Overview

The FREQ parameter group (often appearing as FFT_MAXHZ or MOT_PWM_FREQ) manages various frequency-domain settings across the autopilot.

Key Concepts

1. Vibration Tracking (FFT_...HZ)

Used by the in-flight FFT engine to bracket the expected motor noise.

• MAXHZ: The upper limit of the frequency sweep.

2. Motor PWM Frequency (MOT_PWM_FREQ)

(Often grouped here in documentation) Sets the update rate for the ESC signal.

• 490Hz: Standard for most PWM ESCs.
• 16kHz - 24kHz: Used for brushed motors or ultra-high-speed ESCs to reduce audible whine.

Parameter Breakdown

• FFT_MAXHZ: Upper bound for vibration analysis.
• MOT_PWM_FREQ: Output update rate.

Developer Notes

• Library: libraries/AP_InertialSensor (for FFT) or libraries/AP_Motors (for PWM).