Table of Contents

M5Stack ATOM QR Code reader

This is a library to interact with the ATOM QR Code reader from M5Stack.



  • The module documentation can be found here


Important: make sure you properly setup the UART pins for ESP32 before creating the QrCodeReader. For this, make sure you install the nanoFramework.Hardware.ESP32 NuGet:

// when connecting to an ESP32 device, need to configure the UART GPIOs
// the GPIOs below are the ones from the ATOM device that's part of the
// ATOM QR Code reader kit from M5Stack.
Configuration.SetPinFunction(22, DeviceFunction.COM2_RX);
Configuration.SetPinFunction(19, DeviceFunction.COM2_TX);

For other devices, like STM32, please make sure you're using the pins for the UART you want to use.

using Iot.Device.AtomQrCode;
using nanoFramework.Hardware.Esp32;

// reader is connected to COM2
QrCodeReader reader = new QrCodeReader("COM2");

The reader offers various options to work with. Let's explore the most common usage scenarios.

Reading a barcode

To perform readings "on-demand" the trigger mode has to be set to Host and then calling TryReadBarcode().

// set scan mode to HOST so it reads on request
reader.TriggerMode = TriggerMode.Host;

// try reading barcode
string code;

if (reader.TryReadBarcode(out code))
    Debug.WriteLine("*** failed to read barcode ***");

Upon successful decoding a barcode, it will return the barcode data. On failure an empty string is returned.

Continuous scanning

For random readings when there is no previous knowledge when there is barcode present (for example on a kiosk) one has to set the trigger mode to Automatic, setup an event handler and then call StartScanning().

// set scan mode to AUTOSENSING 
reader.TriggerMode = TriggerMode.Autosensing;

// setup handler
reader.BarcodeDataAvailable += Reader_BarcodeDataAvailable;

// start scanning

The scanner will detect changes in the brightness of the surroundings and will trigger a reading when the brightness changes. Upon successful decoding a barcode, an event is triggered with the barcode data on the respective argument.

void Reader_BarcodeDataAvailable(object sender, BarcodeDataAvailableEventArgs e)
    Debug.WriteLine("*** barcode data received ***");

Settings and configurations

The library exposes several configurations and working options for the reader through properties and commands. Please explore the documentation here.


The development of this library was kindly sponsored by greenYng!