Bangle.js 2

Bangle.js is the successor to Bangle.js, and is based on the SMA Q3.

Bangle.js 2 has now finished funding on KickStarter! If you'd like to be notified when you can order one, please enter your email address here

Development versions of Bangle.js 2 are now available in our shop

Bangle.js 2 is an open, hackable smartwatch

You can easily install new apps from the web or develop your own using JavaScript or a graphical programming language (Blockly). All you need is a Web Browser (Chrome, Edge or Opera) and you can upload apps or write code to run on your watch wirelessly! Bangle.js is waterproof and AI enabled and comes with Bluetooth Low Energy, GPS, a heart rate monitor, accelerometer and more.



Pre-release hardware

This is pre-release hardware at the moment and there are a few things you should be aware of:

Quick Usage Notes

There are a few things to know that'll really help you get started quickly:

Power Consumption

Right now you can expect around 1 month of battery life with a clock that updates once a minute, using the latest firmware.

A clock that updates once a second all the time (like s7clk) will reduce the battery life to 2 weeks, and more complicated clocks can increase the power draw further.


The supplied charge cable connects to a USB port to charge Bangle.js (despite there being 4 wires, those are for SWD programming and there is no USB data connection).

The cable is magnetic and the wires are connected directly to USB power. Do not leave your cable plugged in or it might attract itself to the nearest magnetic (probably conductive) object and short out.

Powering off


Apps are provided by the same Bangle.js app loader as for Bangle.js 1.

Right now compatible apps are tagged with b2 and incompatible apps are tagged with nbo2. You can use the link to see apps which are designed to work on Bangle.js 2.


If you the button too late you'll enter bootloader mode, in which case you need to wait for 30 seconds for the watch to automatically exit.

Resetting without loading any code

If you uploaded some code that runs at startup and breaks Bangle.js you may need to do this.

It won’t delete anything, so unless you fix/remove the broken code (see "Deleting all Code") Bangle.js will remain broken next time it restarts.

Deleting all code

You can do this either while your watch is in its normal state, or if you have reset it without loading any code (above).


This will erase everything and install just the default apps.


Deleting apps


In general, most tutorials related to Bangle.js 1 should work on Bangle.js 2, as long as you're aware that you only have one button and the screen resolution is different - see below under Information.

Upon release, specific Bangle.js 2 tutorials will be added here.

Tutorials using Bangle.js:

Tutorials using Bluetooth LE:

Tutorials using Bluetooth LE and functionality that may not be part of Bangle.js:

There are many more tutorials that may not be specifically for you device but will probably work with some tweaking. Try searching to find what you want.


LCD Screen

Bangle.js displays the REPL (JavaScript console) if Debug Info: show has been set in settings. If enabled, any calls like print("Hello") or console.log("World") will output to the LCD when there is no computer connected via Bluetooth. Any errors generated when there is no connection will also be displayed on the LCD.


You can output graphics on Bangle.js's display via the global variable g that is an instance of the Graphics class. Unlike Bangle.js 1, the display is buffered so changes to the display will only take effect when you call g.flip() or your code finishes executing and Bangle.js returns to idle.

// Draw a pattern with lines
for (i=0;i<64;i+=7.9) g.drawLine(0,i,i,63);
g.drawString("Hello World",30,30);

Bangle.js comes with a built-in menu library that can be accessed with the E.showMenu() command.

E.showPrompt() and E.showMessage() can also be used for simple prompts and full-screen messages.

// Two variables to update
var boolean = false;
var number = 50;
// First menu
var mainmenu = {
  "" : {
    "title" : "-- Main Menu --"
  "Beep" : function() { Bangle.beep(); },
  "Buzz" : function() {; },
  "Submenu" : function() { E.showMenu(submenu); },
  "A Boolean" : {
    value : boolean,
    format : v => v?"On":"Off",
    onchange : v => { boolean=v; }
  "A Number" : {
    value : number,
    onchange : v => { number=v; }
  "Exit" : function() { E.showMenu(); },
// Submenu
var submenu = {
  "" : {
    "title" : "-- SubMenu --"
  "One" : undefined, // do nothing
  "Two" : undefined, // do nothing
  "< Back" : function() { E.showMenu(mainmenu); },
// Actually display the menu

See for more detailed information.


