It sounds like you’ve got most of the setup working correctly since you can stream sensor data over Bluetooth and see the headers on the SD card. The fact that the file is created but no data is written usually points to a few common issues in the setup:
Recording not enabled – In the default AppPro or your modified application, make sure that the data logging function is actually started after initialization. Sometimes the file is created immediately, but writing only starts after you explicitly start the recorder.
Buffering or flush issues – The data recorder often stores data in a buffer before writing it to the SD card. If the buffer isn’t flushed correctly, the file may remain empty. Ensure the code periodically calls the flush function or stops properly to finalize the file.
SD card format or permissions – Even if it’s the ST-provided card, check that it’s formatted correctly (usually FAT32) and is not write-protected. Also, confirm that the board recognizes it fully.
Data source configuration – Verify that the sensors are linked to the recorder. If you can stream them via Bluetooth but haven’t added them to the recorder’s sensor list, no data will be saved even though the header exists.
Power or timing issues – Some evaluations show that if the board resets or the application hasn’t waited long enough for initialization, the recorder may miss the first data samples.
A practical way to debug: start with one sensor, confirm data is written, then add others incrementally. Also, check the application log (if available) for any SD write errors.
Most often, the issue is just that the recorder isn’t actually started or the flush isn’t called, so the file remains empty.
