Automate nRF52840 Dongle running pc-nrfconnect-ble

[FernandoM]

Hello,

 I'm very unexperienced with low-level programming, so I apologize is some of my questions make little sense.

  We have this board that sends telemetry data using a nRF52840 to a Window 10 PC.  Looking for a quick and dirty way to scan for the board, connect to it, and record the RSSI value I found out the nRF52840 dongle.  Running Bluetooth Low Energy app that comes with nRF Connect for Desktop works like a charm, but now I'm looking for a way to replicate this thru LabView. I took a gander at the serial port communications between the app and the dongle and it's mostly HEX commands, so I tried looking around github for a piece of code or example that I could use to duplicate these commands, but I can't figure out where or what to look for..

 I'm hoping someone can point me to a piece of code/example or document that explains how to send and read the commands to a nRF52840 dongle programmed with pc-nrfconnect-ble.

Thanks.

[Vidar Berg]

Hello,

Attached below is a python script for the pc-ble-driver-py I quickly put together which will connect to any BLE device named 'TARGET_DEV_NAME' and start logging the RSSI. You can use it with the same dongle and FW you use with the Bluetooth low energy app.

Fullscreen 1362.rssi_logger.py Download

#
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import sys
import time
import logging
from queue import Queue, Empty
from pc_ble_driver_py.observers import *

TARGET_DEV_NAME = "Nordic_UART"
CONNECTIONS = 1
CFG_TAG = 1

global config, BLEDriver, BLEAdvData, BLEEvtID, BLEAdapter, BLEEnableParams, BLEGapTimeoutSrc, BLEUUID, BLEUUIDBase, BLEConfigCommon, BLEConfig, BLEConfigConnGatt, BLEGapScanParams, BLEConfigConnGap, BLEGapConnParams
from pc_ble_driver_py import config
config.__conn_ic_id__ = "NRF52"
# noinspection PyUnresolvedReferences
from pc_ble_driver_py.ble_driver import (
        BLEDriver,
    BLEAdvData,
    BLEEvtID,
    BLEEnableParams,
    BLEGapTimeoutSrc,
    BLEUUID,
    BLEUUIDBase,
    BLEGapScanParams,
    BLEGapConnParams,
    BLEConfigCommon,
    BLEConfig,
    BLEConfigConnGatt,
    BLEConfigConnGap,
)


def init(conn_ic_id):
    # noinspection PyGlobalUndefined
    global config, BLEDriver, BLEAdvData, BLEEvtID, BLEAdapter, BLEEnableParams, BLEGapTimeoutSrc, BLEUUID, BLEUUIDBase, BLEConfigCommon, BLEConfig, BLEConfigConnGatt, BLEGapScanParams, BLEConfigConnGap, BLEGapConnParams
    from pc_ble_driver_py import config

    config.__conn_ic_id__ = conn_ic_id
    # noinspection PyUnresolvedReferences
    from pc_ble_driver_py.ble_driver import (
        BLEDriver,
        BLEAdvData,
        BLEEvtID,
        BLEEnableParams,
        BLEGapTimeoutSrc,
        BLEUUID,
        BLEUUIDBase,
        BLEGapScanParams,
        BLEGapConnParams,
        BLEConfigCommon,
        BLEConfig,
        BLEConfigConnGatt,
        BLEConfigConnGap,
    )

    # noinspection PyUnresolvedReferences
    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 NusCollector(BLEDriverObserver, BLEAdapterObserver):
    
    CUS_BASE_UUID = BLEUUIDBase([
            0x6e, 0x40, 0x00, 0x00, 0xb5, 0xa3, 0xf3, 0x93, 0xe0, 0xa9, 0xe5, 0x0e, 0x24, 0xdc, 0xca, 0x9e
        ])
    CUS_WR_UUID = BLEUUID(0x0002, CUS_BASE_UUID)
    CUS_RD_UUID = BLEUUID(0x0003, CUS_BASE_UUID)
    def __init__(self, adapter):
        super(NusCollector, self).__init__()
        self.first = 1
        self.adapter = adapter
        self.conn_q = Queue()
        self.adapter.observer_register(self)
        self.adapter.driver.observer_register(self)
        self.adapter.default_mtu = 247
        self.nus_base = BLEUUIDBase([
            0x6e, 0x40, 0x00, 0x00, 0xb5, 0xa3, 0xf3, 0x93, 0xe0, 0xa9, 0xe5, 0x0e, 0x24, 0xdc, 0xca, 0x9e
        ], 0x2)
        self.nus_rx = BLEUUID(0x0002, self.nus_base)
        self.nus_tx = BLEUUID(0x0003, self.nus_base)

    def open(self):
        self.adapter.driver.open()
        if config.__conn_ic_id__ == "NRF51":
            self.adapter.driver.ble_enable(
                BLEEnableParams(
                    vs_uuid_count=1,
                    service_changed=0,
                    periph_conn_count=0,
                    central_conn_count=1,
                    central_sec_count=0,
                )
            )
        elif config.__conn_ic_id__ == "NRF52":
            gatt_cfg = BLEConfigConnGatt()
            gatt_cfg.att_mtu = self.adapter.default_mtu
            gatt_cfg.tag = CFG_TAG
            self.adapter.driver.ble_cfg_set(BLEConfig.conn_gatt, gatt_cfg)

            conn_cfg = BLEConfigConnGap()
            conn_cfg.conn_count = 1
            conn_cfg.event_length = 320
            self.adapter.driver.ble_cfg_set(BLEConfig.conn_gap, conn_cfg)

            self.adapter.driver.ble_enable()
            self.adapter.driver.ble_vs_uuid_add(NusCollector.CUS_BASE_UUID)



