🛠 Se connecter en BLE UART depuis un smartphone

Objectives

Expose a BLE "UART" service (serial profile) from the micro:bit V2 to send and receive text with a smartphone or PC, without a cable. Since the MicroPython radio module does not expose a serial GATT profile, we use MakeCode and its Bluetooth extension here.

Hardware

• 1 micro:bit V2 board
• 1 Android/iOS smartphone with a "micro:bit" or "Bluetooth Terminal" application
• Editor makecode.microbit.org (Bluetooth extension to be added)

Complete code

// MakeCode (JavaScript) — ajouter l'extension "Bluetooth"
// Profil Bluetooth: UART (réglage de l'extension)

let trame = ""

bluetooth.onBluetoothConnected(function  {
    basic.showString("BLE")
})

bluetooth.onUartDataReceived(serial.delimiters(Delimiters.NewLine),
    function  {
        trame = bluetooth.uartReadUntil(serial.delimiters(Delimiters.NewLine))
        if (trame === "ROUGE") {
            basic.showString("R")
        } else if (trame === "COEUR") {
            basic.showIcon(IconNames.HEART)
        } else {
            basic.showString(trame)
        }
    })

basic.forever(function  {
    if (input.buttonIsPressed(Button.A)) {
        bluetooth.uartWriteString("BOUTON A APPUYE\n")
        basic.pause(500)
    }
})

The micro:bit remains in BLE (SoftDevice S113): no Wi-Fi or Ethernet on this board. In MicroPython, the closest equivalent remains the radio module, which is not a standard GATT UART profile.

Expected verification

The application finds a "BBC micro:bit" device, connects, then: typing "HEART" + enter displays a heart on the matrix; pressing A sends "BUTTON A PRESSED" to the phone.

Common errors

• Bluetooth extension not added in MakeCode: the bluetooth.* blocks do not exist.
• Forgetting the newline delimiter in the terminal: the frame is never "received complete".
• Classic pairing fails: this BLE profile often does not use a PIN code, connect from the application side.
• The radio or BLE program is already occupied: only one connection at a time, disconnect the other app.