topic FTM CnV Update Problem 2 in Kinetis Microcontrollers

FTM CnV Update Problem 2

Jana_muralidharan — Mon, 22 Dec 2025 08:31:47 GMT

Hi, I got another problem, i previously ask and got solve it is the LDOK register that i was wrong

but even after solving that it still not doing what i ask that is to update the CnV and change the Pulse width please help me this is that code i have been working on

#include "MKE02Z4.h" #define FTM_MOD 24 // 25 ticks → 1.25us @ 20MHz #define TICKS_0 7 #define TICKS_1 14 void FTM_Init(void) { SIM->SCGC |= SIM_SCGC_FTM2_MASK; FTM2->MODE = FTM_MODE_WPDIS_MASK | FTM_MODE_FTMEN_MASK; FTM2->CNTIN = 0; FTM2->CNT = 0; FTM2->MOD = FTM_MOD; FTM2->CONTROLS[0].CnSC = FTM_CnSC_MSB_MASK | FTM_CnSC_ELSB_MASK; FTM2->CONTROLS[0].CnV = TICKS_0; /* ENABLE CHANNEL OUTPUT (CRITICAL) */ FTM2->OUTMASK &= ~(1 << 0); /* Initial load */ *(volatile __UINT32_TYPE__ *)0x4003A098 = 0x0201; FTM2->SC = FTM_SC_CLKS(1) | FTM_SC_PS(0); *(volatile __UINT32_TYPE__ *)0x4003A064 = 0x00; } static inline void wait_ftm_period(void) { while(!(FTM2->SC & FTM_SC_TOF_MASK)); FTM2->SC &= ~FTM_SC_TOF_MASK; } uint32_t word = 0x5555; int main(void) { FTM_Init(); while (1) { for(int i = 0; i < 16; i++) { if (word & (1UL << i)) *(volatile __UINT32_TYPE__ *)0x4003A010 = TICKS_1; else *(volatile __UINT32_TYPE__ *)0x4003A010 = TICKS_0; /* ARM reload for next PWM cycle */ *(volatile __UINT32_TYPE__ *)0x4003A098 = 0x0201; /* WAIT ONE PWM PERIOD */ wait_ftm_period(); } } }

Re: FTM CnV Update Problem 2

Jana_muralidharan — Mon, 22 Dec 2025 08:46:25 GMT

Hey I am the writer of the post And i am working in the WS2812B so i though of using PWM to generate the signal so that why thing thing of changing the Duty cycle so and i want to know Is it possible to do that with this

Re: FTM CnV Update Problem 2

Alice_Yang — Tue, 23 Dec 2025 02:33:34 GMT

Hi @Jana_muralidharan ]

I'm sorry, I'm a bit confused. Are you asking how to change the duty cycle of the PWM, or are you asking why your duty cycle changed?

Thank you.

Alice

Re: FTM CnV Update Problem 2

Jana_muralidharan — Wed, 24 Dec 2025 06:50:48 GMT

Hello @Alice_Yang,
Yeah i am trying to change the PWM duty cycle for every cycle like for 1st period 30% duty cycle then in the 2nd period 70% duty cycle like that

Is there any procedure to change the PWM duty change

It just stuck at the initially set value that the issue here

Re: FTM CnV Update Problem 2

Alice_Yang — Wed, 24 Dec 2025 10:08:16 GMT

Hello @Jana_muralidharan

Please use the FTM_UpdatePwmDutycycle() API to update the PWM duty cycle.

For more details, refer to the ftm_simple_pwm demo, where the PWM duty cycle is periodically updated.

/*!
 * brief Updates the duty cycle of an active PWM signal.
 *
 * param base FTM peripheral base address
 * param chnlNumber The channel/channel pair number. In combined mode, this represents
 * the channel pair number
 * param currentPwmMode The current PWM mode set during PWM setup
 * param dutyCyclePercent New PWM pulse width; The value should be between 0 to 100
 * 0=inactive signal(0% duty cycle)...
 * 100=active signal (100% duty cycle)
 * return kStatus_Success if the PWM update was successful
 * kStatus_Error on failure
 */
status_t FTM_UpdatePwmDutycycle(FTM_Type *base,
ftm_chnl_t chnlNumber,
ftm_pwm_mode_t currentPwmMode,
uint8_t dutyCyclePercent)
 

Alice

Re: FTM CnV Update Problem 2

Jana_muralidharan — Fri, 26 Dec 2025 04:32:42 GMT

But can you please tell me, in how much cycle that the PWM updates

Re: FTM CnV Update Problem 2

Alice_Yang — Fri, 26 Dec 2025 07:03:30 GMT

Hello @Jana_muralidharan

This depends on your application. You can refer to your requirement design.

Regarding this SDK demo, it uses a timer overflow interrupt to update the PWM duty cycle.

Alice