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]

Hi, Sorry for the late update. I followed this tutorial and created a program. It compiles without error. But the device is not advertising. In the debug, I found this error, eror_code=0x00000004

I saw it as a memory error from this video. I enabled the nrf_log_enabled and nrf_log_backed_rtt to see the debug terminal. But I can't see anything in the terminal. How can I fix this issue? If you want additional information, please let me know.

[Jørgen Holmefjord]

Hi,

Try increasing NRF_SDH_BLE_VS_UUID_COUNT in your sdk_config.h file. Regarding logging, have you enabled the logger module through NRF_LOG_ENABLED config in your sdk_config.h file?

You also have to call the init macro in main(): NRF_LOG_INIT(NULL);, and you may have to call NRF_LOG_DEFAULT_BACKENDS_INIT(). More details can be found in the Logger module documentation.

Best regards,
Jørgen

[Karthiknk]

Thank you, sure I will go through the material. I followed this tutorial about the adjustment of flash and RAM memory. When I change to debugger recommended RAM start, then the RAM_START +  RAM_SIZE is larger than RAM_PH_START + RAM_PH_SIZE. 

What should I do now? I'm stuck.

[Jørgen Holmefjord]

You need to adjust the size to match the size of the RAM available in the chip you are using. If you increase the RAM start address, you need to decrease the size accordingly.

[Karthiknk]

I made the Debug terminal to work. I changed the RAM start address as recommended. Still, I get Fatal error. unsigned int error_code=0x00000004. This is what I get in the Debug 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 0x20002250
<error> app: Fatal error

[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?