For another device like a smartphone to use any of the Bluetooth “services” which the micro:bit has, it must first be paired with the micro:bit. Once paired, the other device may connect to the micro:bit and exchange data relating to many of the micro:bit’s features.
This block starts an event handler which in this case will run when a device which is connected to your micro:bit over Bluetooth disconnects.
You could use this event handler to display a letter “D” on the micro:bit LED grid so you know that the Bluetooth connection has been closed.
bluetooth.onBluetoothDisconnected(() => {
});bluetooth.onBluetoothDisconnected(() => {
basic.showString("D");
});About Bluetooth, micro:bit Bluetooth profile overview , micro:bit Bluetooth profile reference, Bluetooth on micro:bit resources, Bluetooth SIG
bluetooth