Fast PWMFast PWM works only on pin A0 (digital pin 3) and allows to run PWM on a higher frequency compared to that analogWrite() provides. Check Z-Uno pinout zunoFastPWMInit(prescale) prescale 0 for 4 MHz (timer tick is 0.25 μs) and ZUNO_GPT_SCALE1024 for 31.25 kHz (timer tick is 32 μs) none zunoFastPWMSet(low_ticks, high_ticks) low_ticks low level time in timer ticks. Ticks depend on the speed set by zunoFastPWMInit() high_ticks high level time in timer ticks. Ticks depend on the speed set by zunoFastPWMInit() none zunoFastPWMEnable(value) value FALSE to turn Fast PWM off and TRUE to turn on none After changing parameters of Fast PWM you need to disable and then enable PWM again.
Z-Uno2 doesn't implements this functions, because its builtin PWM controller supports wide range of carrier frequencies. You are able to archive "FastPWM" functionality using analogWrite and analogWriteFrequency functions.
pinMode(A0, OUTPUT); zunoFastPWMInit(0); // 0 for 4 MHz (tick is 0.25 μs) and ZUNO_GPT_SCALE1024 for 31.25 kHz (tick is 32 μs) zunoFastPWMSet(100, 100); // Low and high level time in timer ticks. zunoFastPWMEnable(1); // Start ... zunoFastPWMEnable(0); // Turn off once not needed anymore