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Launchpad.js

Interact with your launchpads in Node.js

Launchpad running an example script

Launchpad displaying a cross

This project started as a module for my own stream system to make several things interact with OBS studio, named rewards-interaction. After re-writing a broken launchpad library I decided to release the library to the public so everyone can enjoy easy programming on their launchpad.

Some sample programs can be found in the examples folder.

Launchpad models currently supported

  • Launchpad MK1 (limited support)
  • Launchpad MK2
  • Launchpad MK3 (only tested with Mini)

Dummy launchpad

This library contains a DummyLaunchpad class. This can be used to test calls even if you don't have a launchpad attached/

Why are only these launchpads supported?

These launchpads are supported because I own them myself and have been able to test them. If a launchpad is not listed here it means that I do not own one and have not been able to test that one with the program.

Installation

Install from NPM using npm i launchpad.js and make sure you have drivers installed for your device.

Examples

More examples can be found in the examples folder, this is just a simple button listener.

const { autoDetect, colors } = require('launchpad.js');
const { colorFromHex, defaultColors } = colors;

const lp = autoDetect();

// Alternatively:
//
//    await waitForReady(lp);

lp.once('ready', (deviceName) => {
  console.log(`${deviceName} is ready!!`);

  lp.on('buttonDown', (button) => {
    // Generate a random color on each button press
    const randHex = Math.floor(Math.random() * 16777215).toString(16);

    // The Launchpad accepts an RGB-triple between 0 and 1. This converts the
    // hex code to the appropriate number array.
    const color = colorFromHex(randHex);

    console.log(`Button pressed ${button.nr} (x: ${button.xy[0]}, y: ${button.xy[1]}`);

    lp.setButtonColor(button, color);
  });

  lp.on('buttonUp', (button) => {
    lp.setButtonColor(button, defaultColors.off);
  });
});

Low-level API

A number of methods are available to control the button colors on the LaunchPad. In all of these methods, the button to control can be specified in one of the following ways:

  • number, indicating a Launchpad-specific button number
  • [x, y], a Launchpad-independent button coordinate with (0, 0) in the top-left.
  • Button, a Button object (as returned by the buttonDown or buttonUp event handlers).

The follow methods control a button's color:

  • lp.setButtonColor(button, colorOrRGB): set a button to a solid color. colorOrRGB is either:
    • number between 0..127, a color in the 128-color palette of the Launchpad.
    • [r, g, b], an array of RGB values between 0 and 1.
  • lp.flash(button, color, colorB?): flash a button between two palette colors. For colors that don't support a second color, the button will flash to black.
  • lp.pulse(button, color): a button will pulse between black and the given palette color.

Surface API

There is also a buffer-oriented API you can use, which works much like how graphics cards work. The class Surface addresses the Launchpad grid as one or more layers of 9x9 buttons. You can set and get the individual button styles, and call update() to send all changes to the Launchpad.

A helper class Drawing exists to help with performing common drawing operations.

See the examples/surface.js example for more information on how to use this API.

Limited support for the legacy Launchpad MK1

Launchpad MK1 offers less functionality over newer models and therefore has some limitations. As a result of the implementation for the MK1 being retro-fitted into this package, that has been designed to work with more advanced models, the API for MK1 isn't fully compatible with that of newer models. The differences are specified in this section.

Colors

Buttons on Launchpad MK1 only have two LEDs, red and green, that can output four intensities each:

  • 0 off.
  • 1 low brightness.
  • 2 medium brightness.
  • 3 full brightness.

This means the MK1 can only display a few different colors and that RgColor and RgbColor values (in range 0..1) consumed by methods like lp.setButtonColor(), lp.flash() and lp.pulse() are converted to either one of the four color intensities. See type RgColor for more information on this conversion.

Because there is no blue LED, methods that consume an RgbColor value also accept RgColor values.

Color palette

The Launchpad MK1 doesn't have a color palette. Methods that consume a PaletteColor may instead accept a Velocity value (specific to MK1). See method lp.velocity() and type Velocity for more information.

Methods that exclusively consume PaletteColors on newer models (being lp.flash() and lp.pulse()) instead accept an RgColor, RgbColor or Velocity value on Launchpad MK1.

Method lp.setButtons() uses different styles (Mk1ButtonStyle and Mk1Style) due to color palettes not being available, see type Mk1Style for more information.

Flashing buttons

Buttons on Launchpad MK1 can only pulse between off and a specified color, it does not support flashing between two specified colors. This results in method lp.flash() only accepting one color argument and thus providing the exact same signature and functionality as lp.pulse().

TODO

  • Add support for the same launchpads as launchpad.py

Related resources

More recent versions of programmers references may be available on Novation Music's website.

Notice

This project contains modified code from https://github.com/Lokua/launchpad which was released under the MIT license.