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raspi-rotary-encoder

Raspi Rotary Encoder

Add Rotary Encoders to your Raspberry Pi with ease!

Rotary Encoder is inspired by, and designed to work with @nebrius' Raspi.js suite. This README is heavily based on those tools.

If you have a bug report, feature request, or wish to contribute code, please be sure to check out the Contributing Guide.

Installation

Install raspi as this library uses that to set-up the Pi and configure the GPIO pins.

Install raspi-rotary-encoder with NPM:

npm install raspi-rotary-encoder

Warning: this module's dependencies require GCC 4.8 or newer. This means that you should be running Raspbian Jessie or newer, released in September of 2015.

Example Usage

var raspi = require('raspi');
var RotaryEncoder = require('raspi-rotary-encoder').RotaryEncoder;
 
raspi.init(function() {
  var encoder = new RotaryEncoder({
    pins: { a: 5, b: 4 },
    pullResistors: { a: "up", b: "up" }
  });
 
  encoder.addListener('change', function (evt) {
    console.log('Count', evt.value);
  })
});

Pin Naming

The pins on the Raspberry Pi are a little complicated. There are multiple headers on some Raspberry Pis with extra pins, and the pin numbers are not consistent between Raspberry Pi board versions.

To help make it easier, you can specify pins in three ways. The first is to specify the pin by function, e.g. 'GPIO18'. The second way is to specify by pin number, which is specified in the form "P[header]-[pin]", e.g. 'P1-7'. The final way is specify the Wiring Pi virtual pin number, e.g. 7. If you specify a number instead of a string, it is assumed to be a Wiring Pi number.

API

new RotaryEncoder(config)

Instantiates a new RotaryEncoder instance using the config object properties:

Arguments:

Property Type Description
pins Object ```{ a, b }```. Object of the pins to use for the encoder's A and B pins. The values for ```a``` and ```b``` can be a number or string as described in "Pin naming" above.
Property Type Description
a Number | String The pin number connected to the A leg of the encoder
b Number | String The pin number connected to the B leg of the encoder
pullResistors Object (optional) ```{ a, b }```. Object of the pull-up or pull-down resistors to use (if any) for the encoder's A and B pins.
Property Type Description
a String The strings ```up```, ```down``` or ```none``` are valid.
b String The strings ```up```, ```down``` or ```none``` are valid.

Instance Properties

None

Instance Methods

addListener(eventName, callback)

Register an event listener function callback

Arguments:

Argument Type Description
eventName String A valid event name (see Events below)
callback Function A function to be called whenever the event occurs

Returns: A reference to this encoder instance

removeListener(eventName, callback)

Unregister an event listener function callback

Arguments:

Argument Type Description
eventName String A valid event name (see Events below)
callback Function A listener function that was previously registered with addListener

Returns: A reference to this encoder instance

Events

Use addListener to listen for events. Listener callback functions will be passed an event object containing information about the event.

Event name Description
change Fires when the rotary encoder is turned in either direction. The listener is passed a single object with the following property:
Property Type Description
value Number An ever-increasing or decreasing number. Positive numbers indicate clockwise, negative indicate anticlockwise. These do not correspond to a full-rotation of the encoder.

License

The MIT License (MIT)

Copyright (c) 2016 Andrew Nicolaou me@andrewnicolaou.co.uk

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.