Nordic UART not working on ESP32-C6

[ondrejkarpis]

I tried basic BLE UART example with ESP32-C6-DevKitC-1 and it doesn't work. When I use a BLE scan app, it is not able to discover any UART service (just the Generic Access 1800, Generic Attribute 1801, and Service FFE0).
Micropython version was ESP32_GENERIC_C6-20250409-v1.25.0-preview.539.gdb8542707.
The same example works on ESP32-DevKitC-V4 for years.

import bluetooth

class BLE():
    def __init__(self, name):   
        self.name = name
        self.ble = bluetooth.BLE()
        self.ble.active(True)
        self.ble.irq(self.ble_irq)
        self.register()
        self.advertiser()

    def ble_irq(self, event, data):
        if event == 1:
            print('Connected')
        elif event == 2:
            self.advertiser()
            print('Disconnected')
        elif event == 3:
            buffer = self.ble.gatts_read(self.rx)
            message = buffer.decode('UTF-8').strip()
            print(message)            
           
    def register(self):        
        # Nordic UART Service (NUS)
        NUS_UUID = '6E400001-B5A3-F393-E0A9-E50E24DCCA9E'
        RX_UUID = '6E400002-B5A3-F393-E0A9-E50E24DCCA9E'
        TX_UUID = '6E400003-B5A3-F393-E0A9-E50E24DCCA9E'
            
        BLE_NUS = bluetooth.UUID(NUS_UUID)
        BLE_RX = (bluetooth.UUID(RX_UUID), bluetooth.FLAG_WRITE)
        BLE_TX = (bluetooth.UUID(TX_UUID), bluetooth.FLAG_READ | bluetooth.FLAG_NOTIFY)
            
        BLE_UART = (BLE_NUS, (BLE_TX, BLE_RX,))
        SERVICES = (BLE_UART, )
        ((self.tx, self.rx,), ) = self.ble.gatts_register_services(SERVICES)

    def send(self, data):
        self.ble.gatts_notify(0, self.tx, data + '\n')

    def advertiser(self):
        name = bytes(self.name, 'UTF-8')
        print('Advertising',name)
        self.ble.gap_advertise(100, bytes([0x02, 0x01, 0x02]) + bytes([len(name) + 1, 0x09]) + name)

ble = BLE("ESP32 uart")

while True:
    pass

[shariltumin]

Try changing your ble.gap_advertise() to:

         self.ble.gap_advertise(100, adv_data=b'\x02\x01\x06' + 
                                     bytes([len(name) + 1, 0x09]) + 
                                     name)

I tested it on ESP32-C3 and it works. It should also work on ESP32-C6.

[ondrejkarpis]

Thanks for Your advice but it still doesn't work.

[shariltumin]

I am sorry to hear that it is still not working for you.

I downloaded and flashed the latest firmware to my ESP32C6 board.

Here is the result of my test:

$ mpr mount .
Local directory . is mounted at /remote
Connected to MicroPython at /dev/ttyACM0
Use Ctrl-] or Ctrl-x to exit this shell
>
MicroPython v1.25.0 on 2025-04-15; ESP32C6 module with ESP32C6
Type "help()" for more information.
>>> 
>>> import qa_1
Advertising b'ESP32C6U'
Connected
hello
hello world
Advertising b'ESP32C6U'
Disconnected

I was using the "Serial Bluetooth Terminal" app on an old Android phone.

The difference between your code and the one I used:

$ diff qa.py qa_1.py
43c43,45
<         self.ble.gap_advertise(100, bytes([0x02, 0x01, 0x02]) + bytes([len(name) + 1, 0x09]) + name)
---
>         self.ble.gap_advertise(100, adv_data=b'\x02\x01\x06' + 
>                                     bytes([len(name) + 1, 0x09]) + 
>                                     name)
45c47
< ble = BLE("ESP32 uart")
---
> ble = BLE("ESP32C6U")

When I connected from the "BLE Scanner" app I see all NUS service and all its custom charateristics.

What client(central) app or program are you using?

[ondrejkarpis]

I updated the firmware to 1.25.0 and it works. I haven't noticed that a new version is out.
Thank You for help.