128-L140).
For applications only requiring NEC protocol, there is a receiver which has very **small code size of 500 bytes and does NOT require any timer**.
Check out the [MinimalReceiver](https://github.com/Arduino-IRremote/Arduino-IRremote#minimalreceiver) and [IRDispatcherDemo](https://github.com/Arduino-IRremote/Arduino-IRremote#irdispatcherdemo) examples.
IR will not work right when you use **Neopixels** (aka WS2811/WS2812/WS2812B) or other libraries blocking interrupts for a longer time (> 50 <20>s).<br/>
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 <20>s.
In turn, this stops the IR interrupt handler from running when it needs to.<br/>
You can try to wait for the IR receiver to be idle before you send the Neopixel data with `if (IrReceiver.isIdle()) { strip.show();}`. This prevents at least breaking a running IR transmission and -depending of the update rate of the Neopixel- may work quite well.<br/>
There are some other solutions to this on more powerful processors,
This is often due to resource conflicts with the other library. Please see [below](https://github.com/Arduino-IRremote/Arduino-IRremote#timer-and-pin-usage).
## Multiple IR receiver
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.
## Increase strength of sent output signal
To **increase strength of sent output signal** you can increase the current through the send diode, and/or use 2 diodes in series,
For receiving, the **minimal CPU frequency is 4 MHz**, since the 50 <20>s timer ISR takes around 12 <20>s on a 16 MHz ATmega.<br/>
For sending, the **default software generated PWM has problems on AVR running with 8 MHz**. The PWM frequency is around 30 instead of 38 kHz and RC6 is not reliable. You can switch to timer PWM generation by `#define SEND_PWM_BY_TIMER`.
For air conditioners [see this fork](https://github.com/crankyoldgit/IRremoteESP8266) which supports an impressive set of protocols and a lot of air conditioners and the blog entry:
["Recording long Infrared Remote control signals with Arduino"](https://www.analysir.com/blog/2014/03/19/air-conditioners-problems-recording-long-infrared-remote-control-signals-arduino).<br/>
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 get something like this: `PULSE_DISTANCE: HeaderMarkMicros=8900 HeaderSpaceMicros=4450 MarkMicros=550 OneSpaceMicros=1700 ZeroSpaceMicros=600 NumberOfBits=56 0x43D8613C 0x3BC3BC`,
then you have a code consisting of **56 bits**, which is probably from an air conditioner remote.
You can send it with calling sendPulseDistanceWidthData() twice, once for the first 32 bit and next for the remaining 24 bits.<br/>
**The PulseDistance or PulseWidth decoders just decode a timing steam to a bit stream**.
They can not put any semantics like address, command or checksum on this bitstream, since it is no known protocol.
But the bitstream is way more readable, than a timing stream. This bitstream is read **LSB first by default**.
If this does not suit you for further research, you can change it [here](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/master/src/ir_DistanceProtocol.hpp#L48).
If you see something like `Protocol=UNKNOWN Hash=0x13BD886C 35 bits received` as output of e.g. the ReceiveDemo example, you either have a problem with decoding a protocol, or an unsupported protocol.
- If you have an **odd number of bits** received, it is likely, that your receiver circuit has problems. Maybe because the IR signal is too weak.
- If you see timings like `+ 600,- 600 + 550,- 150 + 200,- 100 + 750,- 550` then one 450 <20>s space was split into two 150 and 100 <20>s spaces with a spike / error signal of 200 <20>s between. Maybe because of a defective receiver or a weak signal in conjunction with another light emitting source nearby.
- If you see timings like `+ 500,- 550 + 450,- 550 + 500,- 500 + 500,-1550`, then marks are generally shorter than spaces and therefore `MARK_EXCESS_MICROS` (specified in your ino file) should be **negative** to compensate for this at decoding.
- If you see `Protocol=UNKNOWN Hash=0x0 1 bits received` it may be that the space after the initial mark is longer than [`RECORD_GAP_MICROS`](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/master/src/IRremote.h#L124).
This was observed for some LG air conditioner protocols. Try again with a line e.g. `#define RECORD_GAP_MICROS 12000` before the line `#include <IRremote.hpp>` in your ino file.
For **long codes** with more than 48 bits like from air conditioners, you can **change the length of the input buffer** in [IRremote.h](src/IRremoteInt.h#L36).
