Frequency change on cycle end.

[legitnoscam]

Hi, is there a way to change frequency of PWM only on rising or falling edge of the signal? If i do it like in the example:
`frequency = 1000.0f;

Serial.print(F("Change PWM Freq to "));
Serial.println(frequency);
PWM_Instance->setPWM(pinToUse, frequency, 50.0f);
printPWMInfo(PWM_Instance);

delay(2);

frequency = 10000.0f;

Serial.print(F("Change PWM Freq to "));
Serial.println(frequency);
PWM_Instance->setPWM(pinToUse, frequency, 50.0f);
printPWMInfo(PWM_Instance);`

then the frequency is "forced" to change.

[khoih-prog]

Hi @legitnoscam

Your description is not clear.

Is your issue similar to what was described in Changing Duty Cycle Dynamically Creates Runt PWM pulse #10 ?

[legitnoscam]

Thank you for your response. Yes, the issue is similar, the difference is that I am not changing the duty cycle (it is set to be 50%), im changing the frequency. The result is similar, a very small pulse is generated as seen on the picture. Im asking about this because in the LEDC documentation i read about fading which i understood to be HW based and was thinking this would not allow for something like this to happen.

The LEDC hardware provides the means to gradually transition from one duty cycle value to another. To use this functionality, enable fading with ledc_fade_func_install() and then configure it by calling one of the available fading functions:

The quote describes duty cycle change, but i was thinking similar thing is possible for the frequency.

The signal i want to generate is around 2.2 MHz so not every PWM library i found was able to handle that.

[khoih-prog]

Hi @legitnoscam

Please check the new ESP32_FastPWM v1.1.0 to see if the glitch has gone.

I've tried the best with my scope, but haven't seen the glitch yet.

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Releases v1.1.0

1. Add example PWM_manual to demo how to correctly use PWM to generate waveform. Check About DCValue in setPWM_manual #2
2. Add function setPWM_DCPercentage_manual() to facilitate the setting PWM DC manually by using DCPercentage, instead of absolute DCValue depending on varying resolution
3. Fix glitch when changing PWM frequency. Check Frequency change on cycle end. #1