I tried to use FFT in Mission Planner 1.3.49 with my Pixhack with ArduPlane 3.8.0 and ArduCopter 3.5.2 (tried both) and no one was successful. When I tried to use "Run all imus ACC GYR MSG" or "Run Log - imu 1 ACC GYR MSG" I got error message and When I try "Run all imus IMUI1-3" I got no reaction at all. My LOG_BITMASK is 655358 "All+Full IMU" and Log graph shows it well.
Is there any requirements/restrictions for logs to show FFT graphs? Do I need only 3 imu turned on log to get it working? Should it be minimum run time for log to run properly?