Pi-IO

A proof of concept to demonstrate that it's feasible to implement a Raspberry Pi IO Plugin for Johnny-Five using Linux-IO.

Tested on a Raspberry Pi 4 Model B with Node.js v16.0.0. Should function with Node.js v10 or higher.

Installation

Step 1 - Install the pigpio C library

The pigpio C library is a prerequisite for pi-io.

Run the following command to determine which version of the pigpio C library is installed:

pigpiod -v

For the Raspberry Pi Zero, 1, 2 and 3 V41 or higher of the pigpio C library is required. For the Raspberry Pi 4 V69 or higher is required.

If the pigpio C library is not installed or if the installed version is too old, the latest version can be installed with the following commands:

sudo apt-get update
sudo apt-get install pigpio

Alternative installation instructions for the pigpio C library can be found here.

Warning: The pigpio C library contains a number of utilities. One of these utilities is pigpiod which launches the pigpio C library as a daemon. This utility should not be used as the pi-io uses the pigpio C library directly.

Step 2 - Install the pi-io Node.js package

npm install pi-io

Johnny-Five Features Supported

Feature	Support
Analog Read	no
Digital Read	yes
Digital Write	yes
PWM	yes
Servo	yes
I2C	yes
One Wire	no
Stepper	no
Serial/UART	no
DAC	no
Ping	yes *)

*) Ping was tested with three HC-SR04 proximity sensors with varying degrees of success. One sensor functioned as expected. The second didn't timeout as it should but it's was possible to workaround the issue with software. The third sensor didn't function. The issues may be related to the fact that a single pin is used for both trigger and echo.

To workaround these issues a controller was implemented that allows separate pins to be used for trigger and echo. The same three HC-SR04 proximity sensors functioned well with this controller.

Supported Pins

Pin ID	Supported Modes	Comments
P1-3 or GPIO2	INPUT, OUTPUT, PWM, SERVO	Alternatively I2C SDA1
P1-5 or GPIO3	INPUT, OUTPUT, PWM, SERVO	Alternatively I2C SCL1
P1-7 or GPIO4	INPUT, OUTPUT, PWM, SERVO
P1-8 or GPIO14	INPUT, OUTPUT, PWM, SERVO
P1-10 or GPIO15	INPUT, OUTPUT, PWM, SERVO
P1-11 or GPIO17	INPUT, OUTPUT, PWM, SERVO
P1-12 or GPIO18	INPUT, OUTPUT, PWM, SERVO
P1-13 or GPIO27	INPUT, OUTPUT, PWM, SERVO
P1-15 or GPIO22	INPUT, OUTPUT, PWM, SERVO
P1-16 or GPIO23	INPUT, OUTPUT, PWM, SERVO
P1-18 or GPIO24	INPUT, OUTPUT, PWM, SERVO
P1-19 or GPIO10	INPUT, OUTPUT, PWM, SERVO
P1-21 or GPIO9	INPUT, OUTPUT, PWM, SERVO
P1-22 or GPIO25	INPUT, OUTPUT, PWM, SERVO
P1-23 or GPIO11	INPUT, OUTPUT, PWM, SERVO
P1-24 or GPIO8	INPUT, OUTPUT, PWM, SERVO
P1-26 or GPIO7	INPUT, OUTPUT, PWM, SERVO
P1-29 or GPIO5	INPUT, OUTPUT, PWM, SERVO
P1-31 or GPIO6	INPUT, OUTPUT, PWM, SERVO
P1-32 or GPIO12	INPUT, OUTPUT, PWM, SERVO
P1-33 or GPIO13	INPUT, OUTPUT, PWM, SERVO
P1-35 or GPIO19	INPUT, OUTPUT, PWM, SERVO
P1-36 or GPIO16	INPUT, OUTPUT, PWM, SERVO
P1-37 or GPIO26	INPUT, OUTPUT, PWM, SERVO
P1-38 or GPIO20	INPUT, OUTPUT, PWM, SERVO
P1-40 or GPIO21	INPUT, OUTPUT, PWM, SERVO
LED0	OUTPUT	Built-in LED

Usage

Pluse an LED connected to GPIO17

var five = require('johnny-five');
var PiIO = require('pi-io');

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

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

  led.pulse(1000);
});

Rotate a continuous servo connected to GPIO27 clockwise

var five = require('johnny-five');
var PiIO = require('pi-io');

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

board.on('ready', function() {
  var servo = new five.Servo({
    pin: 'GPIO27',
    type: "continuous"
  });

  servo.cw(0.8);
});

Measure proximity with a HC-SR04 using separate pins for trigger and echo

var five = require('johnny-five');
var PiIO = require('pi-io');

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

board.on('ready', function() {
  var proximity = new five.Proximity({
    controller: PiIO.HCSR04, // Custom controller
    triggerPin: 'GPIO23',
    echoPin: 'GPIO24'
  });

  proximity.on("change", function() {
    console.log("cm: ", this.cm);
  });
});

Measure proximity with a HC-SR04 connected to GPIO25

Note that this circuit uses a single pin for trigger and echo. Whether or not this functions correctly appears to be highly dependent on the particular HC-SR04 sensor being used. The circuit shown above that uses separate pins for trigger and echo is far more reliable.

var five = require('johnny-five');
var PiIO = require('pi-io');

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

board.on('ready', function() {
  var proximity = new five.Proximity({
    controller: 'HCSR04',
    pin: 'GPIO25'
  });

  proximity.on("data", function() {
    console.log("cm: ", this.cm);
  });
});

Examples

Additional examples can be found in the example directory.