Sending Text to Micro:Bit

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)

• Type Bluetooth and click on the Bluetooth package

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

• 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

• 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:

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() {
  Pixl.menu(); // remove menu
  Terminal.println("Scanning...");
  NRF.findDevices(function(devs) {
    var menu = { "" : {title:"No Devices Found"} };
    // Add any device with a name beginning with 'BBC'
    devs.forEach(function(dev) {
      if (dev.name && dev.name.substr(0,3)=="BBC") {
        found = true;
        menu[""].title = "-- Connect -- ";
        menu[dev.name] = function() {
          askForText(dev);
        };
      }
    });
    // Add a menu option to rescan
    menu["-> Scan Again"] = function() {
      doScan(); // scan
    };
    // Show the menu
    Pixl.menu(menu);
  });
}

// Show a list of text to send to the micro:bit
function askForText(dev) {  
  Pixl.menu({
    "":{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) {
  Pixl.menu(); // remove menu
  Terminal.println("Connecting...");
  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) {
    Terminal.println("Sending");
    return c.writeValue(text);
  }).then(function() {
    device.disconnect();
    Terminal.println('Done!');
    setTimeout(function() {
      doScan();
    }, 2000);
  }).catch(function(err) {
    print(err);    
    Terminal.println("Error!");
    setTimeout(function() {
      doScan();
    }, 2000);
    if (device) device.disconnect();
  });
}

// When initialised start scanning
function onInit() {
  doScan();
}

onInit();

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

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.