# Multi strip example

This example uses johnny five to control multiple WS2812 strips using an I2C
backpack

To install the I2C backpack, see the [Installation Guide](installation.md).

## Wiring

Wire the neopixel strip up as shown below. This can be done on any I2C compatible
board that Johnny Five supports. This example uses a Raspberry Pi with 2 strips
attached to the backpack.

![Wiring diagram](breadboard/i2c_backpack_multipin_bb.png)

The example below uses two strips attached to the backpack connected to the host
Arduino Uno.

![Wiring diagram](breadboard/i2c_backpack_arduino_multipin_bb.png)

### I2C LED pins

Note that you can't specify the pins to use when using I2C. As such you must
start with pin 0 and work upwards from there to 8 max.

## Example code

```js
var five = require("johnny-five");
var pixel = require("node-pixel.js");

var opts = {};
opts.port = process.argv[2] || "";

var board = new five.Board(opts);
var strip = null;

var fps = 20; // how many frames per second do you want to try?

board.on("ready", function() {

    console.log("Board ready, lets add light");

    strip = new pixel.Strip({
        board: this,
        controller: "I2CBACKPACK",
        color_order: pixel.COLOR_ORDER.GRB,
        strips: [ 17,8 ]
    });

    strip.on("ready", function() {

        console.log("Strip ready");

        var colors = ["red", "green", "blue"];
        var current_colors = [0,1,2];
        var current_pos = [0,1,2];
        var blinker = setInterval(function() {

            strip.color("#000"); // blanks it out
            for (var i=0; i< current_pos.length; i++) {
                if (++current_pos[i] >= strip.stripLength()) {
                    current_pos[i] = 0;
                    if (++current_colors[i] >= colors.length) current_colors[i] = 0;
                }
                strip.pixel(current_pos[i]).color(colors[current_colors[i]]);
            }

            strip.show();
        }, 1000/fps);
    });

    strip.on("error", function(err) {
        console.log(err);
        process.exit();
    });
});
```

## Running

To run the example:

```
node examples/multipin-i2c.js
```

You can optionally pass a port in as a parameter.
