Regarding Python Scripts for nrf52840 to connect and transfer data.

[Zero.cool]

Hi ,

What I am trying:- 

-connect the custom board with nrf52840 chip using nrf52 dongle on pc with python.

-Already set some commands on custom board so when my pc (via dongle) connects to custom board, I want to send some commands and accordingly receive the response.

For this I got my hands-on nrf dongle to give my laptop a BLE access.

And I am trying to access the board using dongle (using python script) and I am getting below error,

raise NordicSemiException('Failed to {}. Error code: {}'.format(wrapped.__name__, err_code))
pc_ble_driver_py.exceptions.NordicSemiException: Failed to open. Error code: 13.

Would anyone able to tell me how do i resolve this. 

I want to have python code that can connect and do some data transfer over BLE using Dongle connected to my pc and I have tried with hart_rate_monitor unsuccessfully. 

EDIT 1:- I am able to scan and connect my board using the nRF Connect windows app. Same I wanted to implement over python.

Thanks,

Hinesh

[tesc]

Hi,

The line

BASE_UUID = BLEUUIDBase([0x8E, 0xC9, 0x00, 0x00, 0xF3, 0x15, 0x4F, 0x60,
                         0x9F, 0xB8, 0x83, 0x88, 0x30, 0xDA, 0xEA, 0x50])

creates a base UUID of

0x8EC9xxxx-F315-4F60-9FB8-838830DAEA50

As you can see, each value in the array of hexadecimal values corresponds to one byte of the base UUID. The two bytes that are written using x in the UUID are filled in using the call to BLEUUID, so that e.g.

    BLE_DFU_BUTTONLESS_CHAR_UUID        = BLEUUID(0x0003, BASE_UUID)

creates the UUID of

0x8EC90003-F315-4F60-9FB8-838830DAEA50

So you must divide your UUID into base UUID and 16 bit part, exactly the same way.

Regards,
Terje

[Zero.cool]

I have tried your suggestions and changed

CCCD_UUID = '00002902-0000-1000-8000-00805f9b34fb'

DC_SERVICE_UUID = '00001111-0000-1000-8000-00805f9b34fb'
DATA_CHAR_UUID  = '00002222-0000-1000-8000-00805f9b34fb'
DATA2_CHAR_UUID = '00003333-0000-1000-8000-00805f9b34fb'


DC_SERVICE_BASE_UUID = BLEUUIDBase([0x00, 0x00, 0x22, 0x22, 0x00, 0x00, 0x10, 0x00,
                                    0x80, 0x00, 0x00, 0x80, 0x5f, 0x9b, 0x34, 0xfb])
## Also Tried with above CCCD_UUID for checking as below , but not worked
#--CCCD_BASE_UUID = BLEUUIDBase([0x00, 0x00, 0x29, 0x02, 0x00, 0x00, 0x10, 0x00,
#                              0x80, 0x00, 0x00, 0x80, 0x5F, 0x9B, 0x34, 0xFB])
# Buttonless characteristics
BLE_DFU_BUTTONLESS_CHAR_UUID = BLEUUID(0x2902, DC_SERVICE_BASE_UUID)
BLE_DFU_BUTTONLESS_BONDED_CHAR_UUID = BLEUUID(0x2901, DC_SERVICE_BASE_UUID)
## The 0x2902 and 0x2901 are I have checked via nrf connect app and they are showing
## same. I have also changed as per the suggestionns of 0x2222 and 0x1111. But
## not able to connect

self.adapter.service_discovery(new_conn)
        self.adapter.enable_notification(new_conn,
                                         BLEUUID(0x2901, DC_SERVICE_BASE_UUID))
## Here also changes and tested.

Still I get this error as below.

ATT MTU exchanged: conn_handle=0 att_mtu=23
ATT MTU exchange response: conn_handle=0
Traceback (most recent call last):
  File "C:/My_Projects/Script.py", line 267, in <module>
    main(serial_port)
  File "C:/My_Projects/Script.py", line 248, in main
    conn_handle = collector.connect_and_discover()
  File "C:/My_Projects/Script.py", line 198, in connect_and_discover
    BLEUUID(0x2901, DC_SERVICE_BASE_UUID))  # BLEUUID(BLEUUID.Standard.battery_level))
  File "C:\Python27\lib\site-packages\pc_ble_driver_py\ble_driver.py", line 125, in wrapper
    err_code = wrapped(*args, **kwargs)
  File "C:\Python27\lib\site-packages\pc_ble_driver_py\ble_adapter.py", line 254, in enable_notification
    raise NordicSemiException('CCCD not found')
pc_ble_driver_py.exceptions.NordicSemiException: CCCD not found

I see one function below

    def enable_notification(self, conn_handle, uuid):
        cccd_list = [1, 0]

        handle = self.db_conns[conn_handle].get_cccd_handle(uuid)
        if handle == None:
            raise NordicSemiException('CCCD not found')

So in this function I believe the passed 'UUID' is not correct.

But passed in the function is correct.

can you input here what Is going wrong?

(Kindly ignore other copy & paste as it was not showing prior log of and log in)

Thanks,

[tesc]

Hi,

Why are you still defining BLE_DFU_BUTTONLESS_CHAR_UUID and BLE_DFU_BUTTONLESS_BONDED_CHAR_UUID? That was an example, for how to make UUIDs. You should do e.g.:

DC_SERVICE_BASE_UUID = BLEUUIDBase([0x00, 0x00, 0x22, 0x22, 0x00, 0x00, 0x10, 0x00,
                                    0x80, 0x00, 0x00, 0x80, 0x5f, 0x9b, 0x34, 0xfb])

DATA_CHAR_UUID  = BLEUUID(0x2222, DC_SERVICE_BASE_UUID)
DATA2_CHAR_UUID = BLEUUID(0x3333, DC_SERVICE_BASE_UUID)

self.adapter.service_discovery(new_conn)
self.adapter.enable_notification(new_conn, DATA_CHAR_UUID)

If you attach a screenshot of what you get in nRF Connect then I can try to explain what it means. It sounds like you have mixed up several UUIDs (what they mean and how they are used.)

Regards,
Terje

[Zero.cool]

Hi tesc

Below is my output of the terminal.

File "C:\Python27\lib\site-packages\pc_ble_driver_py\ble_adapter.py", line 254, in enable_notification
    raise NordicSemiException('CCCD not found')
pc_ble_driver_py.exceptions.NordicSemiException: CCCD not found

Also The BLE_DFU_BUTTONLESS_CHAR_UUID is there, but not using them,

[tesc]

Hi,

Can you provide a screenshot or image from nRF Connect, showing the UUIDs that are found on the device?

Regards,
Terje