topic Re: MCXN SCTIMER in MCX Microcontrollers

MCXN SCTIMER

Vagni — Wed, 30 Oct 2024 08:59:18 GMT

I successfully run the SDK sctimer_pwm_with_dutycycle_change example program on the MCX-N5XX-EVK board. I successfully changed the PWM mode from Center-Aligned to Edge-Aligned.

But I get the following issues:

The SCT outputs a short high impulse when I set 0% duty cycle.
The SCT outputs a short low impulse when I set 100% duty cycle.
In addition to the dudty cycle, I also need to change the PWM frequency run-time, so I tried to re-configure the PWM with my following function:

short PWM_FreqSet( unsigned long pwmFreq_Hz, unsigned char duty) { short RetVal = 0; sctimer_pwm_signal_param_t pwmParam; uint32_t sctimerClock = SCTIMER_CLK_FREQ; /* Stop the 32-bit unify timer */ SCTIMER_StopTimer(SCT0, kSCTIMER_Counter_U); /* Configure PWM with the new frequency */ pwmParam.output = DEMO_SCTIMER_OUT; pwmParam.level = kSCTIMER_HighTrue; pwmParam.dutyCyclePercent = duty; if (SCTIMER_SetupPwm(SCT0, &pwmParam, kSCTIMER_EdgeAlignedPwm, pwmFreq_Hz, sctimerClock, &eventNumberOutput) == kStatus_Success) { RetVal = 1; /* Start the 32-bit unify timer */ SCTIMER_StartTimer(SCT0, kSCTIMER_Counter_U); } return RetVal; }

But it does not work, although SCTIMER_SetupPwm() returns kStatus_Success. And, after the first calling to my PWM_FreqSet() function, the PWM timer does not work any more, I need to reset my board to recover it.

How to fix those issues on SCTIMER?

Re: MCXN SCTIMER

Harry_Zhang — Fri, 01 Nov 2024 04:14:22 GMT

Hi @Vagni

1. When setting 0% duty cycle or 100% duty cycle, This can be done by bypassing the PWM setup logic and directly setting output pin high.

2. I try to change PWM Frequency at Runtime.

/* Configure first PWM with frequency 24kHZ from first output */ pwmParam.output = DEMO_FIRST_SCTIMER_OUT; pwmParam.level = kSCTIMER_HighTrue; pwmParam.dutyCyclePercent = 50; if (SCTIMER_SetupPwm(SCT0, &pwmParam, kSCTIMER_CenterAlignedPwm, 48000U, sctimerClock, &event) == kStatus_Fail) { return -1; } /* Start the 32-bit unify timer */ SCTIMER_StartTimer(SCT0, kSCTIMER_Counter_U); SCTIMER_StopTimer(SCT0, kSCTIMER_Counter_U); /* Configure PWM with the new frequency */ pwmParam.output = DEMO_FIRST_SCTIMER_OUT; pwmParam.level = kSCTIMER_HighTrue; pwmParam.dutyCyclePercent = 50; if (SCTIMER_SetupPwm(SCT0, &pwmParam, kSCTIMER_CenterAlignedPwm, 24000U, sctimerClock, &event) == kStatus_Fail) { return -1; } SCTIMER_StartTimer(SCT0, kSCTIMER_Counter_U);

It can work.

Hang

Re: MCXN SCTIMER

Vagni — Sun, 03 Nov 2024 17:07:17 GMT

Thank you, Hang.

Your code is pretty much the same as mine, unless you use Center-Aligned PWM mode and the same dutycycle value when you change the PWM frequency.

Maybe changing the PWM frequency at run-time is possible only with the current dutycycle value?

What about the 'event' variable? It needs to be cleared before changing the PWM frequency at run-time?

Re: MCXN SCTIMER

Harry_Zhang — Tue, 05 Nov 2024 02:51:57 GMT

Hi @Vagni

1. Maybe changing the PWM frequency at run-time is possible only with the current dutycycle value?

Yes

2. What about the 'event' variable? It needs to be cleared before changing the PWM frequency at run-time?

I test it, i change the PWM frequency at run-time directly, it can work.

Hang