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Arduino Uno R4 · IR Receiver

Arduino Uno R4 IR Receiver Simulator: Wiring, Code and a Live Circuit

This is a 38 kHz IR receiver wired to an Arduino Uno R4 Minima with a remote control beside it, decoded live with the IRremote library: open it in the editor, press a button on the remote, and the serial monitor prints its command code.

Three wires to the receiver: power, GND, and OUT to pin 2. The remote speaks NEC, the protocol of most cheap kit remotes.

Run it in the editorRead the code
  • 5 V logic
  • Library: IRremote.hpp
  • OUT on pin 2
  • NEC protocol, 38 kHz
Arduino Uno R4 · IR Receiverlive0.000 s 0.00x
Click to open it in the editor
The circuit itself, running on the simulator with the sketch below. Press what can be pressed; click anything else to open it in the editor.

Wiring the IR Receiver to the Arduino Uno R4

Every connection in the circuit above, with the board’s own pin names.

IR Receiver pinArduino Uno R4 pinWhy
VCC5VThe VS1838B-style receiver runs from 2.7 to 5.5 V.
GNDGNDGround.
OUTpin 2Low while a 38 kHz burst arrives, high otherwise: the demodulated code.
IR (light)The remoteIn the editor the infrared light path is drawn as a gray wire from the remote.

The receiver runs from the Arduino Uno R4’s 5V pin and its output idles at 5 V, which the board reads directly.

Pins to leave alone on the Arduino Uno R4

An Uno sketch’s source builds for the R4, but a compiled Uno program will not run on it: different chip. The R4’s pins source less current than an Uno’s, about 8 mA each, so do not drive a relay coil or a motor straight from one.

On a real bench

The Uno R4 Minima fits every Uno shield and every Uno breadboard layout, so wire the IR Receiver exactly as you would on an Uno R3. It has a USB-C socket, and its VIN accepts up to 24 V where an Uno R3 stops at 12.

The code

The sketch the circuit above runs. Open it in the editor, change a line and press Run: it compiles in your browser.

IR receiver on Arduino Uno R4 pin 2
#include <IRremote.hpp>

const int IR_PIN = 2;   // OUT, pin 2

void setup() {
  Serial.begin(9600);
  IrReceiver.begin(IR_PIN);
  Serial.println("Point the remote and press a button");
}

void loop() {
  if (IrReceiver.decode()) {
    if (!(IrReceiver.decodedIRData.flags & IRDATA_FLAGS_IS_REPEAT)) {
      Serial.print("Command: 0x");
      Serial.println(IrReceiver.decodedIRData.command, HEX);
    }
    IrReceiver.resume();   // ready for the next one
  }
}

IrReceiver.begin(IR_PIN) starts the IRremote library listening on the pin. decode() returns true once a whole code has arrived, and decodedIRData.command holds the button’s command byte, 0x47 for the button pressed in this demo.

Holding a button makes an NEC remote send short repeat frames, which the library flags with IRDATA_FLAGS_IS_REPEAT. The sketch prints only the first frame of each press. resume() must be called after each code or nothing more is decoded.

Serial.begin(9600) opens the serial monitor. Serial is the USB port; Serial1 is on pins 0 and 1, which on the R4 are free for other serial devices.

Common mistakes with the IR Receiver on the Arduino Uno R4

Old IRremote code

Sketches written for IRremote 2.x use IRrecv irrecv(pin), irrecv.enableIRIn() and results.value. Version 3 and later use IrReceiver and decodedIRData, as here. Mixing the two is the most common reason an IR sketch will not compile.

Forgetting resume()

After decode() returns true, the library holds the code until resume() is called. Leave it out and the first button press is the only one you ever see.

Expecting an Uno’s pin current

The R4’s pins are 5 V like an Uno’s, but each one sources only about 8 mA where an Uno’s gives 20. A signal line to the receiver output is fine; an LED or a coil hung straight off the pin is not.

Questions and answers

Can I simulate an IR remote with an Arduino Uno R4 Minima?

Yes. The circuit at the top of this page is an Arduino Uno R4 Minima with a IR receiver and remote, running in your browser on a simulated Renesas RA4M1 (Cortex-M4). Click a button on the simulated remote: it sends a real NEC frame, which the receiver demodulates onto the pin. Press Run it in the editor to change the wiring or the code; it is free and needs no account.

How do I find my remote’s codes?

Run this sketch and press each button: the command printed is the code to compare against. Address and command are both in decodedIRData if you need to tell two remotes apart.

Why does every press print FFFFFFFF?

That is the repeat code of an NEC remote as old versions of the library reported it. The current library flags repeats instead, which the sketch checks.

Which receiver is this?

A three-pin 38 kHz demodulating receiver like the VS1838B or TSOP38238. Check the pin order on yours: it differs between makers.

Build your own IR Receiver project

Open this circuit in the editor, change the wiring or the code, and keep your version in a free account.

Start building freeOpen the editor