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node-piglow

★ 37 Open GitHub ↗

javascript interface for the piglow

// repository documentation

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# node-piglow [![Build Status](https://travis-ci.org/seriousManual/node-piglow.png)](https://travis-ci.org/seriousManual/node-piglow)

**v2 does not contain the commandline interface and the animations interface anymore. They are moved to two seperate modules. ([node-piglow-cli](https://github.com/zaphod1984/node-piglow-cli) and [node-piglow-animations](https://github.com/zaphod1984/node-piglow-animations))**

**v3 removes node 0.10 and 0.12 support and only works for node versions >4**

[![NPM](https://nodei.co/npm/piglow.png)](https://nodei.co/npm/piglow/)

[![NPM](https://nodei.co/npm-dl/piglow.png?months=3)](https://nodei.co/npm/piglow/)

The piGlow is a little LED-Board for the [Raspberry Pi](http://www.raspberrypi.org/) sold by [Pimoroni](http://shop.pimoroni.com/products/piglow). It features 18 LEDs in six different colors (white, blue, green, yellow, orange, red) arranged like a vortex:

This module offers an interface to control the individual LEDs.

In action video:
http://www.youtube.com/watch?v=s-rD8PfAke8

## TOC

* [Installation](#installation)
* [Setup](#setup)
* [Invocation](#invocation)
* [Adressing](#adressing)
* [Transactions](#transactions)
* [Animations](#animations)
* [CLI](#command-line-interface)
* [Mocking](#mocking)
* [Used in](#used-in)

## Installation

````bash
$ npm install piglow
````

## Setup

````bash
$ sudo vi /etc/modules
````

Add these two lines

````bash
i2c-bcm2708 
i2c-dev
````

````bash
$ sudo vi /etc/modprobe.d/raspi-blacklist.conf
````

Comment out blacklist i2c-bcm2708

````
#blacklist i2c-bcm2708
````

## Invocation

```javascript
var piGlow = require('piglow');

//callback fires when board is initialized
piGlow(function(error, pi) {
    pi.all;
});

```

## Adressing

To each LED a brightness value between 0 (off) and 255 (freakin' bright) can be assigned.
If one preferrs percentage values, as a convenience function all values smaller than 1 are treated as percentage values. Note that the value of '1' is not treated as 100% but as the brightness value of 1!

### Individual LEDs
```javascript
//parameter sets the brightness:
pi.l_0_0 = 100; //sets LED 1 of leg 1 to a brightness of 100 (of 255)
pi.l_0_1 = 10; //sets LED 2 of leg 1 to a brightness of 10
pi.l_0_1 = 0.5; //sets LED 2 of leg 1 to a brightness of 50% (=brightness of 127)
...
pi.l_2_5 = 200; //sets LED 6 of leg 3 to a brightness of 200

//shorthand form:
pi.l_0_0; //sets LED 1 of leg 1 to a brightness of 255
```

### Legs
```javascript
pi.leg_0 = 100; //sets all LEDs of leg 1 to a brightness of 100

//shorthand
pi.leg_0; //sets all LEDs of leg 1 to 255
```

### Rings
```javascript
pi.ring_0 = 100; //sets LED 1 of leg 1, LED 1 of leg 2 and LED 1 of leg 3 to 100

//shorthand
pi.ring_0; //sets LED 1 of leg 1, LED 1 of leg 1 and LED 1 of leg 2 to 255
```

As the rings are distinguishable by color (order from outer ring to the inner: red, orange, yellow, green, blue, white), they can be adressed via the ring's color:
```javascript
pi.red = 100; //sets the first ring to a brightness of 100

//shorthand
pi.red; //sets the first ring to maximum brightness
```

### All LEDs
```javascript
pi.all = 100; //set all LEDs to 100

//shorthand
pi.all; //set all LEDs to 255 (watch your eyes)

pi.reset; //set all LEDs to 0
```

### Random
```javascript
pi.random = 0.5;

//shorthand
pi.random;
```
The propbability of lighting up can be defined (`pi.random = 0.1;`) and is otherwise calculated via this formula: `(0.4 + Math.random() * 0.2);`.
The brightness is calculated via this formula: `parseInt(MAX_VALUE / 2 + (MAX_VALUE / 2 * Math.random()), 10)`

## Transactions

Each parameter that is set causes the backend to transfer the complete set of values to the piglow board.
Thus the following operation would cause three write operations:

```javascript
pi.l_0_1 = 100;
pi.l_0_2 = 100;
pi.l_0_3 = 100;
```

The piglow-interface offers the possibility to open up a transaction and to commit it when all changes have been made. So the following code will cause only one write to the hardware board:

```javascript
pi.startTransaction();
pi.l_0_1 = 100;
pi.l_0_2 = 100;
pi.l_0_3 = 100;
pi.commitTransaction();
```

This benefits performance especially when the LEDs are changed in high frequency.

## Animations

Do you like your piglow animated? Checkout [piglow-animations](https://www.npmjs.org/package/piglow-animations)!

 <img src="https://raw.githubusercontent.com/zaphod1984/node-piglow-animations/master/pics/animation.gif" />

## Command-Line-Interface

[node-piglow-cli](https://www.npmjs.org/package/piglow-cli) wraps piglow and offers a command line interface. You can than invoke the piglow like this (lights up the red LEDs):
```bash
$ piglow --red
```

Possible use cases:
* use it in your Makefile to indicate a sucessfull built
* use it in your CI server to indicate failed (or sucessfull) built
* ...

## Mocking

This module also exposes its internal structure, with the possibility to invoke the piGlow interface with a injected mocking backend.
There are two backends, `BackendMock` prints the piglow data as JSON, `BackendMockPrettyPrint` structures the data in a readable way.
```javascript
var piGlow = require('piglow');
var PiGlowBackendMock = piGlow.BackendMock;
var piGlowInterface = piGLow.piGlowInterface;

var myMock = new PiGlowBackendMock();
var myInterface = piGlowInterface(myMock);

//lets hack
myInterface.ring_0 = 255;
```

This way the module can be used in a non raspi environment for development or with a testing mock for unit tests.
To implement your own mocks follow this interface:
```javascript
function PiGlowMock() {}

PiGlowMock.prototype.update = function(piGlowConfiguration, callback) {
  /*
    piGlowConfiguration is a object in the following form:
    {
        "l_0_0":0, "l_0_1":0, "l_0_2":0, "l_0_3":0, "l_0_4":0, "l_0_5":0,
        "l_1_0":0, "l_1_1":0, "l_1_2":0, "l_1_3":0, "l_1_4":0, "l_1_5":0,
        "l_2_0":0, "l_2_1":0, "l_2_2":0, "l_2_3":0, "l_2_4":0, "l_2_5":0
    }
  */
};
```

## Used in
- *[piglow-system](https://www.npmjs.com/package/piglow-system)*
  a system utlity tool that shows metrics about your system 
- *[piglow-clock](https://www.npmjs.com/package/piglow-clock)*
  a binary watch implemented via the piglow

node-piglow

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