ViewSource

<!DOCTYPE html>
<html lang="ja">
<head>
<meta charset="utf-8">
<title>BLE write</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
</head>
<body>
<h1>BLE write</h1>
<p>Micro:bitに接続完了後、メッセージを送信してください。LEDにメッセージを表示します。</p>
<hr>
<p><button type="button" id="connect">接続</button> <span id="msg"></span></p>
<p><input id="send_text" value="hello"> <button type="button" id="send" disabled>送信</button></p>
<script>
var bluetoothDevice;
var characteristic;
 
var uuid1 = 'e95dd91d-251d-470a-a062-fa1922dfa9a8'; //LED_SERVICE_UUID
var uuid2 = 'e95d93ee-251d-470a-a062-fa1922dfa9a8'; //LED_TEXT_CHARACTERISTIC_UUID
//Micro:bitに接続する
document.getElementById('connect').addEventListener('click', function(e){
  if (document.getElementById('connect').textContent == '接続') {
    navigator.bluetooth.requestDevice({
      filters: [{namePrefix: 'BBC micro:bit'}],optionalServices: [uuid1]})
    .then(device => { bluetoothDevice = device; return device.gatt.connect(); })
    .then(server =>{ return server.getPrimaryService(uuid1); })
    .then(service => { return service.getCharacteristic(uuid2)  })
    .then(chara => { update(true) ; characteristic = chara; })  
    .catch(error => { msg.innerHTML = (error);  });   
  //BEL切断処理 
  } else { bluetoothDevice.gatt.disconnect() ; update(false) ; }
})
//LEDに表示するメッセージを送信
send.addEventListener('click', function(e) {
  characteristic.writeValue(new TextEncoder().encode(send_text.value + '\n'))
})
function update(connected) {
  connect.textContent = connected ? '切断' : '接続'
  msg.innerHTML = connected ? 'BLE connected' : 'BLE disconnected'
  send.disabled = !connected ;
}
</script>    
</body>
</html>