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

    def connect_and_discover(self):
        scan_duration = 5
        scan_params = BLEGapScanParams(interval_ms=200, window_ms=150, timeout_s=scan_duration)

        self.adapter.driver.ble_gap_scan_start(scan_params=scan_params)

        try:
            new_conn = self.conn_q.get(timeout=scan_duration)
            self.adapter.service_discovery(new_conn)
            self.adapter.driver.ble_gap_rssi_start(new_conn, 0, 0)
            return new_conn
        except Empty:
            print("No device advertising with name {TARGET_DEV_NAME} found.")
            return None

    def on_gattc_evt_exchange_mtu_rsp(self, ble_driver, conn_handle, status, att_mtu):
        print("ATT MTU updated to {}".format(att_mtu))
    
    def on_gap_evt_data_length_update(
        self, ble_driver, conn_handle, data_length_params
    ):
        print("Max rx octets: {}".format(data_length_params.max_rx_octets))
        print("Max tx octets: {}".format(data_length_params.max_tx_octets))
        print("Max rx time: {}".format(data_length_params.max_rx_time_us))
        print("Max tx time: {}".format(data_length_params.max_tx_time_us))

    def on_gatts_evt_exchange_mtu_request(self, ble_driver, conn_handle, client_mtu):
        print("Client requesting to update ATT MTU to {} bytes".format(client_mtu))
    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_adv_report(
        self, ble_driver, conn_handle, peer_addr, rssi, adv_type, adv_data
    ):
        conn_params = BLEGapConnParams(min_conn_interval_ms=7.5, max_conn_interval_ms=7.5, conn_sup_timeout_ms=4000, slave_latency=0)
        
        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, conn_params = conn_params, tag=CFG_TAG)

    def on_notification(self, ble_adapter, conn_handle, uuid, data):
        if len(data) > 32:
            data = "({}...)".format(data[0:10])
        print("Connection: {}, {} = {}".format(conn_handle, uuid, data))

    def on_gap_evt_rssi_changed(self, ble_driver, conn_handle, rssi):
        print("RSSI: {}".format(rssi))


def main(selected_serial_port):
    print("Serial port used: {}".format(selected_serial_port))
    driver = BLEDriver(
        serial_port=selected_serial_port, auto_flash=False, baud_rate=1000000, log_severity_level="info"
    )

    adapter = BLEAdapter(driver)
    collector = NusCollector(adapter)
    collector.open()
    conn = collector.connect_and_discover()

    while conn is not None:
        time.sleep(10)
    collector.adapter.disconnect(conn)
    collector.close()


def item_choose(item_list):
    for i, it in enumerate(item_list):
        print("\t{} : {}".format(i, it))
    print(" ")

    while True:
        try:
            choice = int(input("Enter your choice: "))
            if (choice >= 0) and (choice < len(item_list)):
                break
        except Exception:
            pass
        print("\tTry again...")
    return choice


if __name__ == "__main__":
    logging.basicConfig(
        level="INFO",
       format="%(asctime)s [%(thread)d/%(threadName)s] %(message)s",
    )
    serial_port = None
    if len(sys.argv) < 2:
        print("Please specify connectivity IC identifier (NRF51, NRF52)")
        exit(1)
    init(sys.argv[1])
    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 = item_choose(choices)
        serial_port = descs[choice].port
    main(serial_port)
    quit()

Steps for testing the script:

1. Install pc-ble-driver-py through PyPi: $ pip install --user pc-ble-driver-py

2. Change TARGET_DEV_NAME in the script to match your device.

3. Run script with python: $ python3 rssi_logger.py NRF52 <COM port for nrf52840 dongle>

After the connection has been established you should start seeing the measured RSSIs from the connection:

$ python3 rssi_logger.py NRF52 /dev/ttyACM0
Serial port used: /dev/ttyACM0
2022-04-11 15:54:27,049 [139762313049856/LogThread] Successfully opened /dev/ttyACM0. Baud rate: 1000000. Flow control: none. Parity: none.
Received advertisment report, address: 0xC4A1E304973B, device_name: Nordic_UART
New connection: 0
Client requesting to update ATT MTU to 247 bytes
Max rx octets: 251
Max tx octets: 251
Max rx time: 2120
Max tx time: 2120
RSSI: -39
RSSI: -37
RSSI: -37
RSSI: -37
RSSI: -40
RSSI: -42
RSSI: -38
RSSI: -39
RSSI: -39
RSSI: -39

I do not have much experience with LabView, but I hope you will be able to parse the log output from it.

Best regards,

Vidar

[FernandoM]

Thank you very much Vidar, unfortunately I wasn't able to take the time to learn Python (my programming experience is currently limited to Labview and VB 6.0 ;-). 

At the end I took a different approach.  First I was able to open "pc-ble-driver" in VS2022 and build the "heart_rate_collector".  Then I modified the code to allow extended advertisements and to ouput the rssi.  Once I got the EXE where I wanted, I simply run it using System Exec.vi in Labview.

Not the most elegant solution, but it's the quick and dirty way for someone looking for a very basic interface between the nRF52840 dongle and Labview.

Quick side note, I also tried to write a .NET C# application using Windows UWP BluetoothLEAdvertisementWatcher and some cheapo USB Bluetooth adapters from Amazon, but even after enabling the AllowExtendedAdvertisements property, I wasn't able to scan extended advertisements, only the BLE legacy ones.

[Vidar Berg]

Good to hear that you found a solution, thanks for the update.

FernandoM said:

Quick side note, I also tried to write a .NET C# application using Windows UWP BluetoothLEAdvertisementWatcher and some cheapo USB Bluetooth adapters from Amazon, but even after enabling the AllowExtendedAdvertisements property, I wasn't able to scan extended advertisements, only the BLE legacy ones.

Extended advertisements must also be supported by the Bluetooth adapter. Maybe that is why it did not work.