- The [IRMP AllProtocol example](https://github.com/IRMP-org/IRMP#allprotocol-example) prints the protocol and data for one of the **40 supported protocols**.
[IRremoteDecode example](https://github.com/bengtmartensson/Arduino-DecodeIR/blob/master/examples/IRremoteDecode/IRremoteDecode.ino) of the Arduino library [DecodeIR](https://github.com/bengtmartensson/Arduino-DecodeIR).
- Use [IrScrutinizer](http://www.harctoolbox.org/IrScrutinizer.html).
It can automatically generate a send sketch for your protocol by exporting as "Arduino Raw". It supports IRremote,
the old [IRLib](https://github.com/cyborg5/IRLib) and [Infrared4Arduino](https://github.com/bengtmartensson/Infrared4Arduino).
In order to fit the examples to the 8K flash of ATtiny85 and ATtiny88, the [Arduino library ATtinySerialOut](https://github.com/ArminJo/ATtinySerialOut) is required for this CPU's.
Receives all protocols and **generates a beep with the Arduino tone() function** on each packet received. By connecting pin 5 to ground, you can see the raw values for each packet. **Example how to use IRremote and tone() together**.
Receives all protocols and dumps the received signal in different flavors. Since the printing takes so much time, repeat signals may be skipped or interpreted as UNKNOWN.
Serves as a IR **remote macro expander**. Receives Samsung32 protocol and on receiving a specified input frame, it sends multiple Samsung32 frames with appropriate delays in between.
This serves as a **Netflix-key emulation** for my old Samsung H5273 TV.
Example for sending LG air conditioner IR codes controlled by Serial input.<br/>
By just using the function `bool Aircondition_LG::sendCommandAndParameter(char aCommand, int aParameter)` you can control the air conditioner by any other command source.<br/>
The file *acLG.h* contains the command documentation of the LG air conditioner IR protocol. Based on reverse engineering of the LG AKB73315611 remote.
- Do not open an issue without first testing some of the examples!
- If you have a problem, please post the MCVE (Minimal Complete Verifiable Example) showing this problem. My experience is, that most of the times you will find the problem while creating this MCVE :smile:.
- [Use code blocks](https://github.com/adam-p/markdown-here/wiki/Markdown-Cheatsheet#code); **it helps us help you when we can read your code!**
| `RAW_BUFFER_LENGTH` | 100 | Buffer size of raw input buffer. Must be even! 100 is sufficient for *regular* protocols of up to 48 bits, but for most air conditioner protocols a value of up to 750 is required. Use the ReceiveDump example to find smallest value for your requirements. |
| `EXCLUDE_UNIVERSAL_PROTOCOLS` | disabled | Excludes the universal decoder for pulse distance protocols and decodeHash (special decoder for all protocols) from `decode()`. Saves up to 1000 bytes program memory. |
| `DECODE_<Protocol name>` | all | Selection of individual protocol(s) to be decoded. You can specify multiple protocols. See [here](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/master/src/IRremote.hpp#L98-L121) |
| `MARK_EXCESS_MICROS` | 20 | MARK_EXCESS_MICROS is subtracted from all marks and added to all spaces before decoding, to compensate for the signal forming of different IR receiver modules. |
| `RECORD_GAP_MICROS` | 5000 | Minimum gap between IR transmissions, to detect the end of a protocol.<br/>Must be greater than any space of a protocol e.g. the NEC header space of 4500 <20>s.<br/>Must be smaller than any gap between a command and a repeat; e.g. the retransmission gap for Sony is around 24 ms.<br/>Keep in mind, that this is the delay between the end of the received command and the start of decoding. |
| `IR_INPUT_IS_ACTIVE_HIGH` | disabled | Enable it if you use a RF receiver, which has an active HIGH output signal. |
| `IR_SEND_PIN` | disabled | If specified (as constant), reduces program size and improves send timing for AVR. If you want to use a runtime variable send pin e.g. with `setSendPin(uint8_t aSendPinNumber)` , you must disable this macro. |
| `SEND_PWM_BY_TIMER` | disabled | Disables carrier PWM generation in software and use (restricted) hardware PWM. Enabled for ESP32 and RP2040 in all examples. |
| `USE_NO_SEND_PWM` | disabled | Uses no carrier PWM, just simulate an **active low** receiver signal. Overrides `SEND_PWM_BY_TIMER` definition. |
