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,

Yes, that error would be expected if you try enable_notification() with a characteristic UUID that has not been found on the device. For instance, the line...

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

...will try to enable notifications on the Bluetooth SIG specified Battery Level characteristic (i.e. UUID 0x2A19). If you use a custom UUID then you do not have a BLEUUID() but a full 128 bit UUID. Now, if your MY_UUID is correctly formatted then you should be able to use

self.adapter.enable_notification(new_conn, MY_UUID)

You can connect to the device from nRF Connect in order to investigate what characteristics (and UUIDs) are present on the device.

Regards,
Terje

[Zero.cool]

Hi tesc,

This are good suggestions and I have tried them as well without success.

in self.adapter.enable_notification(new_conn,MY_UUID) I kept and also double checked in nRF connect app but still not able to send data.

When I run the script

I am able to scan and connect to my device.(provide your input for below debug output)

Connected to pydev debugger (build 181.4892.64)
Serial port used: COM10
Enabling larger ATT MTUs
Received advertisment report, address: 0x5031ADC0000A, device_name: MY_DEVICE
New connection: 0
ATT MTU exchanged: conn_handle=0 att_mtu=23
ATT MTU exchange response: conn_handle=0

The UUID I am passing I have also checked in python debug and it's same.

And on Below line From file ble_adapter.py in

def enable_notification(self, conn_handle, uuid):
I went to for more debug.

and I found is 
assert isinstance(uuid, BLEUUID), 'Invalid argument type'
AssertionError: Invalid argument type

I am not able to understand what is BLEUUID here. I changed BLEUUID in
self.adapter.enable_notification to MY_UUID. and Still no connection.

could you help in here. Also If you can tell about read and write function which
I intent to use so that I will complete my script. and once tested
I can share here so other can also be benefited.


Thanks,

[tesc]

Hi,

BLEUUID is a class, and you use BLEUUID() to create an instance of that class. I.e., you use the BLEUUID() function to generate a BLEUUID object.

BLEUUID takes one or two arguments. The first argument is the 16 bit UUID. The second argument is optional, and is the base UUID, of type BLEUUIDBase. If the second argument is not provided then a 16 bit UUID is generated (using the special Bluetooth SIG assigned base UUID to be used with 16 bit UUIDs.)

I did find an example using both standard (16 bit) UUIDs and user generated (128 bit) UUIDs, as part of pc-nrfutil:

    BASE_UUID = BLEUUIDBase([0x8E, 0xC9, 0x00, 0x00, 0xF3, 0x15, 0x4F, 0x60,
                             0x9F, 0xB8, 0x83, 0x88, 0x30, 0xDA, 0xEA, 0x50])
                             
    # Buttonless characteristics
    BLE_DFU_BUTTONLESS_CHAR_UUID        = BLEUUID(0x0003, BASE_UUID)
    BLE_DFU_BUTTONLESS_BONDED_CHAR_UUID = BLEUUID(0x0004, BASE_UUID)
    SERVICE_CHANGED_UUID                = BLEUUID(0x2A05)

Notice how in order to create a custom UUID, you first use BLEUUIDBase() to generate the BLEUUIDBase, and then provide that BLEUUIDBase object as the second argument to BLEUUID().

Regards,
Terje

[Zero.cool]

Hi tesc

MY_UUID = '00001111-0000-1000-8000-00805f9b34fb'

My UUID is as above, And I have used as per your prev. comment. I checked with nrf connect mobile app.
Still I was getting error.

Below is my console output after I used

BLE_DFU_BUTTONLESS_CHAR_UUID = BLEUUID(0x0003, BASE_UUID)

in

self.adapter.enable_notification(new_conn, BLEUUID(0x0003, MY_UUID)

