Sending Text to Micro:Bit

Menu showing devices

We're going to use a Pixl.js board with Espruino to scan for Micro:bit devices programmed with MakeCode and to then send text to them using the UART service.

Micro:Bit software

  • Go to MakeCode and ensure you're in Blocks mode up the top.
  • Under the Advanced heading click Add Package (you may have to expand Advanced first)

Add Package

  • Type Bluetooth and click on the Bluetooth package

Bluetooth Package

  • Click Yes to the dialog telling you that radio functions won't be available.

Bluetooth Package Warning

  • Click the Settings icon in the top right, and click Project Settings
  • Ensure that the No Pairing Required slider is set to On, and click Save

No Pairing Required

  • Pull in an on start block from Basic
  • Click Bluetooth, then ... More, and pull a bluetooth uart service block into on start
  • Pull show icon from Basic into the end of on start as well - it'll show that everything is working

  • Now pull in a forever block from Basic

  • Pull show string from Basic and put it in forever
  • Click Bluetooth, then ... More, and pull a bluetooth red until newline block into the show string block

Your code should look like this:

Finished code

Click Download and save the file to each Micro:bit you're interested in.

Pixl.js Software

On the Pixl, we'll write code that scans for any Micro:Bits (with names beginning with BBC) and displays them in a menu. When chosen from a menu you have a choice of text to send, and then a connection will be made and the text will be sent.

For Pixl.js, follow the Getting Started Guide to get connected with the Espruino IDE.

Copy and paste the following code to the right-hand side of the IDE and click Upload, and you're done!

// Do a scan and display the results in a menu
function doScan() {; // remove menu
  NRF.findDevices(function(devs) {
    var menu = { "" : {title:"No Devices Found"} };
    // Add any device with a name beginning with 'BBC'
    devs.forEach(function(dev) {
      if ( &&,3)=="BBC") {
        found = true;
        menu[""].title = "-- Connect -- ";
        menu[] = function() {
    // Add a menu option to rescan
    menu["-> Scan Again"] = function() {
      doScan(); // scan
    // Show the menu;

// Show a list of text to send to the micro:bit
function askForText(dev) {{
    "":{title:"Which text?"},
    "Hello":function() { doConnect(dev,"Hello\n"); },
    "Goodbye":function() { doConnect(dev,"Goodbye\n"); },
    "A Test":function() { doConnect(dev,"A Test\n"); },
    "-> Scan Again":function() { doScan(); },

/* Connect and send, max 20 characters. The micro:bit's
UART isn't actually a standard Nordic UART so we can't
use built-in libraries and have to do this manually. */
function doConnect(dev, text) {; // remove menu
  var device;
  dev.gatt.connect().then(function(d) {
    Terminal.println("Connected! Finding service");
    device = d;
    return d.getPrimaryService("6e400001-b5a3-f393-e0a9-e50e24dcca9e");
  }).then(function(s) {
    Terminal.println("Finding characteristic");
    return s.getCharacteristic("6e400003-b5a3-f393-e0a9-e50e24dcca9e");
  }).then(function(c) {
    return c.writeValue(text);
  }).then(function() {
    setTimeout(function() {
    }, 2000);
  }).catch(function(err) {
    setTimeout(function() {
    }, 2000);
    if (device) device.disconnect();

// When initialised start scanning
function onInit() {


Type save() to write this code to Pixl.js so it'll be run automatically even after power is removed and restored.

Menu showing devices

More functionality

You can now send any text to a Micro:bit, so you could write code on the Micro:bit that checked if the text was a command and that did what it said - for instance "forward" might move a Micro:bit Robot forwards.

Responding to commands

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