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Bluetooth Low Energy: Observer

Overview

The BLE Observer sample demonstrates Bluetooth Low Energy Observer role functionality. The application will periodically scan for devices nearby. If any found, prints the address of the device, the RSSI value, the Advertising type, and the Advertising data length to the console.

If the used Bluetooth Low Energy Controller supports Extended Scanning, you may enable CONFIG_BT_EXT_ADV in the project configuration file. Refer to the project configuration file for further details.

Requirements

Before you start, check that you have the required hardware and software:

Building the sample

Before you start building, remember to set up the environment first.

Use the following steps to build the BLE Observer sample on the command line.

  1. Open a terminal window.

  2. Go to my-workspace/ncs-playground directory created in the Setting up the environment section.

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    cd my-workspace/ncs-playground

  3. Build the sample using the west command, specifying the board (following the -b option) as connectkit_nrf52840:

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    west build -p always -b connectkit_nrf52840 samples/ble/observer

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    west build -p always -b connectkit_nrf52840 samples/ble/observer -- -DOVERLAY_CONFIG=overlay-extended.conf

    Tip

    The -p always option forces a pristine build, and is recommended for new users. Users may also use the -p auto option, which will use heuristics to determine if a pristine build is required, such as when building another sample.

  4. After running the west build command, the build files can be found in build/zephyr.

Flashing the firmware

The sample is designed to work with the UF2 Bootloader, so that you can easily flash the sample using the UF2 Bootloader. The firmware can be found in build/zephyr with the name zephyr.uf2.

To flash the firmware, complete the following steps:

  1. Push and hold the USER button and plug your board into the USB port of your computer. Release the USER button after your board is connected. The RGB LED turns green.

  2. It will mount as a Mass Storage Device called UF2BOOT.

  3. Drag and drop zephyr.uf2 onto the UF2BOOT volume. The RGB LED blinks red fast during flashing.

  4. Reset the board and the sample will start running.

Testing

After flashing the firmware to your board, complete the following steps to test it:

  1. Connect nRF52840 Connect Kit to your computer using the USB-C Cable.

  2. Open up a serial terminal, specifying the correct serial port that your computer uses to communicate with the board:

    Open up a terminal and run:

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    screen <serial-port-name> 115200
    1. Start PuTTY.

    2. Configure the correct serial port and click Open:

  3. Observe the output of the terminal. You should see the output, similar to what is shown in the following:

    Starting Observer Demo
Started scanning...
Device found: 49:38:F7:6C:CB:E0 (random) (RSSI -86), type 0, AD data len 31
Device found: 50:96:57:16:C0:DF (random) (RSSI -85), type 0, AD data len 29
Device found: CC:72:86:07:B4:7F (public) (RSSI -90), type 0, AD data len 19
Device found: CC:72:86:08:3F:F1 (public) (RSSI -83), type 0, AD data len 19
Device found: 5D:38:F1:C7:C5:BB (random) (RSSI -90), type 0, AD data len 31
...

    Starting Observer Demo
Started scanning...
Device found: CC:72:86:08:3F:F1 (public) (RSSI -82), type 0, AD data len 19
[DEVICE]: CC:72:86:08:3F:F1 (public), AD evt type 0, Tx Pwr: 127, RSSI -82 Data status: 0, AD data len: 19 Name:  C:1 S:1 D:0 SR:0 E:0 Pri PHY: LE 1M, Sec PHY: No packets, Interval: 0x0000 (0 ms), SID: 255
Device found: 76:B5:1F:C0:CF:0D (random) (RSSI -84), type 0, AD data len 26
[DEVICE]: 76:B5:1F:C0:CF:0D (random), AD evt type 0, Tx Pwr: 127, RSSI -84 Data status: 0, AD data len: 26 Name:  C:1 S:1 D:0 SR:0 E:0 Pri PHY: LE 1M, Sec PHY: No packets, Interval: 0x0000 (0 ms), SID: 255
Device found: CC:72:86:1D:4F:31 (public) (RSSI -71), type 0, AD data len 19
[DEVICE]: CC:72:86:1D:4F:31 (public), AD evt type 0, Tx Pwr: 127, RSSI -71 Data status: 0, AD data len: 19 Name:  C:1 S:1 D:0 SR:0 E:0 Pri PHY: LE 1M, Sec PHY: No packets, Interval: 0x0000 (0 ms), SID: 255
...