Serial port used: COM10
Enabling larger ATT MTUs
Received advertisment report, address: 0x5031ADC0000A, device_name: POC1_2-3
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:\Program Files\JetBrains\PyCharm Community Edition 2018.1.3\helpers\pydev\pydevd.py", line 1664, in <module>
    main()
  File "C:\Program Files\JetBrains\PyCharm Community Edition 2018.1.3\helpers\pydev\pydevd.py", line 1658, in main
    globals = debugger.run(setup['file'], None, None, is_module)
  File "C:\Program Files\JetBrains\PyCharm Community Edition 2018.1.3\helpers\pydev\pydevd.py", line 1068, in run
    pydev_imports.execfile(file, globals, locals)  # execute the script
  File "C:/My_Projects/Script.py", line 263, in <module>
    main(serial_port)
  File "C:/My_Projects/Script.py", line 244, in main
    conn_handle = collector.connect_and_discover()
  File "C:/My_Projects/Script.py", line 194, in connect_and_discover
    self.adapter.enable_notification(new_conn, BLEUUID(0x0003, DC_SERVICE_UUID))#BLEUUID(BLEUUID.Standard.battery_level))
  File "C:\Python27\lib\site-packages\pc_ble_driver_py\ble_driver.py", line 882, in __init__
    assert isinstance(base, BLEUUIDBase), 'Invalid argument type'
AssertionError: Invalid argument type

Still the error.

I am attaching my script so that you can check and provide input.

This is for your information on how I am trying to implement.

Fullscreen Range_Test - Copy.py Download

import Queue

import json
import time
import sys

from datetime import datetime, timedelta
from bitstruct import *
from pprint import pformat
import binascii
from pc_ble_driver_py.observers import *
from nordicsemi.ble_adapter import *

try:
    with open("Config_Files/Connection_Settings.json")as conn:
        config = json.load(conn)
except Exception as e:
    print str(e)
    print 'Could not open settings file'
    raw_input("Press ENTER to exit...")
    quit()


DEV_MAC = config['dev_mac']


REPEAT_COUNT = 25

RAW_TYPE = TEMP  # Temp sensor
RAW_COUNT = 10  # Sample count
RAW_RATE = 0  # Sampling freq

TARGET_DEV_NAME ="50:31:AD:C0:00:0A"
port_enter = "COM10"
device = "NRF52"
CONNECTIONS = 1
serial_port = "COM10"
dev_name = "50:31:AD:C0:00:0A"
# Creating command packet
temp = pack('u8u16f32', RAW_TYPE, RAW_COUNT, RAW_RATE)
pkt = byteswap('124', temp)

HEADER_SIZE = 3

_EOT_T = 'u1'
_TYPE_T = 'u3'
_TID_T = 'u4'
_SEQ_NUM_T = 'u16'

__BYTEALIGN = '12'

__DATA_FORMAT = _TID_T + _TYPE_T + _EOT_T + _SEQ_NUM_T

sensorType = RAW_TYPE
sampleCount = RAW_COUNT
samplingFreq = RAW_RATE
##
#Data saving part 
##

##### NRF PART ################

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

DC_SERVICE_UUID = '00001111-0000-1000-8000-00805f9b34fb'

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

# Buttonless characteristics
BLE_DFU_BUTTONLESS_CHAR_UUID = BLEUUID(0x0003, BASE_UUID)
BLE_DFU_BUTTONLESS_BONDED_CHAR_UUID = BLEUUID(0x0004, BASE_UUID)
SERVICE_CHANGED_UUID = BLEUUID(0x2A05)
def init(conn_ic_id):
    global BLEDriver, BLEAdvData, BLEEvtID, BLEAdapter, BLEEnableParams, BLEGapTimeoutSrc, BLEUUID
    from pc_ble_driver_py import config
    config.__conn_ic_id__ = conn_ic_id
    from pc_ble_driver_py.ble_driver import BLEDriver, BLEAdvData, BLEEvtID, BLEEnableParams, BLEGapTimeoutSrc, BLEUUID
    from pc_ble_driver_py.ble_adapter import BLEAdapter
    global nrf_sd_ble_api_ver
    nrf_sd_ble_api_ver = config.sd_api_ver_get()


class HRCollector(BLEDriverObserver, BLEAdapterObserver):
    def __init__(self, adapter):
        super(HRCollector, self).__init__()
        self.adapter = adapter
        self.conn_q = Queue.Queue()
        self.adapter.observer_register(self)
        self.adapter.driver.observer_register(self)

    def open(self):
        self.adapter.driver.open()

        ble_enable_params = BLEEnableParams(vs_uuid_count=1,
                                            service_changed=False,
                                            periph_conn_count=0,
                                            central_conn_count=CONNECTIONS,
                                            central_sec_count=CONNECTIONS)
        if nrf_sd_ble_api_ver >= 3:
            print("Enabling larger ATT MTUs")
            ble_enable_params.att_mtu = 50

        self.adapter.driver.ble_enable(ble_enable_params)

    def close(self):
        self.adapter.driver.close()

