The in-flight noise analyser (FFT) is not ready

What ArduPilot says:

• FFT: resolution is N.NHz, increase length
• FFT config MAXHZ NHz > NHz
• FFT calibrating noise
• FFT: self-test failed: wanted N.N, had N.N
• FFT self-test failed, max error N.NHz
• FFT still analyzing

With FFT_ENABLE 1 the flight controller analyses the gyro signal in flight to find the frequency of the motors' noise for the notch filter. Before the first arming it measures the noise floor and tests itself on known frequencies; arming waits for that. “FFT calibrating noise” and “FFT still analyzing” are the wait. “FFT config MAXHZ” means FFT_MAXHZ is above half the rate the FFT samples at. “self-test failed” means it missed a test frequency by too much. “FFT: calibrated” is success: sample rate, frequency resolution and update rate.

What to do, most likely first

1. The analyser is still measuring its noise floor after power-on.

   FixKeep the aircraft still for a few seconds and try again; “FFT: calibrated” tells you it is done.

2. FFT_MAXHZ is too high for the rate the gyro is sampled at.

   Check“FFT config MAXHZ” gives both numbers: yours first, the limit second.

   FixSet FFT_MAXHZ at or below the second number and reboot.

3. The self-test fails: the FFT settings do not suit this board.

   Check“FFT: resolution is … increase length” may come first: with a resolution coarser than 50 Hz the window is too short.

   FixSet FFT_WINDOW_SIZE, FFT_MINHZ, FFT_MAXHZ and FFT_SAMPLE_MODE back to their defaults and reboot. If the test still fails, this board cannot run the FFT: drive the notch filter from throttle or ESC RPM and set FFT_ENABLE to 0.

These lines are tagged as INS failures, but they belong to the FFT group of arming checks.

Parameters to look at

Where to do it:Setup & Tuning Guide