F28377 up-down pwm frequency incorrect

Faizan Bhatti

Hi,

I am working on the epwm_updown example for cpu1 for the delfino F28377, using the evaluation board. I am trying to generate a 40KHz pwm signal by setting the TBPERIOD register to a value of 2500. However doing this generates a signal of 20KHz.

I have changed the counter mode to up count but the problem still exists.

Any help would be appreciated.

Faizan

over 12 years ago

0 Christian Ekman over 12 years ago

Intellectual 340 points

Remember that when you're using the up/down counter mode then you need to use the formula (2D)/SYSCLKOUT = 1/freq. So the TBPRD you need to set is:

D = SYSCLKOUT(2*freq), where freq is your desired output. Just a thought. Hope it helps!

What SYSCLKOUT do you have btw? Have you scaled it for the PWM module?

0 Faizan Bhatti over 12 years ago in reply to Christian Ekman

Prodigy 190 points

Hi Christian,

I am using the formula for TBPRD that you suggested. SYSCLKOUT is 200MHz and I am setting the EPWMCLKDIV bit to zero, so that the clock going into the pwm module is SYSCLK/ 1.

Faizan

0 Faizan Bhatti over 12 years ago in reply to Faizan Bhatti

Prodigy 190 points

The problem has been fixed. The issue was that the max input frequency that the pwm module accepts is 100MHz, whereas I was giving it an input of 200MHz.

Faizan

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F28377 up-down pwm frequency incorrect