| `USE_OPEN_DRAIN_OUTPUT_FOR_SEND_PIN` | disabled | Uses or simulates open drain output mode at send pin. **Attention, active state of open drain is LOW**, so connect the send LED between positive supply and send pin! |
| `EXCLUDE_EXOTIC_PROTOCOLS` | disabled | Excludes BOSEWAVE, WHYNTER and LEGO_PF from `decode()` and from sending with `IrSender.write()`. Saves up to 650 bytes program memory. |
| `FEEDBACK_LED_IS_ACTIVE_LOW` | disabled | Required on some boards (like my BluePill and my ESP8266 board), where the feedback LED is active low. |
| `NO_LED_FEEDBACK_CODE` | disabled | Disables the LED feedback code for send and receive. Saves around 100 bytes program memory for receiving, around 500 bytes for sending and halving the receiver ISR processing time. |
| `TOLERANCE_FOR_DECODERS_MARK_OR_SPACE_MATCHING` | 25 | Relative tolerance (in percent) for matchTicks(), matchMark() and matchSpace() functions used for protocol decoding. |
### Modifying compile options / macros with PlatformIO
If you are using PlatformIO, you can define the macros in the *[platformio.ini](https://docs.platformio.org/en/latest/projectconf/section_env_build.html)* file with `build_flags = -D MACRO_NAME` or `build_flags = -D MACRO_NAME=macroValue`.
### Modifying compile options / macros with Sloeber IDE
If you are using [Sloeber](https://eclipse.baeyens.it) as your IDE, you can easily define global symbols with *Properties > Arduino > CompileOptions*.<br/>
**Issues and discussions with the content "Is it possible to use this library with the ATTinyXYZ? / board XYZ" without any reasonable explanations will be immediately closed without further notice.**<br/>
ATtiny and Digispark boards are only tested with the recommended [ATTinyCore](https://github.com/SpenceKonde/ATTinyCore) using `New Style` pin mapping for the pro board.
- ESP8266 [This fork](https://github.com/crankyoldgit/IRremoteESP8266) supports an [impressive set of protocols and a lot of air conditioners](https://github.com/crankyoldgit/IRremoteESP8266/blob/master/SupportedProtocols.md)
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.<br/>
If you can provide **examples of using a periodic timer for interrupts** for the new board, and the board name for selection in the Arduino IDE, then you have way better chances to get your board supported by IRremote.
The **receiver sample interval of 50 <20>s is generated by a timer**. On many boards this must be a hardware timer. On some boards where a software timer is available, the software timer is used.<br/>
The code for the timer and the **timer selection** is located in [private/IRTimer.hpp](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/master/src/private/IRTimer.hpp). It can be adjusted here.<br/>
**Be aware that the hardware timer used for receiving should not be used for analogWrite()!**.<br/>
The **send PWM signal** is by default generated by software. **Therefore every pin can be used for sending**.
The PWM pulse length is guaranteed to be constant by using `delayMicroseconds()`.
Take care not to generate interrupts during sending with software generated PWM, otherwise you will get jitter in the generated PWM.
E.g. wait for a former `Serial.print()` statement to be finished by `Serial.flush()`.
Since the Arduino `micros()` function has a resolution of 4 <20>s at 16 MHz, we always see a small jitter in the signal, which seems to be OK for the receivers.
| Software generated PWM showing small jitter because of the limited resolution of 4 <20>s of the Arduino core `micros()` function for an ATmega328 | Detail (ATmega328 generated) showing 30% duty cycle |
If you use a library which requires the same timer as IRremote, you have a problem, since **the timer resource cannot be shared simultaneously** by both libraries.
The best approach is to change the timer used for IRremote, which can be accomplished by modifying the timer selection in [private/IRTimer.hpp](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/master/src/private/IRTimer.hpp).<br/>
The modification must be renewed for each new IRremote library version, or you use an IDE like [Sloeber](https://github.com/Arduino-IRremote/Arduino-IRremote#modifying-compile-options--macros-with-sloeber-ide).<br/>
Another approach can be to share the timer **sequentially** if their functionality is used only for a short period of time like for the **Arduino tone() command**.
