usage.md

Usage

The package exports the Bus, Device and BusError classes.

You can check the full documentation

Bus

The Bus wraps the original implementation with a typescript class.

To create a Bus use the static method create or createAndOpen (also opens the bus) with the following signatures:

Bus.create({ busNumber }): Bus

Name	Type
busNumber	number

Returns: Bus

Bus.createAndOpen({ busNumber }): Promise<Bus>

Name	Type
busNumber	number

Returns: Promise‹Bus›

Device

Device inherits all the device-oriented methods from Bus and calls them with the device's address.

Also you can extends / compose it to create your specific device class. Read further for an example of it.

To create a Device use the static method create with the following signature:

Device.create({ busNumber }): Device

Name	Type
bus	bus
address	number

Returns: Device

BusError

All the errors thrown by the bus are wrapped into BusError, which keeps the message and stack of the original error, but makes it easier to catch bus-specific errors.

Example

import { Bus, Device } from 'async-i2c-bus';

const WEATHER_SENSOR_ADDRESS = 0x77;

const main = async () => {
  const bus = Bus.create();

  await bus.open();

  const devices = await bus.scan();

  console.log(`Connected devices ${devices}`);

  const weatherSensor = Device.create({ address: WEATHER_SENSOR_ADDRESS, bus });

  // Configure Weather Sensor (BMP280)
  await weatherSensor.writeByte(0xf4, 0b00100101);
  await weatherSensor.writeByte(0xf5, 0b00100100);

  // Read temperature
  const temperatureBuffer = Buffer.alloc(3);
  await weatherSensor.readI2cBlock(0xfa, 3, temperatureBuffer);
  const temperature = temperatureBuffer.readUIntBE(0, 3) >>> 4;

  console.log(`Temperature: ${temperature}`);
};

Example using custom device

import { Device } from 'async-i2c-bus';

const WEATHER_SENSOR_ADDRESS = 0x77;

class WeatherSensor {
  constructor({ bus }) {
    this.device = Device.create({ bus, address: WEATHER_SENSOR_ADDRESS });
  }

  async readTemperature() {
    const buffer = Buffer.alloc(3);

    await this.bus.readI2cBlock(0xfa, 3, buffer);

    return buffer.readUIntBE(0, 3) >>> 4;
  }
}