BLE accelerometer

[Karthiknk]

Greetings,

I'm using nRF52 DK to transfer LIS3DH accelerometer data in Bluetooth. I successfully managed to establish an I2C connection with my sensor, I get my XYZ values. Now I want to send the data in Bluetooth, I'm a bit confused about what to do next. Is there any example program in SDK that will help me? or if you can suggest to me some tutorial that would be helpful too. I'm a beginner, so any advice or suggestions are welcome. Thank you.

[Jørgen Holmefjord]

Hi,

It is possible to send the values as a string using Nordic UART Service (NUS). There is an example available in the SDK: UART/Serial Port Emulation over BLE

If you want to create your own custom service for sending accelerometer data, please have a look at the BLE tutorials. These should be most useful:

• Bluetooth low energy Services, a beginner's tutorial
• Bluetooth low energy Characteristics, a beginner's tutorial

Best regards,
Jørgen

[Jørgen Holmefjord]

Do you get any error codes when calling ble_nus_data_send? Also, make sure that twim_handler does not run at a interrupt priority higher than 4, as this will prevent you from calling softdevice APIs.

[Karthiknk]

I fixed the RAM issue. The device is advertising. But it is not connecting. In nRF Connect app, I see not bonded. How can I fix it?

[Jørgen Holmefjord]

"Not bonded" and "not connected" are two different things. Do the phone try to connect, but fails? Are you seeing anything in the logs of nRF Connect application, or the peripheral device that indicates what goes wrong?

[Karthiknk]

The device is shown in scanner. I give connect. It opens up Nordic_template. I can not see anything in the client. 

[Jørgen Holmefjord]

Try dragging the empty client window towards the right side of the screen, that should reveal the log terminal. It may be that something crashes on the peripheral side during connection, leading to a reset or something. Does the log on the peripheral side not give any output regarding what happens?

[Karthiknk]

This is what I see in the debugger terminal.

<info> app_timer: RTC: initialized.
<debug> nrf_sdh: State request: 0x00000000
<debug> nrf_sdh: Notify observer 0x0003095C => ready
<debug> nrf_sdh: State change: 0x00000000
<debug> nrf_sdh: State change: 0x00000001
<debug> nrf_sdh_ble: RAM starts at 0x20002260
<info> app: Template example started.
<info> app: Fast advertising.

And in nRF connect log. I get error 133 (0x85): GATT ERROR

[Jørgen Holmefjord]

Are you checking error codes from all softdevice APIs you are calling in your application?

If you could provide a sniffer trace of the communication between the two devices, that could also help determining where the issue occurs.

[Karthiknk]

Are you checking error codes from all softdevice APIs you are calling in your application?

Yes I guess, I didn't change anything in the app_template example regarding error check. 

And in nRF connect log. I get error 133 (0x85): GATT ERROR

didn't this log information helps in any way?

[Jørgen Holmefjord]

Karthiknk said:

Are you checking error codes from all softdevice APIs you are calling in your application?

Yes I guess, I didn't change anything in the app_template example regarding error check. 

I was thinking more about the code that you added from the tutorial, that you have remembered to store the return code from all function calls, and pass this along to APP_ERROR_CHECK() macro.

Karthiknk said:

And in nRF connect log. I get error 133 (0x85): GATT ERROR

didn't this log information helps in any way?

Unfortunately, this is a very generic error code. It can be caused by a lot of things. Can you post the full log output from nRF Connect? A sniffer trace will also tell if the peripheral did not respond to packets, etc.

[Karthiknk]

Hi Jorgen. While setting up sniffer, programming my nRF52 DK, I accidentally put my DK in bootloader mode. How can I bring it back to normal? I can not see the device in nrf connect.

[Karthiknk]

Hi, I found the problem. The device is advertising, When I connect to the nRF Connect application, I can not see my service, the status says disconnected. 

This is the timer event handler I use in the program

static void timer_timeout_handler(void * p_context)
{
// Acquire accelerometer data
MPU6050_ReadAcc(AccValue); // accelerometer read
acc[0] = AccValue[0];
acc[1] = AccValue[1];
acc[2] = AccValue[2];

characteristic_accel_update(&m_our_service, acc);
}

If I  line comment my accelerometer read function, The app works fine, I can see the service and its characters at the nrf connect(without accel. values). How can I include my accelerometer read function into my program without crashing the app?