inav/docs/Looptime.md

Looptime / Control loop frequency

Looptime / Control loop frequency (how often PID controller is executed and data is passed to motors) in INAV depends on multiple settings.

More, with asynchronous gyro processing, not all tasks are executed in the same time. Depending on async_mode setting, there are following cases:

async_mode = NONE

Gyroscope sampling and filtering, Accelerometer sampling and filtering, Attitude computation and PID control loop are executed as single tasks and processed one after another.

gyro_sync	gyro_lpf	Control Loop Rate (actual looptime) [us]
OFF	any	looptime
ON	!= 256HZ	1000 * gyro_sync_denom
ON	= 256HZ	125 * gyro_sync_denom

async_mode = GYRO

In this mode, gyro sampling and filtering is decoupled from PID main loop and executed separately. In this mode, gyro_sync is forced and is always ON

gyro_lpf	Control Loop Rate [us]	Gyro looptime [us]
!= 256HZ	looptime	1000 * gyro_sync_denom
= 256HZ	looptime	125 * gyro_sync_denom

async_mode = ALL

In this mode, Gyroscope sampling and filtering, Accelerometer sampling and filtering, Attitude computation and PID control loop are decoupled and run as separate tasks.

gyro_lpf	Control Loop Rate [us]	Gyro looptime [us]	Accelerometer looptime [us]	Attitude looptime [us]
!= 256HZ	looptime	1000 * gyro_sync_denom	1000000 / acc_task_frequency	1000000 / attitude_task_frequency
= 256HZ	looptime	125 * gyro_sync_denom	1000000 / acc_task_frequency	1000000 / attitude_task_frequency