Bangle.js's LCD acts as a VT100 Terminal. To write text to the LCD regardless of connection state you can use Terminal.println("your text"). Scrolling and simple VT100 control characters will be honoured.

You can even move the JavaScript console (REPL) to the LCD while connected via Bluetooth, and use your bluetooth connection as a simple keyboard using the following commands:


On-device Peripherals

Most peripherals on the device are accessible via fields and events on the Bangle object.


Bangle.js 2 has a full touchscreen.

Bangle.on('touch', function(zone,e) { ... }); will call the function with e as an object containing {x,y} every time the screen is tapped (when unlocked).

Bangle.on('drag', function(e) { ... }); will call the function with e as an object containing {x,y,dx,dy,b} whenever a finger is dragged over the screen. b is 0 when the finger is lifted or 1 when pressed.


There are two 'fake' LED variables called LED1 and LED2 that create red and green fake LEDs at the top of the watch screen - these serve no purpose other than to allow tutorials for existing Espruino boards to be used.

If you want to control the backlight LED use Bangle.setLCDBrightness.

Vibrate will make Bangle.js's vibration motor turn on. It takes optional time and strength arguments, and returns a promise. See the reference.

For example:>{
  return new Promise(resolve=>setTimeout(resolve,500)); // wait 500ms

Will do a short buzz followed by a long buzz and will print Done when finished.


You can use Bangle.beep() in much the same way as .buzz above to make sounds. See the reference.

To output an entire scale of notes, you could do:


Note: Bangle.js 2 does not contain a piezo speaker, but instead uses the vibration motor for sound. This means that while you can get some sound, it is extremely weak.


There is just one button on Bangle.js - called BTN or BTN1 in code.

setWatch(function() {
}, BTN, {edge:"rising", debounce:50, repeat:true});


The accelerometer runs all the time and produces accel events on the Bangle object.

Bangle.on('accel', function(acc) {
  // acc = {x,y,z,diff,mag}

See the reference for more information.


When a sudden movement is detected, the accelerations in it are recorded and a gesture event is created.

If .tfmodel and .tfnames files are created in storage, Tensorflow AI will be run on the model with the gesture information and an aiGesture event will be created with the name of the detected gesture.


The compass can be turned on with Bangle.setCompassPower(1) and when enabled, mag events are created 12.5 times a second:

Bangle.on('mag', function(mag) {
  // mag = {x,y,z,dx,dy,dz,heading}

See the reference for more information.

Barometer / air pressure sensor

To use the barometer, you can either request one pressure value:

// prints this after ~1 sec
// { "temperature": 23.03918464465, "pressure": 1005.56287398937, "altitude": 64.19805781010 }

Or can request to be notified on each new reading:

Bangle.on('pressure', print)
// prints...
{ "temperature": 23.14690527655, "pressure": 1005.79911673786, "altitude": 62.21919777595 }
{ "temperature": 23.14200888113, "pressure": 1005.84599901953, "altitude": 61.82653852506 }
{ "temperature": 23.14200888113, "pressure": 1005.79091150423, "altitude": 62.28792165657 }
{ "temperature": 23.14690527655, "pressure": 1005.79911673786, "altitude": 62.21919777595 }

See the reference for more information.


The GPS can be turned on with Bangle.setGPSPower(1) and when enabled, GPS events are created once a second:

Bangle.on('GPS', function(gps) {
  // gps = {lat,lon,alt,speed,etc}

GPS-raw events are also created containing a String for each NMEA line that comes from the GPS receiver. These contain far more detailed information from the GPS.

See the reference for more information.

Hardware SWD

Bangle.js 2 has the hardware SWD pin brought out on the back of the watch along with the charging pins:

This can be connected to an SWD programmer. We'd recommend using an nRF52 DK (or nRF52840DK). When using the nRF52DK you'll need to short the GND DETECT pin to GND to tell it you're programming the Bangle.js and not the on-board nRF52.

The easiest way to connect to these is to use the provided USB charge cable and to wire up a USB type A socket:

Pin # Connect
1 5v (not required)

Firmware Updates

Note: It is also possible to use the Web IDE to update Bangle.js firmware. Click Settings (top right), then Flasher and follow the instructions.


Check out:

Other Official Espruino Boards

This page is auto-generated from GitHub. If you see any mistakes or have suggestions, please let us know.