Promised Bus and Device factories for i2c-bus.
This package replaces i2c-bus-promised
Choose your flavour, yarn:
yarn add async-i2c-bus
or npm:
npm i -P async-i2c-bus
And you're ready to go.
The package requires node v8.10.x
or higher.
If you need a compatibility with lower versions of node, you can build it. To do so clone the repo in your workspace, and modify the target
options in the tsconfig.json
, e.g:
{
"compilerOptions": {
"target": "es5", // <-- Line changed
"outDir": "dist/main",
"rootDir": "src",
// ..
}
}
And build the module with yarn build
or npm run build
.
The package exports the Bus
factory to create a BusInterface
. The BusInterface
is an object with the same methods available in the original i2c-bus
but promised. The signature of the factory is the following:
const Bus = ({ busNumber = 1, openBus = openI2cBus } = {}): BusInterface
busNumber
is the i2c bus number, and defaults to 1. Unless your devices has more than one bus, it will suit you.openBus
is the function to open the bus. It defaults toi2c.openBus
, but it would accept any function with the same signature. You shouldn't pass this value, except if you're in a testing environment.
The package also exports the Device
factory to create a DeviceInterface
. This is a helper method to call the i2cBus
methods with the address of your device. It has the following signature:
const Device = ({ address, bus }: { address: number; bus: BusInterface }): DeviceInterface
You don't need to use a DeviceInterface
in order to work with this library, but it helps.
For more details, check the full auto-generated documentation.
const WEATHER_SENSOR_ADDRESS = 0x77;
const main = async () => {
const bus = Bus();
await bus.open();
const devices = await bus.scan();
console.log(`Connected devices ${devices}`);
const weatherSensor = Device({ 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}`);
};
Also you can extend your device to implement specific methods. Take the previous case:
const WeatherSensor = ({ bus }) => ({
...Device({ address: 0x77, bus }),
async init() {
await this.writeByte(0xf4, 0b00100101);
await this.writeByte(0xf5, 0b00100100);
return this;
},
async readTemperature() {
const buffer = Buffer.alloc(3);
await this.readI2cBlock(0xfa, 3, buffer);
return buffer.readUIntBE(0, 3) >>> 4;
},
});
const main = async () => {
const bus = Bus();
await bus.open();
const weatherSensor = await WeatherSensor({ bus }).init();
const temperature = await weatherSensor.readTemperature();
console.log(`Temperature: ${temperature}`);
};
Testing i2c code can be expensive and slow. It may take some time to deploy and run your e2e tests/code in a low powered device. For that, you can use the createI2cBusMock
function and write some unit tests. Although you shouldn't relay too much on the values read and written (it works as if the i2c bus is just a memory), it can help you to test that the right functions are being invoked.
import { Bus, Device } from '../dist/main';
jest.mock('i2c-bus', () => {
const createI2cBusMock = require('../dist/main/lib/createI2cBusMock').default; // eslint-disable-line global-require
return {
open: createI2cBusMock({
devices: {
0xab: Buffer.allocUnsafe(0xff),
},
}),
};
});
describe('Device', () => {
it('should write the right command', async () => {
const busNumber = 1;
const bus = Bus({ busNumber });
const address = 0xab;
const device = Device({ address, bus });
await bus.open();
const spyOnWriteByte = jest.spyOn(bus, 'writeByte');
await device.writeByte(0x0f, 0xff);
expect(spyOnWriteByte).toHaveBeenCalledWith(address, 0x0f, 0xff);
});
});