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In this application note the ml_ble_platform/sensor_base demo is used as an example. This application provides a platform for supporting external sensors and logging raw sample values over BLE. IMU readings are sent as notifications on ACC_SAMPLES (UUID=110d8470-2eb3-11eb-bf0c-8ff42f5dc2bc and value handle=0x1d) characteristic value change. Refer to “ML_BLE_Platform BLE Interface Specification” for more information.

1. Uploading a BLE Demo to the Target

BLE demos included in the NAVQ Plus Linix BSP consist of two parts: the bootloader and a working (“mission“) firmware.

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  1. Sync the Telink programmer with the target:

    Code Block
    sudo tcdb 9518 sws

  2. Program the bootloader with the 0 offset:

    Code Block
    sudo tcdb 9518 wf 0 -i ./bootloader.bin -b

  3. Program the demo binary with the 1000 offset:

    Code Block
    sudo tcdb 9518 wf 1000 -i ./sensor_base_mission-evb-002.001.000.bin -b

  4. Reset the target.

2. Checking a Local Interface

  1. Verify that a local interface is detected with hcitool:

    Code Block
    user@imx8mpnavq:~$ sudo hcitool dev
Devices:
	hci0	D4:53:83:C4:E5:5B

    Follow the instructions provided in Setting up Bluetooth application note if a local interface is not detected by hcitool.

  2. Check a local interface status and switch it on if it is disabled:

    Code Block
    user@imx8mpnavq:~$ sudo hciconfig -a hci0
hci0:	Type: Primary  Bus: UART
	BD Address: D4:53:83:C4:E5:5B  ACL MTU: 1016:5  SCO MTU: 60:12
	UP RUNNING 
	RX bytes:1393 acl:0 sco:0 events:64 errors:0
	TX bytes:3256 acl:0 sco:0 commands:64 errors:0

user@imx8mpnavq:~$ sudo hciconfig hci0 up

3. Scanning for Remote Devices and Pairing

The default device name in the ml_ble_platform/sensor_base demo is AZN1-EVB. This name can be changed in the source files or by sending a command over BLE.

3.1. Scanning for Remote Devices with hcitool

Run sudo hcitool lescan to start scanning for LE devices:

Code Block
user@imx8mpnavq:~$ sudo hcitool lescan
LE Scan ...
...
C4:19:D1:52:01:4F AZN1-EVB

3.2. Scanning for Remote Devices and Pairing Using bluetoothctl

  1. Open bluetoothctl:

    Code Block
    user@imx8mpnavq:~$ bluetoothctl 
Agent registered
[CHG] Controller D4:53:83:C4:E5:5B Pairable: yes
[bluetooth]#

  2. Scan for available remote devices with the scan le command:

    Code Block
    [bluetooth]# scan le
Discovery started
[CHG] Controller D4:53:83:C4:E5:5B Discovering: yes
...
[NEW] Device C4:19:D1:52:01:4F AZN1-EVB

    The list of remote devices can be printed using the devices command:

    Code Block
    [bluetooth]# devices
... 
Device C4:19:D1:52:01:4F AZN1-EVB
...

  3. Use the pair <BD address> command to initiate pairing:

    Code Block
    [bluetooth]# pair C4:19:D1:52:01:4F
Attempting to pair with C4:19:D1:52:01:4F
[CHG] Device C4:19:D1:52:01:4F Connected: yes
[AZN1-EVB]#
...
[CHG] Device C4:19:D1:52:01:4F UUIDs: 00001800-0000-1000-8000-00805f9b34fb
[CHG] Device C4:19:D1:52:01:4F UUIDs: 00001801-0000-1000-8000-00805f9b34fb
[CHG] Device C4:19:D1:52:01:4F UUIDs: 0000180a-0000-1000-8000-00805f9b34fb
[CHG] Device C4:19:D1:52:01:4F UUIDs: 0000180f-0000-1000-8000-00805f9b34fb
[CHG] Device C4:19:D1:52:01:4F UUIDs: 242b0000-3f36-45ef-bb6b-6b0e778eb823
[CHG] Device C4:19:D1:52:01:4F UUIDs: 563b1512-179d-11eb-af7d-e30cfa630c08
[CHG] Device C4:19:D1:52:01:4F ServicesResolved: yes
[CHG] Device C4:19:D1:52:01:4F Modalias: usb:v248Ap8266d0001
[CHG] Device C4:19:D1:52:01:4F Paired: yes
Pairing successful

4. Communicating with the BLE Demo

4.1. Communicating with the BLE Demo Using gatttool in an Interactive Mode

  1. Open gatttool in an interactive mode:

    Code Block
    user@imx8mpnavq:~$ sudo gatttool -b C4:19:D1:52:01:4F --interactive
[C4:19:D1:52:01:4F][LE]>

  2. Connect to the device:

    Code Block
    [C4:19:D1:52:01:4F][LE]> connect
Attempting to connect to C4:19:D1:52:01:4F
Connection successful

