i2c

Native bindings for i2c-dev. Plays well with Raspberry Pi and BeagleBone.

Install

npm install i2c

Requires Node.js >= 18 and a Linux system with I2C support. The native addon uses Node-API for ABI stability across Node.js versions — no recompilation needed when upgrading Node.js.

Usage

const I2C = require('i2c');
const address = 0x18;
const wire = new I2C(address, { device: '/dev/i2c-1' });

wire.on('open', () => {
  // device is ready

  wire.scan((err, data) => {
    // data contains an array of detected device addresses
  });

  wire.writeByte(byte, (err) => {});

  wire.writeBytes(command, [byte0, byte1], (err) => {});

  wire.readByte((err, res) => {
    // res is a single byte
  });

  wire.readBytes(command, length, (err, res) => {
    // res contains a buffer of bytes
  });

  // plain read/write
  wire.write([byte0, byte1], (err) => {});

  wire.read(length, (err, res) => {
    // res contains a buffer of bytes
  });

  // continuous streaming
  wire.on('data', (data) => {
    // data contains: { address, data, cmd, length, timestamp }
  });

  wire.stream(command, length, delay); // delay in ms (default: 100)
  wire.stopStream(); // stop streaming
});

Raspberry Pi Setup

Enable I2C on Raspberry Pi OS:

sudo raspi-config

Navigate to Interface Options > I2C and select Yes to enable.

Alternatively, enable manually:

sudo dtparam i2c_arm=on
sudo modprobe i2c-dev

To load i2c-dev automatically on boot, add it to /etc/modules-load.d/:

echo "i2c-dev" | sudo tee /etc/modules-load.d/i2c.conf

Verify the I2C bus is available:

ls /dev/i2c-*

Install I2C tools for debugging:

sudo apt install i2c-tools
i2cdetect -y 1

By default, the I2C device requires root access. To allow non-root users, add your user to the i2c group:

sudo usermod -aG i2c $USER

Log out and back in for the group change to take effect.

Device path

The default device path is /dev/i2c-1, which is correct for most Raspberry Pi models (2 and later). For the original Raspberry Pi (rev 1), use /dev/i2c-0:

new I2C(address, { device: '/dev/i2c-0' }); // RPi rev 1
new I2C(address, { device: '/dev/i2c-1' }); // RPi 2+ (default)

BeagleBone Setup

I2C is enabled by default on BeagleBone. Install Node.js and the package:

npm install i2c

The I2C buses are available at /dev/i2c-0, /dev/i2c-1, and /dev/i2c-2 depending on your BeagleBone variant. Use i2cdetect to verify:

i2cdetect -l

Projects using i2c

• bonescript — Physical computing library for BeagleBone (GitHub)
• mpu6050 — MPU-6050 accelerometer/gyroscope (GitHub)
• adxl345 — ADXL345 accelerometer (GitHub)
• mcp3424 — MCP3424 ADC (GitHub)
• blinkm — BlinkM LED controller (GitHub)

Contributors

Thanks to @alphacharlie, @J-Cat, and all contributors.

Questions?

http://www.twitter.com/korevec