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.

The Bluetooth UART service allows another device such as a smartphone to exchange any data it wants to with the micro:bit, in small chunks.

With the Bluetooth UART service running, this block allows a micro:bit to read data which has been received from a Bluetooth connected device, terminating reading and returning the value obtained as soon as a specified delimiter character is encountered. This means that connected devices can send data to the micro:bit and indicate that the complete message has been sent by appending the message with the delimiter character.


Example: Starting the Bluetooth UART service and then reading data received from another device which is terminated by “:” character and then displaying it

let uartData = "";
let connected = 0;
bluetooth.onBluetoothConnected(() => {
    connected = 1;
    while (connected == 1) {
        uartData = bluetooth.uartReadUntil(":");
bluetooth.onBluetoothDisconnected(() => {

Video - UART service guessing game


For more advanced information on the micro:bit Bluetooth UART service including information on using a smartphone, see the Lancaster University micro:bit runtime technical documentation

See also

About Bluetooth, micro:bit Bluetooth profile overview , micro:bit Bluetooth profile reference, Bluetooth on micro:bit resources, Bluetooth SIG