Understanding FTM CPWM

sean_dvorscak — Tue, 24 Jan 2023 17:44:38 GMT

I am looking for a better understanding to something that I am seeing from the PWM output on the FTM in Center Aligned PWM Mode.

From what I read in the reference manual, if the ELSB = 1, and ELSA = 0, then the FTM PWM is set on the channel match during the down count, and cleared on the channel match of the up count.

However, I see on the scope the PWM set on the channel match of the up count, and cleared on the channel match of the down count.

Here is a capture of the scope showing a 80% duty cycle pulse on FTM CH0 (shown in the bottom red Ch 7 on scope). The pink (Ch 2 on scope) are the INITTRIGs from the FTM when the FTM counter reaches 0 (CNTMIN = 1). As you can see, the pulse is centered around the MOD value of the FTM:

Here is my complete configuration, let me know if I am missing something with my current configuration of FTM3 that is making me misunderstand what I am doing(I know it shows CNTMAX instead of CNTMIN is set, but this is because I was doing other experiments when I took these pictures. No other configuration settings were changed for the scope picture):

Re: Understanding FTM CPWM

danielmartynek — Wed, 25 Jan 2023 10:14:24 GMT

Hello @sean_dvorscak,

I'm not able to replicate it.

Can you share the whole project so that I can test it on my side?

Thanks,

BR, Daniel

topic Understanding FTM CPWM in S32K

Understanding FTM CPWM

Re: Understanding FTM CPWM