Unless you added an external SD adapter, that autopilot doesn’t look like it supports logging. So whatever file you have probably isn’t a .bin log suitable for analysis.
Thank you for response. I have 4 such FC (CC3D Revolution), and they all support logging, as I had successfully downloaded the DF files
from these FCs, both in Arduplane and Arducopter FW. Occasionally downloading fail because of unknown reasons, though all the values
in LOG parameters in all these 4 FCs are the same. This situation has been going on for a couple of years.
Very often, without me changing any setting on a FC which has been logging successfully, that FC suddenly fails to log, or it fails to download the DF files…
This Flight controller is one of the Open Hardware supported by Ardupilot. Since I have 4 of them, I naturally use them and they
have been performing well, including logging in most cases, as long as LOG_BACKEND_TYPE is set to 4 (for BLOCK).