rpio2

Control Raspberry Pi GPIO pins with node.js. Fast and easy to use.

Usage no npm install needed!

<script type="module">
  import rpio2 from 'https://cdn.skypack.dev/rpio2';
</script>

README

rpio2

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Export elegant OOP APIs to control Raspberry Pi GPIO pins with Node.js. Based on node-rpio which is a high performace library.

Installation

npm install rpio2 --production

By default the module will use /dev/gpiomem when using simple GPIO access. To access this device, your user will need to be a member of the gpio group, and you may need to configure udev with the following rule (as root):

$ cat >/etc/udev/rules.d/20-gpiomem.rules <<EOF
SUBSYSTEM=="bcm2835-gpiomem", KERNEL=="gpiomem", GROUP="gpio", MODE="0660"
EOF

For access to i²c, PWM, and SPI, or if you are running an older kernel which does not have the bcm2835-gpiomem module, you will need to run your programs as root for access to /dev/mem.

Usage

Synchronously

const Gpio = require('./lib/index.js').Gpio;
const gpio = new Gpio(40);

gpio.open(Gpio.OUTPUT);

for(var i = 0; i < 10; i++){
    gpio.toggle();
    gpio.sleep(500);
}

gpio.close();

Asynchronously

const Gpio = require('../lib/index.js').Gpio;
const gpio = new Gpio(40);

gpio.open(Gpio.OUTPUT);

void function loop(){
  Promise.resolve(gpio.toggle())
  .then(gpio.sleep.bind(null, 500, true))
  .then(loop)
}();

process.on("SIGINT", function(){
  gpio.close();

  console.log('shutdown!');
  process.exit(0);
});

Toggle with button

const Gpio = require('../lib/index.js').Gpio;
const button = new Gpio(32);
const output = new Gpio(40);

button.open(Gpio.INPUT);
output.open(Gpio.OUTPUT, Gpio.LOW);

//button down
button.on('rising', function(){
  output.toggle();
});

process.on("SIGINT", function(){
  button.close();
  output.close();

  console.log('shutdown!');
  process.exit(0);
});

API

Class Gpio extends events.EventEmitter

Methods

Statics

Properties

Events

Constants

  • Gpio.UNKNOWN = -1;
  • Gpio.HIGH = 1;
  • Gpio.LOW = 0;
  • Gpio.INPUT = 0;
  • Gpio.OUTPUT = 1;
  • Gpio.PULL_OFF = 0;
  • Gpio.PULL_DOWN = 1;
  • Gpio.PULL_UP = 2;
  • Gpio.PULL_DEFAULT = -1;
  • Gpio.POLL_NONE = 0;
  • Gpio.POLL_LOW = 1;
  • Gpio.POLL_HIGH = 2;
  • Gpio.POLL_BOTH = 3;

Class GpioGroup

Gpio(pin[,activeLow])

new Gpio(pin[,activeLow]) creates a GPIO pin instance. The arguments pin use the physical numbering (P01-P40) by default:

let pin1 = new Gpio(40); //create P40 (gpio21)

The option parameter activeLow specifies whether the values read from or written to the GPIO should be inverted. The interrupt generating edge for the GPIO also follow this setting. The valid values for activeLow are true and false. Setting activeLow to true inverts. The default value is false.

The pin number mapping to GPIO number as below (Pi2 B+):

+ 3.3v12+ 5v
I2C SDA / GPIO 23 4+ 5v
I2C SCL / GPIO 356Ground
Clock / GPIO 478TX / GPIO 14
--910RX / GPIO 15
GPIO 171112GPIO 18
GPIO 271314--
GPIO 221516GPIO 23
+ 3.3V1718GPIO 24
SPI MOSI / GPIO 101920--
SPI MISO / GPIO 92122GPIO 25
SPI SCLK / GPIO 112324SPI CE0 / GPIO 8
--2526SPI CE1 / GPIO 7
Model A+ and Model B+ additional pins
ID_SD2728ID_SC
GPIO 52930--
GPIO 63132GPIO 12
GPIO 133334--
GPIO 193536GPIO 16
GPIO 263738GPIO 20
--3940GPIO 21

If you want to map to gpio number directly, see Gpio.init(options)

Methods

open(mode[, state])

Open a pin for input or output. Valid modes are:

  • Gpio.INPUT: pin is input (read-only).
  • Gpio.OUTPUT: pin is output (read-write).

For output pins, the second parameter defines the initial value of the pin, rather than having to issue a separate .write() call. This can be critical for devices which must have a stable value, rather than relying on the initial floating value when a pin is enabled for output but hasn't yet been configured with a value.

For input pins, the second parameter can be used to configure the internal pullup or pulldown resistors state, see mode:0|1 state:0|1 for more details.

close()

Unexports a GPIO from userspace and release all resources.

read()

Set a velue to a GPIO.

write(value)

Set a velue to a GPIO.

toggle()

Change GPIO value.

sleep(ms[,async])

Sleep for a few milliseconds. If async is true, it will return a promise.

createReadStream(pin[, options])

Experimental. See the following example:

log input value to stdout

const Gpio = require('../lib/index.js').Gpio;

var gs = Gpio.createReadStream(32, {throttle: 100});

gs.pipe(process.stdout);

process.on("SIGINT", function(){
  gs.end();
  process.exit(0);
});
createWriteStream(pin[, options])

Experimental. See the following example:

read from stdin and set value

const Gpio = require('../lib/index.js').Gpio;

var gs = Gpio.createWriteStream(40, {
  mode: Gpio.OUTPUT,
  state: Gpio.HIGH
});

console.log('Please input value of P40.');

process.stdin.pipe(gs);

process.on("SIGINT", function(){
  gs.end();
  process.exit(0);
});

trace input/output pins

const Gpio = require('../lib/index.js').Gpio;

var input = Gpio.createReadStream(32, {throttle: 100});

var output = Gpio.createWriteStream(40);

input.pipe(output);

process.on("SIGINT", function(){
  input.end();
  output.end();
  process.exit(0);
});
group(pins[, activeLow])

Create GpioGroup instance. See GpioGroup(pins[, activeLow]) - Constructor.

