JavaScript Robotics: Pin API (Johnny-Five)

Parameters
Shape
Component Initialization
Usage
API
Events

The Pin class constructs objects that represent any one pin on the physical board.

For most cases, a proper Component class should be used instead of Pin.

Parameters

pin A Number or String address for the pin. If digital, use the number, if analog use the "A" prefixed string.

options An object of property parameters.

Property	Type	Value/Description	Default	Required
id	Number, String	Non-specific. Any string or number value. Defaults to `null`		no
pin	Number, String	Any Pin. The Number or String address of the pin, defaults to 0, or addr when that is supplied	no
board	Object Instance	The board instance your Pin is connected to. Only required when multiple boards are mounted in your project.	First board mounted	no
type	String	"digital", "analog". For most cases, this can be omitted; the type will be inferred based on the pin address number.	Inferred	no
mode	Number	See Modes	1 or 2 depending on type	no

Shape

Property Name	Description	Read Only
`id`	A user definable id value. Defaults to null	No
`pin`	The pin address of the pin	No
`type`	The type of pin this is, either "digital" or "analog"	No
`value`	The most recently reported value for this pin.	No
`mode`	The mode (number) for the pin. See "Modes" below	No

Component Initialization

Basic

// Digital
new five.Pin(13);

// Analog
new five.Pin("A0");

// Digital
new five.Pin({
  pin: 13
});

// Analog
new five.Pin({
  pin: "A0"
});

// Analog As Digital
new five.Pin({
  pin: 14,
  type: "digital"
});

Usage

var five = require("johnny-five");
var board = new five.Board();

board.on("ready", function() {
  var strobe = new five.Pin(13);
  var state = 0x00;

  this.loop(500, function() {
    strobe.write(state ^= 0x01);
  });
});

API

query(callback(value)) Query the board for the current state of this pin, invoking callback with argument state when complete.

var pin = new five.Pin(13);

pin.query(function(state) {
  console.log(state);
});

An example pin state object looks like:

{ 
  supportedModes: [ 0, 1, 3, 4 ],
  mode: 0,
  value: 0,
  report: 1,
  state: 1,
  analogChannel: 127 
}

Property	Description
`supportedModes`	This is a list of modes that are supported by the pin. These numbers correspond to the modes below.
`mode`	This is the present mode of the pin (eg. A digital output pin would have `mode: 1`).
`value`	This is the present value of the pin (eg. An analog pin with half voltage reading would have `value: 512`).
`report`	This pin is presently reporting its value.
`state`	For output modes, the `state` is any value that has been previously written to the pin. For input modes, the state is the status of the pullup resistor.
`analogChannel`	The numeric "index" of an analog (ADC) pin, or `127` if digital (eg. "A0" would have `analogChannel: 0`).

high() Set the pin HIGH.

var pin = new five.Pin(13);
// This will set pin 13 high (on)
pin.high();

low() Set the pin LOW.

var pin = new five.Pin(13);
// This will set pin 13 low (off)
pin.low();

write(value) Write a value to this pin.

var pin = new five.Pin(13);

pin.write(1);

read(callback(error, value)) Register a handler to be called whenever the board reports the value (digital or analog) of this pin.
```
var pin = new five.Pin(13);

pin.read(function(error, value) {
  console.log(value);
});
```

Events

Whenever a pin is set to INPUT or ANALOG, it will automatically emit the following events:

high The "high" event is emitted whenever the pin goes high.
low The "low" event is emitted whenever the pin goes low.
data The "data" event is emitted for every all data (firehose).

Static

Modes

Mode	Value	Constant
INPUT	0	Pin.INPUT
OUTPUT	1	Pin.OUTPUT
ANALOG	2	Pin.ANALOG
PWM	3	Pin.PWM
SERVO	4	Pin.SERVO

Methods

Pin.write(pin instance, value) Write a value to a pin.

// This will set pin 13 High
var pin = new five.Pin(13);

five.Pin.write(pin, 1);

Pin.read(pin instance, callback) Register a handler to be called whenever the board reports the value (digital or analog) of the specified pin.
```
var pin = new five.Pin(13);

five.Pin.read(pin, function(error, value) {
  console.log(value);
});
```