Linux-IO

Linux-IO is an extensible Linux IO Plugin for Johnny-Five. It extends board-io to provide Linux implementations for the following features that IO Plugins can support:

• Digital IO
  • Implementation based on the GPIO sysfs interface using onoff
• I2C
  • Implementation based on the /dev interface using i2c-bus
• Built-in LEDs
  • Implementation based on the LED sysfs interface using led.js

The initial motivation for implementing Linux-IO was to provide Linux implementations of the I2C methods that Johnny-Five IO Plugins are required to implement. Over the course of the last two years I was involved in adding I2C functionality to a number of IO Plugins. In reality, more or less the same code was added to each IO Plugin. The goal of Linux-IO is to make such code reusable across Linux IO Plugins.

Linux-IO supports Node.js versions 10, 12, 14, 15 and 18.

Installation

npm install linux-io

Johnny-Five Features Supported

The Johnny-Five features supported by a platform are summarized in tables on the Platform Support page. The features supported by Linux-IO shown in the following table:

Feature | Support :--- | :--- Analog Read | no Digital Read | yes Digital Write | yes PWM | no Servo | no I2C | yes One Wire | no Stepper | no Serial/UART | no DAC | no Ping | no

Usage

Here's a minimalistic IO Plugin for the Raspberry Pi called TinyRaspberryPiIO that allows digital IO on GPIO4 and GPIO17 and I2C serial bus access on I2C bus 1. The built-in LED can also be used.

var LinuxIO = require('linux-io'),
  util = require('util');

function TinyRaspberryPiIO() {
  if (!(this instanceof TinyRaspberryPiIO)) {
    return new TinyRaspberryPiIO();
  }

  LinuxIO.call(this, {
    pins: [{
      ids: ['P1-7', 'GPIO4'],
      gpioNo: 4,
      modes: [0, 1]
    }, {
      ids: ['P1-11', 'GPIO17'],
      gpioNo: 17,
      modes: [0, 1]
    }, {
      ids: ['LED0'],
      ledPath: '/sys/class/leds/led0',
      modes: [1]
    }],
    defaultI2cBus: 1,
    defaultLed: 'LED0'
  });

  setImmediate(function () {
    this.emit('connect');
    this.emit('ready');
  }.bind(this));
}
util.inherits(TinyRaspberryPiIO, LinuxIO);

module.exports = TinyRaspberryPiIO;

If a button is connected to GPIO4 and an LED is connected to GPIO17, the following program will turn the LED on when the button is pressed and turn the LED off when the button is released.

var five = require('johnny-five');
var TinyRaspberryPiIO = require('./tiny-raspberry-pi-io');

var board = new five.Board({
  io: new TinyRaspberryPiIO()
});

board.on('ready', function() {
  var led = new five.Led('GPIO17');
  var button = new five.Button('GPIO4');

  button.on('down', function() {
    led.on();
  });

  button.on('up', function() {
    led.off();
  });
});

If an ADXL345 accelerometer is connected to I2C bus 1, the following program will print information provided by accelerometer.

var five = require('johnny-five');
var TinyRaspberryPiIO = require('./tiny-raspberry-pi-io');

var board = new five.Board({
  io: new TinyRaspberryPiIO()
});

board.on('ready', function() {
  var accelerometer = new five.Accelerometer({
    controller: "ADXL345"
  });

  accelerometer.on("change", function() {
    console.log("accelerometer");
    console.log("  x            : ", this.x);
    console.log("  y            : ", this.y);
    console.log("  z            : ", this.z);
    console.log("  pitch        : ", this.pitch);
    console.log("  roll         : ", this.roll);
    console.log("  acceleration : ", this.acceleration);
    console.log("  inclination  : ", this.inclination);
    console.log("  orientation  : ", this.orientation);
    console.log("--------------------------------------");
  });
});

Examples

Additional examples for the Raspberry Pi, BeagleBone Black and C.H.I.P can be found in the example directory.

IO Plugins Based On Linux-IO

• BeagleBone Black
  • BeagleBone-IO
• Raspberry Pi
  • Pi-IO