Bluetooth looses data at high speed

[EricHarbers]

Related area

BluetoothSerial.cpp driver (V2.0.14)

Hardware specification

ESP32 dev module

Is your feature request related to a problem?

On Arduino BSP I have created a program that reads data from the serial port and sends it to the Bluetooth SPP serial port. At high speeds (260 KBit/s) the bluetooth module looses data. If you connect to the Bluetooth SPP port using eg a PC with a client app, it will not receive all sent bytes.

Describe the solution you'd like

After searching around in my software, I concluded that the Bluetooth module would loose the data bytes.
Then I started looking around in the BluetoothSerial.cpp driver and found the initialisation of the Bluetooth Serial process. When I change the task priority of the Bluetooth Process, the problem is solved.

The change I have made is in the function "_init_bt()".
I changed this code:

if(!_spp_task_handle){
    xTaskCreatePinnedToCore(_spp_tx_task, "spp_tx", 4096, NULL, 10, &_spp_task_handle, 0);
    if(!_spp_task_handle){
        log_e("Network Event Task Start Failed!");
        return false;
    }
}

---

The changed code:

if(!_spp_task_handle){
    xTaskCreatePinnedToCore(_spp_tx_task, "spp_tx", 4096, NULL, configMAX_PRIORITIES-1, &_spp_task_handle, 0);
    if(!_spp_task_handle){
        log_e("Network Event Task Start Failed!");
        return false;
    }
}

---

I found this because other processes in the ESP32 module will have the (configMAX_PRIORITIES-1) priority.
After changing the priority, I have had no data loose at all.

Describe alternatives you've considered

In my code, I have made the transfer from serial port to SPP as fast as possible.
At first I transferred the data byte by byte. Now I transfer the data in blocks, using the read and write functions.
I 've looked around on the internet, but I couldn't find any good solution to my problem.
BluetoothSerial_changed.zip
ESP32_Myomed.zip

Additional context

No response

I have checked existing list of Feature requests and the Contribution Guide

• I confirm I have checked existing list of Feature requests and Contribution Guide.

[SuGlider]

@EricHarbers -Thanks for the report about this issue and the solution you have found.
It makes a lot of sense to change it to the highest possible priority, given that it is a Wireless interface and it may need to be on the high priority in order to achieve performance and throughput.

I'll add a PR to change it. Thanks!