An example can be seen [here](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/21b5747a58e9d47c9e3f1beb056d58c875a92b47/examples/ReceiveDemo/ReceiveDemo.ino#L159-L169), where the timer settings for IR receive are restored after the tone has stopped.
Due to automatic gain control and other bias effects, high intensity of the 38 kHz pulse counts more than medium intensity (e.g. 50% duty cycle) at the same total energy.
**The best way to increase the IR power for free** 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.<br/>
To keep the current for 2 diodes with 1.3 volt and 25 mA and a 5 volt supply, you must reduce the resistor by factor: (5V - 1.3V) / (5V - 2.6V) = 1.5 e.g. from 150 ohm to 100 ohm.<br/>
For 3 diodes it requires factor 2.5 e.g. from 150 ohm to 60 ohm.<br/>
Or compute it directly with the **U = R * I formula**. Here U is (5V - <number_of_diodes>* 1.3V) at moderate current, at higher currents you must choose more than 1.3 volt. If you want to be exact, you must check the datasheet of your diode for the appropriate **forward voltage fo a given current**.
The IR signal is sampled at a **50 <20>s interval**. For a constant 525 <20>s pulse or pause we therefore get 10 or 11 samples, each with 50% probability.<br/>
Therefore **we decode by default with a +/- 25% margin** using the formulas [here](https://github.com/Arduino-IRremote/Arduino-IRremote/blob/master/src/IRremoteInt.h#L376-L399).<br/>
E.g. for the NEC protocol with its 560 <20>s unit length, we have TICKS_LOW = 8.358 and TICKS_HIGH = 15.0. This means, we accept any value between 8 ticks / 400 <20>s and 15 ticks / 750 <20>s (inclusive) as a mark or as a zero space. For a one space we have TICKS_LOW = 25.07 and TICKS_HIGH = 45.0.<br/>
And since the receivers generated marks are longer or shorter than the spaces, we have introduced the [`MARK_EXCESS_MICROS` value]/https://github.com/Arduino-IRremote/Arduino-IRremote#protocolunknown)
to compensate for this receiver (and signal strength as well as ambient light dependent :disappointed: ) specific deviation. Welcome to the basics of **real world signal processing**.
[Here](https://github.com/crankyoldgit/IRremoteESP8266) you find an **ESP8266/ESP32** version of IRremote with an **[impressive list of supported protocols](https://github.com/crankyoldgit/IRremoteESP8266/blob/master/SupportedProtocols.md)**.
I created this comparison matrix for [myself](https://github.com/ArminJo) in order to choose a small IR lib for my project and to have a quick overview, when to choose which library.<br/>
| FLASH usage (simple NEC example with 5 prints) | 1820<br/>(4300 for 15 main / 8000 for all 40 protocols)<br/>(+200 for callback)<br/>(+80 for interrupt at pin 2+3)| 1270<br/>(1400 for pin 2+3) | 4830 | 1770 | **900** | ?1100? |
| Remarks | Decodes 40 protocols concurrently.<br/>39 Protocols to send.<br/>Work in progress. | Only one protocol at a time. | Consists of 5 libraries. **Project containing bugs - 45 issues, no reaction for at least one year.** | Decoding and sending are easy to extend.<br/>Supports **Pronto** codes. | Requires no timer. | Requires no timer. |
\* The Hash protocol gives you a hash as code, which may be sufficient to distinguish your keys on the remote, but may not work with some protocols like Mitsubishi
- [IRMP list of IR protocols](https://www.mikrocontroller.net/articles/IRMP_-_english#IR_Protocols]
- [IR Remote Control Theory and some protocols (upper right hamburger icon)](https://www.sbprojects.net/knowledge/ir/)
- [Interpreting Decoded IR Signals (v2.45)](http://www.hifi-remote.com/johnsfine/DecodeIR.html)
- ["Recording long Infrared Remote control signals with Arduino"](https://www.analysir.com/blog/2014/03/19/air-conditioners-problems-recording-long-infrared-remote-control-signals-arduino)
- The original blog post of Ken Shirriff [A Multi-Protocol Infrared Remote Library for the Arduino](http://www.arcfn.com/2009/08/multi-protocol-infrared-remote-library.html)
