Web Bluetooth with micro:bit (UART)

script.js

// https://lancaster-university.github.io/microbit-docs/resources/bluetooth/bluetooth_profile.html
// An implementation of Nordic Semicondutor's UART/Serial Port Emulation over Bluetooth low energy
const UART_SERVICE_UUID = "6e400001-b5a3-f393-e0a9-e50e24dcca9e";

// Allows the micro:bit to transmit a byte array
const UART_TX_CHARACTERISTIC_UUID = "6e400002-b5a3-f393-e0a9-e50e24dcca9e";

// Allows a connected client to send a byte array
const UART_RX_CHARACTERISTIC_UUID = "6e400003-b5a3-f393-e0a9-e50e24dcca9e";

let uBitDevice;
let rxCharacteristic;

function setup() {
  createCanvas(200, 200);

  const connectButton = createButton("Connect");
  connectButton.mousePressed(connectButtonPressed);

  const disconnectButton = createButton("Disconnect");
  disconnectButton.mousePressed(disconnectButtonPressed);

  const pingButton = createButton("Ping");
  pingButton.mousePressed(pingButtonPressed);
}

function draw() {
  background(0);
}

async function connectButtonPressed() {
  try {
    console.log("Requesting Bluetooth Device...");
    uBitDevice = await navigator.bluetooth.requestDevice({
      filters: [{ namePrefix: "BBC micro:bit" }],
      optionalServices: [UART_SERVICE_UUID]
    });

    console.log("Connecting to GATT Server...");
    const server = await uBitDevice.gatt.connect();

    console.log("Getting Service...");
    const service = await server.getPrimaryService(UART_SERVICE_UUID);

    console.log("Getting Characteristics...");
    const txCharacteristic = await service.getCharacteristic(
      UART_TX_CHARACTERISTIC_UUID
    );
    txCharacteristic.startNotifications();
    txCharacteristic.addEventListener(
      "characteristicvaluechanged",
      onTxCharacteristicValueChanged
    );
    rxCharacteristic = await service.getCharacteristic(
      UART_RX_CHARACTERISTIC_UUID
    );
  } catch (error) {
    console.log(error);
  }
}

function disconnectButtonPressed() {
  if (!uBitDevice) {
    return;
  }

  if (uBitDevice.gatt.connected) {
    uBitDevice.gatt.disconnect();
    console.log("Disconnected");
  }
}

async function pingButtonPressed() {
  if (!rxCharacteristic) {
    return;
  }

  try {
    let encoder = new TextEncoder();
    rxCharacteristic.writeValue(encoder.encode("P\n"));
  } catch (error) {
    console.log(error);
  }
}

function onTxCharacteristicValueChanged(event) {
  let receivedData = [];
  for (var i = 0; i < event.target.value.byteLength; i++) {
    receivedData[i] = event.target.value.getUint8(i);
  }

  const receivedString = String.fromCharCode.apply(null, receivedData);
  console.log(receivedString);
  if (receivedString === "S") {
    console.log("Shaken!");
  }
}

scripts

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web-bluetooth-with-micro-bit-uart.markdown

Web Bluetooth with micro:bit (UART)

This is a demo that illustrates a way to connect a micro:bit and a PC running the Chome web browser using the Web Bluetooth API and send/receive strings using the UART service .

You can get the code for micro:bit at https://makecode.microbit.org/_C06XuChrjRvs

Note: You have to open this Pen in the Debug Mode, since the Web Bluetooth doesn't work on cross-origin iframes.

WebBluetoothCG/web-bluetooth#180 https://bugs.chromium.org/p/chromium/issues/detail?id=518042&desc=2

A Pen by Shigeru Kobayashi on CodePen.

License.