multipin-i2c.md

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.

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. For the Raspberry Pi to work with the backpack, include the raspi-io plugin to Johnny Five when initializing the Board.

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

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

var five = require("johnny-five");
var { Strip } = require("node-pixel-async");

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 = 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.length) {
                    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();
    });
});

When using a Raspberry Pi:

var Raspi = require("raspi-io");
var five = require("johnny-five");

const board = new five.Board({
    io: new Raspi()
});

// .. Rest of your code

Running

To run the example:

node examples/multipin-i2c.js

You can optionally pass a port in as a parameter.