Properties

value:0|1

Get or set a velue to a GPIO synchronously.

mode:0|1

The pin direction, pass either Gpio.INPUT for read mode or Gpio.OUTPUT for write mode.

state:0|1

The pin state. For input pins, state can be either Gpio.POLL_HIGHT or Gpio.POLL_LOW. For output pins, it is equivalent to value that state can be either Gpio.HIGH or Gpio.LOW.

activeLow: boolean

Specifies whether the values read from or written to the GPIO should be inverted. The interrupt generating edge for the GPIO also follow this this setting. The valid values for activeLow are true and false. Setting activeLow to true inverts. The default value is false.

Statics

Gpio.init([options])

Initialise the bcm2835 library. This will be called automatically by .open() using the default option values if not called explicitly. The default values are:

var options = {
        gpiomem: true,          /* Use /dev/gpiomem */
        mapping: 'physical',    /* Use the P1-P40 numbering scheme */
}
gpiomem

There are two device nodes for GPIO access. The default is /dev/gpiomem which, when configured with gpio group access, allows users in that group to read/write directly to that device. This removes the need to run as root, but is limited to GPIO functions.

For non-GPIO functions (i²c, PWM, SPI) the /dev/mem device is required for full access to the Broadcom peripheral address range and the program needs to be executed as the root user (e.g. via sudo). If you do not explicitly call .init() when using those functions, the library will do it for you with gpiomem: false.

You may also need to use gpiomem: false if you are running on an older Linux kernel which does not support the gpiomem module.

rpio will throw an exception if you try to use one of the non-GPIO functions after already opening with /dev/gpiomem, as well as checking to see if you have the necessary permissions.

Valid options:

  • true: use /dev/gpiomem for non-root but GPIO-only access
  • false: use /dev/mem for full access but requires root
mapping

There are two naming schemes when referring to GPIO pins:

  • By their physical header location: Pins 1 to 26 (A/B) or Pins 1 to 40 (A+/B+)
  • Using the Broadcom hardware map: GPIO 0-25 (B rev1), GPIO 2-27 (A/B rev2, A+/B+)

Confusingly however, the Broadcom GPIO map changes between revisions, so for example P3 maps to GPIO0 on Model B Revision 1 models, but maps to GPIO2 on all later models.

This means the only sane default mapping is the physical layout, so that the same code will work on all models regardless of the underlying GPIO mapping.

If you prefer to use the Broadcom GPIO scheme for whatever reason (e.g. to use the P5 header pins on the Raspberry Pi 1 revision 2.0 model which aren't currently mapped to the physical layout), you can set mapping to gpio to switch to the GPIOxx naming.

Valid options:

  • gpio: use the Broadcom GPIOxx naming
  • physical: use the physical P01-P40 header layout
Gpio.sleep(ms[,async])

Sleep for a few milliseconds. If async is true, it will return a promise.

Events

If a pin is in direction of Gpio.DIR_IN. Three type of events can be fired when needed.

event:rising

When register listener to rising event the rising interrupt edges should be configured implictly and the GPIO will trigger the rising event.

gpio.on('rising', function(){
  console.log('A rising signal detected!');
});
event:falling

When register listener to falling event the falling interrupt edges should be configured implictly and the GPIO will trigger the falling event.

event:change

When register listener to change event the both(rising and falling) interrupt edges should be configured implictly and the GPIO will trigger the change event(on both rising and falling edges).

Note:

Registering events to rising and falling will implictly change the interrupt edges as well as unregistering events:

let gpio = new Gpio(40);
gpio.open(Gpio.INPUT);
assertEqual(gpio.edge, Gpio.POLL_NONE); 
gpio.on('rising', function(){...});
assertEqual(gpio.edge, Gpio.POLL_HIGH); 
gpio.on('falling', function(){...});
assertEqual(gpio.edge, Gpio.POLL_BOTH);
gpio.removeListener('rising');
assertEqual(gpio.edge, Gpio.POLL_LOW);
gpio.removeListener('falling'); 
assertEqual(gpio.edge, Gpio.POLL_NONE);
GpioGroup(pins, activeLow)

Experimental. See the following example:

var GpioGroup = require('./lib/index.js').GpioGroup;
var pins = [32, 40, 33]; //RGB
var group = new GpioGroup(pins, true);
group.open(GpioGroup.OUTPUT);

var color = {
  yellow: 0b110,
  red: 0b100,
  green: 0b010
};

function turn(color){
  return new Promise(function(resolve, reject) {
   group.value = color;
    resolve();
  })
}
function wait(time){
  return new Promise(function(resolve, reject) {
    setTimeout(resolve,time);
  })
}

void function (){
    turn(color.green)
    .then(wait.bind(null, 5000))
    .then(turn.bind(null, color.yellow))
    .then(wait.bind(null, 2000))
    .then(turn.bind(null, color.red))
    .then(wait.bind(null, 5000))
    .then(arguments.callee)
}();

process.on("SIGINT", function(){
  group.close();

  console.log('shutdown!');
  process.exit(0);
});

LICENSE

GPL