  3. The characteristics list can be printed using the characteristics command:

    Code Block
    [C4:19:D1:52:01:4F][LE]> characteristics 
handle: 0x0002, char properties: 0x12, char value handle: 0x0003, uuid: 00002a00-0000-1000-8000-00805f9b34fb
handle: 0x0004, char properties: 0x02, char value handle: 0x0005, uuid: 00002a01-0000-1000-8000-00805f9b34fb
handle: 0x0006, char properties: 0x02, char value handle: 0x0007, uuid: 00002a04-0000-1000-8000-00805f9b34fb
handle: 0x0009, char properties: 0x20, char value handle: 0x000a, uuid: 00002a05-0000-1000-8000-00805f9b34fb
handle: 0x000d, char properties: 0x02, char value handle: 0x000e, uuid: 00002a50-0000-1000-8000-00805f9b34fb
handle: 0x0010, char properties: 0x12, char value handle: 0x0011, uuid: 00002a19-0000-1000-8000-00805f9b34fb
handle: 0x0014, char properties: 0x08, char value handle: 0x0015, uuid: 813dd366-179e-11eb-b214-a3729d689162
handle: 0x0016, char properties: 0x10, char value handle: 0x0017, uuid: 89accce6-179e-11eb-a4b6-e3d7b2402624
handle: 0x0019, char properties: 0x10, char value handle: 0x001a, uuid: a366b5cc-284a-11eb-b543-2766e21b935f
handle: 0x001c, char properties: 0x10, char value handle: 0x001d, uuid: 110d8470-2eb3-11eb-bf0c-8ff42f5dc2bc
handle: 0x001f, char properties: 0x08, char value handle: 0x0020, uuid: 773d9c12-efb8-44e8-bcc7-3e60e6fabd3a
handle: 0x0022, char properties: 0x22, char value handle: 0x0023, uuid: 242b0001-3f36-45ef-bb6b-6b0e778eb823
handle: 0x0025, char properties: 0x10, char value handle: 0x0026, uuid: 242b0002-3f36-45ef-bb6b-6b0e778eb823
handle: 0x0028, char properties: 0x0a, char value handle: 0x0029, uuid: 242b0003-3f36-45ef-bb6b-6b0e778eb823

  4. To send commands to the target, write to the TX characteristic using the char-write-req or the char-write-cmd command. A response from the demo is received as a notification on RX characteristic value change.
    To read a device name send the sys device-name=? command:

    Code Block
    [C4:19:D1:52:01:4F][LE]> char-write-req 0x15 737973206465766963652d6e616d653d3f0a
Characteristic value was written successfully
Notification handle = 0x0017 value: 40 31 32 35 37 36 32 32 3a 73 79 73 20 64 65 76 69 63 65 2d 6e 61 6d 65 3d 3f 0a 
Notification handle = 0x0017 value: 40 31 32 35 37 36 32 32 3a 44 65 76 69 63 65 20 6e 61 6d 65 20 69 73 20 41 5a 4e 31 2d 45 56 42 0a

    To set a new name use the sys device-name=<new name> command.

    To enable IMU sample streaming send the acc set_config, acc stream-on, and acc stream-on commands:

    Code Block
    [C4:19:D1:52:01:4F][LE]> char-write-req 0x15 616363207365745f636f6e6669670a
Characteristic value was written successfully
Notification handle = 0x0017 value: 40 31 33 34 30 32 37 32 3a 61 63 63 20 73 65 74 5f 63 6f 6e 66 69 67 0a 
Notification handle = 0x0017 value: 61 63 63 20 73 74 61 74 65 20 32 2c 20 63 61 6c 6c 62 61 63 6b 20 30 78 30 0a 
Notification handle = 0x0017 value: 40 31 33 34 30 32 37 32 3a 61 63 63 20 73 65 74 74 69 6e 67 20 63 6f 6e 66 69 67 2e 2e 2e 0a 
Notification handle = 0x0017 value: 73 65 6e 73 6f 72 20 30 20 63 6f 6e 66 69 67 65 64 0a 
[C4:19:D1:52:01:4F][LE]> char-write-req 0x15 6163632073746172740a
Characteristic value was written successfully
Notification handle = 0x0017 value: 40 31 33 39 39 39 38 35 3a 61 63 63 20 73 74 61 72 74 0a 
Notification handle = 0x0017 value: 73 6d 67 20 61 64 64 20 34 35 34 63 20 74 6f 20 30 0a 
Notification handle = 0x0017 value: 73 65 6e 73 6f 72 20 30 20 73 65 74 74 69 6e 67 20 63 6f 6e 66 69 67 0a 
Notification handle = 0x0017 value: 73 65 6e 73 6f 72 20 30 20 63 6f 6e 66 69 67 65 64 0a 
Notification handle = 0x0017 value: 40 31 33 39 39 39 39 30 3a 73 65 6e 73 6f 72 20 30 20 73 74 61 72 74 65 64 0a
[C4:19:D1:52:01:4F][LE]> char-write-req 0x15 6163632073747265616d2d6f6e0a
Characteristic value was written successfully
Notification handle = 0x0017 value: 40 31 34 37 37 39 30 30 3a 61 63 63 20 73 74 72 65 61 6d 2d 6f 6e 0a 
Notification handle = 0x0017 value: 40 31 34 37 37 39 30 30 3a 61 63 63 20 73 74 72 65 61 6d 69 6e 67 20 65 6e 61 62 6c 65 64 2e 2e 2e 0a 
Notification handle = 0x0017 value: 67 61 70 20 69 6e 20 73 65 6e 73 6f 72 20 30 20 73 65 71 5f 6e 6f 20 66 72 6f 6d 20 30 20 74 6f 20 34 30 35 30 0a

