I want to control the frequency of PWM accurately.

[schosdas]

Hello

I'm testing multiple frequencies to ensure smooth ultrasound control.

Frequency can be generated via 'APP_PWM_DEFAULT_CONFIG_1CH (period, pin)'.  But it seems difficult to use this to output more accurate frequencies.

For example, if I use that function to put 10 in the period value, 100 kHz is output, and if I put 9 in, 111 kHz is output. What should I do to print the value between them here?
I need detailed frequency output.

Thank you.

[Karl Ylvisaker]

Hello,

The PWM library only provides micro-second resolution of the output PWM.
The APP_PWM_DEFAULT_CONFIG_1CH takes the period_in_us argument to set the period.
This is why you are seeing a 100 kHz PWM when you provide it 10, and a 111 kHz PWM when you provide it 9.
1/0.00001 = 100 kHz, 1/0.000009 = 111 kHz.

If you need to control the period more accurately, you will have to use peripheral driver with the approach I described to you in your other ticket yesterday.

Best regards,
Karl

[schosdas]

Thank you for your answer.
I succeeded in outputting the frequency through Prescaler and top_value of pwm_driver.

[Karl Ylvisaker]

schosdas said:

Thank you for your answer.

No problem at all, I am happy to help! 

schosdas said:

I succeeded in outputting the frequency through Prescaler and top_value of pwm_driver.

I am glad to hear that you were able to achieve the desired frequency by my suggestion using the PWM driver :) 

Please do not hesitate to open a new ticket if you should encounter any other issues or questions.

Good luck with your development!

Best regards,
Karl