Storing nrf_log output (NRF_LOG_INFO) in internal file system .

[xcepti0n]

Hi,

I am beginner in nordic development. I will be using using FreeRTOS with nordic ( if that matters).

Requirement: I need to store logs in internal file system.

Device - nrf52840 DK,

SDK - nRF5_SDK_15.3.0

I understand that nrf_log output is limited to backends - UART/RTT/CLI, But I want to log into a file in internal file system.

Please tell if more details are required.

[xcepti0n]

I have implemented (almost) a new backend which writes to file (fatfs). I want to use deferred mode so, do I need to implement my own circular buffer of it has been handled in the frontend? I have gone through the source code but seems like I have to implement it myself or am I missing something?

[Einar Thorsrud]

Hi,

The frontend has a circular buffer that buffers log messages until they are processed (m_log_data.buffer).

[xcepti0n]

Thanks for the reply. I also found out that its  NRF_LOG_FLUSH which in turns call nrf_log_backend_put() and eventually nrf_log_backend_flush() so what is actual purpose of nrf_log_backend_flush here? Please tell me if I have understood it wrong.

[Einar Thorsrud]

Hi,

nrf_log_backend_flush() is called from nrf_log_frontend_dequeue(), which is defined to NRF_LOG_INTERNAL_PROCESS(), which is called from NRF_LOG_INTERNAL_FLUSH(). This in turn is called from NRF_LOG_FLUSH() or NRF_LOG_INTERNAL_FINAL_FLUSH(). nrf_log_backend_flush() is not called from anywhere else.

The purpose of nrf_log_backend_flush() is to make the backend drop log messages in case they are not processed in time. The backend can simply use an empty implementation if this is not relevant (as is the case for most of the log backends in the SDK).