Use timer`s chain to generate N impulse`s

[AlexKeisy]

I do some serial interface clock with timers chain on stm32f407.

Thats work, but generate little bit lower count of impulses. where is my trouble? len is about 16 384, overall pulse count len*16.

I miss about 200*16=3200 pulses.

Thank You!

TIM2->PSC=0;

  TIM2->ARR=3-1;//3 tact`s per pulse

TIM2->CCR2= 1;

  TIM2->CCER |= (TIM_CCER_CC2E);

  TIM2->CCMR1 &=~( TIM_CCMR1_OC2M_0);

  TIM2->CCMR1 |= ( TIM_CCMR1_OC2M_1 | TIM_CCMR1_OC2M_2);

  //TIM2 slave gate mode and source ITR3

  TIM2->SMCR &= ~(TIM_SMCR_SMS_Msk | TIM_SMCR_TS_Msk);

  TIM2->SMCR |= TIM_SMCR_SMS_0 | TIM_SMCR_SMS_2 | TIM_SMCR_TS_0 | TIM_SMCR_TS_1;

// TIM4 up counting mode, pulse width to TRGO

// Prescaler = 3_tact`s_per_pulse * 16_bits_per_Word -1

TIM4->PSC = 3*16 -1;

TIM4->ARR = len;

TIM4->CR1 &= ~(TIM_CR1_ARPE_Msk | TIM_CR1_CKD_Msk | TIM_CR1_CMS_Msk | TIM_CR1_DIR_Msk);

TIM4->CR1 |= TIM_CR1_OPM ;

TIM4->CR2 &= ~(TIM_CR2_CCDS_Msk | TIM_CR2_MMS_Msk | TIM_CR2_TI1S_Msk);

TIM4->CR2 |= TIM_CR2_MMS_0;

//reset counters

TIM4->EGR |= TIM_EGR_UG;

TIM2->CR1 |= TIM_CR1_CEN;

TIM4->CR1 |= TIM_CR1_CEN;

while (TIM4->CR1 & TIM_CR1_CEN){

cntr++;

}

[AlexKeisy]

Maybe is there another way to do that!?

[TDK]

What is your timer clock speed and how are you measuring pulses? By my count, you are generating 262160 pulses. Switching PWM output every 1-2 cycles might produce a signal without a very good edge.

Might be easier to diagnose if you reduced the number of pulses to something easily viewed on a scope. Say 8. Then, once that's working, scale up to what you really want.

You probably want "TIM4->ARR = len -1;" but that couldn't be the issue.

Could use SPI_SCK to output pulses but only if it fits with your clock.

[AlexKeisy]

Thank You For Interest!

I found if len below than 208 no impulses. correct count of impulses generated if use len+208

168 MHz CPu, 84 MHz AHB2, 84/3 to out, its work stable, but what is 208?

timer state before start with

TIM4->ARR = 128*20+208;

[TDK]

Set TIM4->CNT to 0 before you start it. It could be starting from a higher value, which would mess up the number of pulses you get.

[AlexKeisy]

Thank You! But no Effect.

Thank You!!! It`s need to reset slave timer parameters.

TIM2->EGR |= TIM_EGR_UG;

[AlexKeisy]

Interface is very close to SPI, but data maybe 6-19 bit per pixel.

[AlexKeisy]

//RESULT CODE. Thanks for ALL!
 
  TIM2->CR1 |= TIM_CR1_ARPE;
  TIM2->PSC=0;
  TIM2->ARR=3-1;//3 tact`s per pulse
  TIM2->CCR2= 1;//pulse width 2 of 3
  TIM2->CCER |= (TIM_CCER_CC2E);
  TIM2->CCMR1 &=~( TIM_CCMR1_OC2M_0);
  TIM2->CCMR1 |= ( TIM_CCMR1_OC2M_1 |  TIM_CCMR1_OC2M_2);
 
  TIM2->SMCR &= ~(TIM_SMCR_SMS_Msk | TIM_SMCR_TS_Msk);
  //TIM2 slave gate mode and source ITR3
  TIM2->SMCR |= TIM_SMCR_SMS_0 | TIM_SMCR_SMS_2 | TIM_SMCR_TS_0 | TIM_SMCR_TS_1;
 
   // TIM4 up counting mode, pulse width to TRGO
   // Prescaler = 3_tact`s_per_pulse * 16_bits_per_Word -1
  TIM4->CNT = 0;
  TIM4->PSC = 3*16 -1;
  TIM4->ARR = len;
  TIM4->CR1 &= ~(TIM_CR1_ARPE_Msk | TIM_CR1_CKD_Msk | TIM_CR1_CMS_Msk |  TIM_CR1_DIR_Msk);
  TIM4->CR1 |= TIM_CR1_OPM ;
  TIM4->CR2 &= ~(TIM_CR2_CCDS_Msk |  TIM_CR2_MMS_Msk | TIM_CR2_TI1S_Msk);
  //CNT_EN  of TIM4 is used as TRGO
  TIM4->CR2 |= TIM_CR2_MMS_0;
 
  //reset counters
  TIM4->EGR |= TIM_EGR_UG;
  TIM4->SR &= ~ TIM_SR_UIF_Msk;
  TIM2->EGR |= TIM_EGR_UG;
  TIM2->SR &= ~ TIM_SR_UIF_Msk;
  
  TIM2->CR1 |= TIM_CR1_CEN;
  TIM4->CR1 |= TIM_CR1_CEN;
   while (TIM4->CR1 & TIM_CR1_CEN){ cntr++; }