    @property
    def connect_and_discover(self):
        self.adapter.driver.ble_gap_scan_start()
        new_conn = self.conn_q.get(timeout=60)

        if nrf_sd_ble_api_ver >= 3:
            att_mtu = self.adapter.att_mtu_exchange(new_conn)

        self.adapter.service_discovery(new_conn)
        self.adapter.enable_notification(new_conn, BLEUUID(0x0003, DC_SERVICE_UUID))#BLEUUID(BLEUUID.Standard.battery_level))
        # self.adapter.enable_notification(new_conn, BLEUUID(BLEUUID.Standard.heart_rate))
        return new_conn

    def on_gap_evt_connected(self, ble_driver, conn_handle, peer_addr, role, conn_params):
        print('New connection: {}'.format(conn_handle))
        self.conn_q.put(conn_handle)

    def on_gap_evt_disconnected(self, ble_driver, conn_handle, reason):
        print('Disconnected: {} {}'.format(conn_handle, reason))

    def on_gap_evt_timeout(self, ble_driver, conn_handle, src):
        if src == BLEGapTimeoutSrc.scan:
            ble_driver.ble_gap_scan_start()

    def on_gap_evt_adv_report(self, ble_driver, conn_handle, peer_addr, rssi, adv_type, adv_data):
        dev_name_list = None
        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]

        else:
            return

        dev_name = "".join(chr(e) for e in dev_name_list)
        address_string = "".join("{0:02X}".format(b) for b in peer_addr.addr)
        print('Received advertisment report, address: 0x{}, device_name: {}'.format(address_string,
                                                                                    dev_name))

        if (dev_name == TARGET_DEV_NAME):
            self.adapter.connect(peer_addr)

    def on_notification(self, ble_adapter, conn_handle, uuid, data):
        print('Connection: {}, {} = {}'.format(conn_handle, uuid, data))

    def on_att_mtu_exchanged(self, ble_driver, conn_handle, att_mtu):
        print('ATT MTU exchanged: conn_handle={} att_mtu={}'.format(conn_handle, att_mtu))

    def on_gattc_evt_exchange_mtu_rsp(self, ble_driver, conn_handle, **kwargs):
        print('ATT MTU exchange response: conn_handle={}'.format(conn_handle))


def main(serial_port):
    print('Serial port used: {}'.format(serial_port))
    driver = BLEDriver(serial_port=serial_port, auto_flash=True)
    adapter = BLEAdapter(driver)
    collector = HRCollector(adapter)
    collector.open()
    conn_handle = collector.connect_and_discover()
    # adapter.write_req(conn_handle, CCCD_UUID, [3])#RAW_TYPE)
    # collector.connect_and_discover()
   


if __name__ == "__main__":
    serial_port = None
    # if len(sys.argv) < 2:
    #     print("Please specify connectivity IC identifier (NRF51, NRF52)")
    #     exit(1)
    init("NRF52")
    if len(sys.argv) == 3:
        serial_port = sys.argv[2]
    else:
        descs = BLEDriver.enum_serial_ports()
        choices = ['{}: {}'.format(d.port, d.serial_number) for d in descs]
        choice = '0'  # item_choose(choices)
        serial_port = port_enter  # "COM12" #descs[choice].port
        main(serial_port)
        quit()

##### NRF PART ###### #########

Thnaks,

[tesc]

Hi,

You need to make the DC_SERVICE_UUID in the same way as the BLE_DFU_BUTTONLESS_CHAR_UUID was made in the example code. (You should not just copy and paste the code, as you are using different UUIDs than what was used in the example code.)

More specifically, on the line "self.adapter.enable_notification(new_conn, BLEUUID(0x0003, DC_SERVICE_UUID))" you provide DC_SERVICE_UUID, which should be a BLEUUIDBase object and not a string.

Regards,
Terje

[tesc]

Hi,

Also, on the line I mentioned, you use the value 0x0003, but that should be byte 12 and 13 of the full UUID, and what you call DC_SERVICE_UUID should really be called DC_SERVICE_BASE_UUID. Those two parts together are used by BLEUUID to generate the full UUID.

Regards,
Terje

[Zero.cool]

Hi tesc

You have explained well.

But two questions:-

1. How do I convert UUID to BLEUUDIBase Format? just separating  with '0x00' will not work (I think).

2. This is for writing, once this command given , device will start transmitting data. So I have to initiate a reader thread/function as well. is there any read function as I was not able to find in examples.

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