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Hi,
I set default clock to 200 MHz with predefined symbol _LAUNCHXL_F28379D. I set EPWM_TIMER_TBPRD =2. When I run this code:
EPWM_setTimeBasePeriod(base, EPWM_TIMER_TBPRD);
EPWM_setPhaseShift(base, 0U);
EPWM_setTimeBaseCounter(base, 0U);
EPWM_setTimeBaseCounterMode(base, EPWM_COUNTER_MODE_UP);
EPWM_disablePhaseShiftLoad(base);
//
// Set ePWM clock pre-scaler
//
EPWM_setClockPrescaler(base,EPWM_CLOCK_DIVIDER_1, EPWM_HSCLOCK_DIVIDER_1);
EPWM_setActionQualifierAction(base,
EPWM_AQ_OUTPUT_A,
EPWM_AQ_OUTPUT_TOGGLE,
EPWM_AQ_OUTPUT_ON_TIMEBASE_PERIOD);
EPWM_setActionQualifierAction(base,
EPWM_AQ_OUTPUT_B,
EPWM_AQ_OUTPUT_TOGGLE,
EPWM_AQ_OUTPUT_ON_TIMEBASE_ZERO);
on the scope the meander frequency is 16.68 MHz and A and B outputs are not out of phase but shifted pi/2. I would expect the frequency to be half of 200 MHz clock.
thanks vadim
Hi Vadim,
200Mhz is the speed of the PLLSYSCLK with default configuration. The TBCLK is 100 MHz if you're using default clock configurations.
200Mhz / 2 = 100Mhz, and you're using HSPCLKDIV = /1 , and CLKDIV = /1, thus giving a 100Mhz signal
The frequency is correct since you are toggling at the end of the period. Instead if you toggled at CMPA event, you will get a frequency of 33.33Mhz.
I have outputted the waveforms between A and B as shown. A is toggling when CMPA = 1, B is toggling when the period comes. Output A is giving a 33.3Mhz output, and output B is giving a 16.68Mhz output.
If you want a 100Mhz signal, you will have to change the clock configuration so that your TBCLK is running at 200Mhz. However according the datasheet you can have a max EPWMCLK frequency of 100Mhz.
Hi Ryan,
I followed your suggestions but still get the same result.
Here is the code:
void initEPWMWithoutDB(uint32_t base)
{
//
// Set-up TBCLK
//
EPWM_setTimeBasePeriod(base, 2);
EPWM_setPhaseShift(base, 0U);
EPWM_setTimeBaseCounter(base, 0U);
EPWM_setTimeBaseCounterMode(base, EPWM_COUNTER_MODE_UP);
EPWM_disablePhaseShiftLoad(base);
EPWM_setCounterCompareValue(myEPWM1_BASE, EPWM_COUNTER_COMPARE_A, 1);
//
// Set ePWM clock pre-scaler
//
EPWM_setClockPrescaler(base,EPWM_CLOCK_DIVIDER_1, EPWM_HSCLOCK_DIVIDER_1);
EPWM_setActionQualifierAction(base,
EPWM_AQ_OUTPUT_A,
EPWM_AQ_OUTPUT_TOGGLE,
EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPA);
EPWM_setActionQualifierAction(base,
EPWM_AQ_OUTPUT_B,
EPWM_AQ_OUTPUT_TOGGLE,
EPWM_AQ_OUTPUT_ON_TIMEBASE_PERIOD);
}
thanks vadim
