Hi Rabbit,
SlaveFrequencyCalibration() is used to measures break impulse from PC and sets correct trim value, it firstly set UART RX pin as GPIO function and wait for the falling edge on it and then start to count the systick with the help of systick timer till it observes a rising edge on that pin, then it uses the result to calculate the trim value, but as the device doesn't support float point, so the final value might have some offset in some cases.
Please kindly let me know if you have any further question.
Have a nice day!!
B.R
Kan
