Unable to receive micro: bit uartWriteString with startNotifications

[marron9999]

Expected Behavior

Hope to be able to receive with _onMessage (base64)

Actual Behavior

_onMessage (base64) is not called

Steps to Reproduce

const BLEUUID = {
service: '6e400001-b5a3-f393-e0a9-e50e24dcca9e', // UART_SERVICE
rxChar: '6e400002-b5a3-f393-e0a9-e50e24dcca9e', // TX_Characteristic
txChar: '6e400003-b5a3-f393-e0a9-e50e24dcca9e' // RX_Characteristic
};

this._ble.read(BLEUUID.service, BLEUUID.rxChar, true, this._onMessage);

Operating System and Browser

Windows 10 Home 20H2 (19042.867)
Google Chrome 89.0.4389.90（Official Build）(64 bit）

NOTE:

Bluetooth Developer Studio Level 3 Profile Report
TX Characteristic
Notify Excluded
Indicate Mandatory

scratch-link/Windows/scratch-link/BLESession.cs
private async Task StartNotifications(GattCharacteristic endpoint, string encoding)

            var notificationRequestResult = await endpoint.WriteClientCharacteristicConfigurationDescriptorAsync(
                    GattClientCharacteristicConfigurationDescriptorValue.Notify);

Can be received by changing "Notify" to "Indicate"

[BryceLTaylor]

Can a user only experience this with a custom extension?

[marron9999]

Yes. I made another extension. It is scratch-microbit extension with the UUID changed to UART.
OK: this._ble.write(BLEUUID.service, BLEUUID.txChar, data, "base64", true)
NG: this._ble.read(BLEUUID.service, BLEUUID.rxChar, true, this._onMessage)
　　　=> this._onMessage is not called.
I want you to be able to with "Notify" and "Indicate".

[eqot]

rxChar and txChar are different from the comments.

rxChar: '6e400002-b5a3-f393-e0a9-e50e24dcca9e', // TX_Characteristic
txChar: '6e400003-b5a3-f393-e0a9-e50e24dcca9e' // RX_Characteristic

Are these correct?

[marron9999]

Yes, please see code of scratch extension

https://github.com/marron9999/sc3-mbitlink/blob/master/scratch-vm/src/extensions/scratch3_mbitlink/index.js

const BLEUUID = {
service: '6e400001-b5a3-f393-e0a9-e50e24dcca9e', // UART_SERVICE
rxChar: '6e400002-b5a3-f393-e0a9-e50e24dcca9e', // TX_Characteristic
txChar: '6e400003-b5a3-f393-e0a9-e50e24dcca9e' // RX_Characteristic
};

this._ble.read(BLEUUID.service, BLEUUID.rxChar, true, this._onMessage)
this._ble.write(BLEUUID.service, BLEUUID.txChar, data, "base64", true)

scratch-vm/src/io/BLE.js

read (serviceId, characteristicId, optStartNotifications = false, onCharacteristicChanged = null) {
const params = {
serviceId,
characteristicId
};
if (optStartNotifications) {
params.startNotifications = true;
}
if (onCharacteristicChanged) {
this._characteristicDidChangeCallback = onCharacteristicChanged;
}
return this.sendRemoteRequest('read', params)
.catch(e => {
this.handleDisconnectError(e);
});
}

write (serviceId, characteristicId, message, encoding = null, withResponse = null) {
const params = {serviceId, characteristicId, message};
if (encoding) {
params.encoding = encoding;
}
if (withResponse !== null) {
params.withResponse = withResponse;
}
return this.sendRemoteRequest('write', params)
.catch(e => {
this.handleDisconnectError(e);
});
}