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,

Can you provide the full command that you run (for starting the python script) and all output to the command line afterwards? (Both what parameters you send to the script, any debug output, and the full traceback may give clues as to what is the problem.)

Regards,
Terje

[Zero.cool]

HI tesc

Actually I have resolved the above error.

By going through various questions and answers here I came to know some tools.

So When I was opening 'nrf connect' windows app , it was flashing firmware and I was having impression that this will be samefirmware will be used for scanning and connect via python. But It was not working.

And the I have installed windows command line tools and format the board using 'nrfproject' command. And Let the python  application 'Hear rate monitor' do the flashing. Then it started working.

It seems the mismatch on the firmware version on nrf52840 PDK Board (that I am using as dongle to connect to custom board via my pc).

So To come on another query I have,

Can you point me any example or script that can do the same work as 'nrf connect' does?

Scan, connect (to particular given mac id) and explore services of connected device.

Basically I am trying what I have explained on above question.

This would be very help full for us as we are already on advance stage for development.

Thanks,

Hinesh

[tesc]

Hi,

You will see in the heart rate collector example of pc-ble-driver-py, that there is a condition on the device name (variable "dev_name") in the on_gap_evt_adv_report() funciton. So in that example, connections are filtered based on device name. You can replace that if block with any other check, including a check on the "peer_addr" which is the address of the advertising device. In the same example, service discovery is done in connect_and_discover().

Regards,
Terje

[Zero.cool]

So Basically in my understanding, Please check comments on below code.

And peer address here is the mac id of the advertising device or the name ?

    def on_gap_evt_adv_report(self, ble_driver, conn_handle, peer_addr, rssi, adv_type, adv_data): #peer address is my adverstiseing device that needs to be connected
        dev_name_list = None #Here change with dongle name 
        if BLEAdvData.Types.complete_local_name in adv_data.records:
            dev_name_list = adv_data.records[BLEAdvData.Types.complete_local_name]

        elif BLEAdvData.Types.short_local_name in adv_data.records:
            dev_name_list = adv_data.records[BLEAdvData.Types.short_local_name]

I will do a trial now and let you know about result.

EDIT:- I have edited the parameters but upon running, It's asking for 
'Please specify connectivity IC identifier (NRF51, NRF52)'

I have also hard coded the device in config.py file on __conn_ic_id__ = "NRF52".

But still while running the code it's asking for the IC identifier.

Here I am trying to connect to device (example) with mac :- 11:22:33:44:55:66.
This device I am able to see in the scan list as address and I can see the device name as well.

Any comments on this?

Thanks,

Hinesh

[tesc]

Hi,

You will need something along the lines of:

if (peer_addr == TARGET_PEER_ADDR)
    self.adapter.connect(peer_addr)

Instead of the current if that checks the dev_name. And also, you must define the TARGET_PEER_ADDR constant to be the address of the device, similar to how in the example they define a constant TARGET_DEV_NAME for the name of the device.

For the error that you see, you will see at at the very end of the heart_rate_collector.py the code that leads to that error being displayed. It is code handling the arguments that you provide when running the example. If you want to use a hard coded connection IC ID then you can change that test, and also change the line "init(sys.argv[1])" to use the hard coded connection IC ID instead of sys.argv[1] as its argument.

Please note that the argv array contains all the arguments that you provide on the command line, and so if you do not use the first argument any more then you must do additional changes in order for the other arguments to work as intended. I will leave it up to you to decide what arguments you want and for what purposes.

I cannot do the work for you, but hopefully this should be enough for you to get going.

Regards,
Terje

[Zero.cool]

Hi tesc

From your suggestions I am able to connect to specific device via dongle/dk connected to any com port on my pc.

Thank you very much for this.

While going through the forums and also over internet I found for read and write operation gatt libraries are used in python.

Well, I am using windows and I was not able to find the same for windows in python for read and write from my nordic board via my pc using python.

I can find below function in ble_driver.py. but 

def ble_gattc_write(self, conn_handle, write_params)
def ble_gattc_read(self, conn_handle, handle, offset)
(using the BLEDriver class I tried, but not success ,May be I am doing something wrong here or lacking knowledge.)

It will be good if you can input here, 

Thanks, 

[tesc]

Hi,

There is a close mapping between those python functions and the SoftDevice API. More specifically, the functions that you refer to correspond to sd_ble_gattc_write() and sd_ble_gattc_read().

Please note that the current version of pc-ble-driver-py uses the s132 SoftDevice version 3.1.0. We are currently working on a new version of pc-ble-driver using s132 and s140 versions 6.1.0, and pc-ble-driver-py is likely to be updated further down the road.

Unfortunately we do not seem to have any other examples than the ones in the python/pc-ble-driver-py/examples folder.

Regards,
Terje

[Zero.cool]

Hi tesc

Thank you very much for the input.

From example Hart rate collector, I have made some changes require to connect to my device (having soft device 140).

I am able to scan and I also thought I am able to connect (by hard coding the device mac and name on the serial port) as well.

But I am getting below error.,

"Received advertisment report, address: 0xAABBCCDDEEFF, device_name: MYDEVICE
New connection: 0
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 256, in <module>
    main(serial_port)
  File "C:/My_Projects/Script.py", line 237, in main
    conn_handle = collector.connect_and_discover()
  File "C:/My_Projects/Script.py", line 187, in connect_and_discover
    self.adapter.enable_notification(new_conn, 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

Process finished with exit code 1
"

I checked in

self.adapter.enable_notification(new_conn, BLEUUID(BLEUUID.Standard.battery_level))

Where I have tried to input my UUID as below,

self.adapter.enable_notification(new_conn,MY_UUID, BLEUUID(BLEUUID.Standard.battery_level))

From the file ble_driver.py

def enable_notification(self, conn_handle, uuid):

where 
I am passing collection handle but 

handle = self.db_conns[conn_handle].get_cccd_handle(uuid)

still I get NONE on conn_handle. so is it my device that is not sending or I am not sharing proper UUID?
The UUID IS checked by me for correctness, But If that's not correct I can correct by trying.

It will be really helpful to have your input So that I can do read and write to my device via nordic dongle.

By the way:- I am working with nordic dongle to remove other hw requirement possibility.
we have checked the communication working but by different hw to verify the ID's on customized device.
and we successfully checked and received data.

Here your input will be very very helpful to complete read and write.
Also to check if that's the right way.


Thanks,
Hinesh