    After that notifications with IMU samples are being received:

    Code Block
    Notification handle = 0x001d value: 8e 87 16 00 a4 1f 36 1f 00 51 f9 ff c4 00 00 fe 01 00 
Notification handle = 0x001d value: a0 87 16 00 a6 1f 35 1f 00 58 f9 ff 8f 00 00 fe 01 00 
Notification handle = 0x001d value: b2 87 16 00 a8 1f 3d 1f 00 81 f9 ff 99 00 00 fe 01 00 
Notification handle = 0x001d value: c4 87 16 00 aa 1f 7d 1f 00 6b f9 ff 9e 00 00 02 02 00 
Notification handle = 0x001d value: d6 87 16 00 ac 1f 3d 1f 00 74 f9 ff c2 00 00 fe 01 00 
Notification handle = 0x001d value: e8 87 16 00 ae 1f 6b 1f 00 44 f9 ff 9b 00 00 02 02 00 
Notification handle = 0x001d value: fa 87 16 00 b0 1f 2d 1f 00 75 f9 ff 7c 00 00 fd 01 00 
Notification handle = 0x001d value: 0c 88 16 00 b2 1f 57 1f 00 40 f9 ff b3 00 00 01 02 00 
Notification handle = 0x001d value: 1e 88 16 00 b4 1f 4d 1f 00 5a f9 ff ab 00 00 00 02 00 
Notification handle = 0x001d value: 30 88 16 00 b6 1f 5b 1f 00 6e f9 ff 8f 00 00 00 02 00 
Notification handle = 0x001d value: 42 88 16 00 b8 1f 67 1f 00 5d f9 ff a2 00 00 01 02 00 
Notification handle = 0x001d value: 54 88 16 00 ba 1f 5a 1f 00 5f f9 ff 93 00 00 00 02 00 
Notification handle = 0x001d value: 66 88 16 00 bc 1f 6b 1f 00 35 f9 ff a6 00 00 02 02 00 
Notification handle = 0x001d value: 78 88 16 00 be 1f 54 1f 00 5b f9 ff 9f 00 00 00 02 00

    In the notification value the first 4 bytes are a timestamp, the next 2 bytes are a sequence number and the last 12 bytes are IMU samples.

4.2. Communicating with the BLE Demo Using gatttool in a Non-Interactive Mode

In a non-interactive mode gatttool connects to the target automatically, executes a requested command, and disconnects from the target.

...

Code Block
user@imx8mpnavq:~$ sudo gatttool -b C4:19:D1:52:01:4F --char-write-req -a 0x15 -n 616363207365745f636f6e6669670a
user@imx8mpnavq:~$ sudo gatttool -b C4:19:D1:52:01:4F --char-write-req -a 0x15 -n 6163632073747265616d2d6f6e0a
user@imx8mpnavq:~$ sudo gatttool -b C4:19:D1:52:01:4F --char-write-req -a 0x15 -n 6163632073746172740a
user@imx8mpnavq:~$ sudo gatttool -b C4:19:D1:52:01:4F --char-write-req -a 0x15 -n 00 --listen
Notification handle = 0x001d value: f4 b7 1c 00 9c c7 7c 1f 00 58 f9 ff ba 00 00 03 02 00 
Notification handle = 0x001d value: 06 b8 1c 00 9e c7 2a 1f 00 58 f9 ff b0 00 00 fd 01 00 
Notification handle = 0x001d value: 18 b8 1c 00 a0 c7 40 1f 00 60 f9 ff 99 00 00 ff 01 00 
Notification handle = 0x001d value: 2a b8 1c 00 a2 c7 5b 1f 00 67 f9 ff a4 00 00 00 02 00 
Notification handle = 0x001d value: 3c b8 1c 00 a4 c7 63 1f 00 84 f9 ff af 00 00 00 02 00 
Notification handle = 0x001d value: 4e b8 1c 00 a6 c7 71 1f 00 53 f9 ff b9 00 00 02 02 00 
Notification handle = 0x001d value: 60 b8 1c 00 a8 c7 7b 1f 00 5b f9 ff bd 00 00 02 02 00 
Notification handle = 0x001d value: 72 b8 1c 00 aa c7 44 1f 00 6b f9 ff 97 00 00 ff 01 00 
Notification handle = 0x001d value: 84 b8 1c 00 ac c7 49 1f 00 54 f9 ff 94 00 00 ff 01 00

Note: To send a command convert it to a hex-string without any quotes or the 0x prefix. Gatttool outputs also receive notification values as hex value arrays.

4.3. Useful Commands

Here are some useful commands for communicating with BLE demo:

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