change frequency at runtime for PWM in mcuexpresso for FRDM-KL25Z

[tims123]

I wanted to change frequency of PWM at runtime to ramp the stepper motor.

I looked at various options like PPG, but its not available on mcuxpresso or i didn't find it. 

Please help.

[tims123]

Used Timers in my application for now. 

Implementing Frequency change in fsl_tpm.h API would be great though.

Closing the issue.

[kerryzhou]

Hi tims123

   Thanks for your updated information.

    Any new questions in the future, welcome to create the new question post!

Best Regards,

Kerry

[kerryzhou · Accepted solution]

Hi tims123

   Do you use the TPM to output the PWM?

   If yes, if you want to change the PWM frequency , you can change your TPMx_MOD, 

  More details, please check the KL25 reference manual:

https://www.nxp.com/docs/en/reference-manual/KL25P80M48SF0RM.pdf

 chapter 31.4.8.1 MOD Register Update

31.4.8.1 MOD Register Update
If (CMOD[1:0] = 0:0) then MOD register is updated when MOD register is written.
If (CMOD[1:0] ≠ 0:0), then MOD register is updated according to the CPWMS bit, that
is:
• If the selected mode is not CPWM then MOD register is updated after MOD register
was written and the TPM counter changes from MOD to zero.
• If the selected mode is CPWM then MOD register is updated after MOD register was
written and the TPM counter changes from MOD to (MOD – 1).

Wish it helps you!

If you still have questions about it, please kindly let me know!

Best Regards,

Kerry

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[tims123]

I'm using the fsl_tpm.h API, it has a method to update PWM duty cycle , but not Frequency or Time Period. will try updating MOD register and will let you know.

[kerryzhou]

HI tims123

   Ok, you can try it at first.

   Any updated information from your side, just feel free to let me know.

Best Regards,

Kerry