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STM32F4-discovery DDS

Question asked by Baev.Alexander on Apr 7, 2015
Latest reply on Apr 8, 2015 by Baev.Alexander
Hi.
I try to make DDS. The code is below. The idea is to get new value of capture-compare register after Update event. This is done in the update interrupt. I have the following problems: 1) I do not see zero in the train of pulses, while it is present in the array; 2) I see some pulses which should not be (I attached the images - in the lower one is shown the marked pule of the upper image, only one pulse has such artifacts others pulses are ok ).
How those problems can be solved?
Maybe I should use one pulse mode?
Thanks!
/*
My file as replacement for main.c of TIM_PWMOutput project
This is DDS test
Original main.c is excluded from compiling
*/

#include "stm32f4xx.h"

TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_OCInitTypeDef  TIM_OCInitStructure;

/* Private variables ---------------------------------------------------------*/
uint16_t CCR1_Val = 350;
uint16_t PrescalerValue = 0;
int sinus[60]={349, 385, 422, 457, 491, 523, 554, 583, 608, 631, 651, 668,
681, 690, 696, 698, 696, 690, 681, 668, 651, 631, 608, 583, 554, 524, 491,
457, 422, 385, 349, 313, 276, 241, 207, 175, 144, 115, 90, 67, 47, 30, 17,
8, 2, 0, 2, 8, 17, 30, 47, 67, 90, 115, 144, 174, 207, 241, 276, 313};

void TIM_Config(void);
void TIM4_IRQHandler(void);

int main (void)
{
  /
  /* TIM Configuration */
  TIM_Config();
 
  /* -----------------------------------------------------------------------
    TIM4 Configuration: generate 4 PWM signals with 4 different duty cycles.
    
    In this example TIM4 input clock (TIM4CLK) is set to 4 * APB1 clock (PCLK1),
    since TIMPRE bit from RCC_DCKCFGR register is set.   
      TIM4CLK = 4 * PCLK1
      PCLK1 = HCLK / 4
      => TIM4CLK = HCLK = SystemCoreClock
          
    To get TIM4 counter clock at 21 MHz, the prescaler is computed as follows:
       Prescaler = (TIM4CLK / TIM4 counter clock) - 1
       Prescaler = (SystemCoreClock /21 MHz) - 1
                                              
    To get TIM4 output clock at 30 KHz, the period (ARR)) is computed as follows:
       ARR = (TIM4 counter clock / TIM4 output clock) - 1
           = 699
                  
   
  ----------------------------------------------------------------------- */   
  RCC_TIMCLKPresConfig(RCC_TIMPrescActivated);

  /* Compute the prescaler value */
  PrescalerValue = (uint16_t) (SystemCoreClock / 21000000) - 1;

  /* Time base configuration */
  TIM_TimeBaseStructure.TIM_Period = 699;
  TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

  TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);

  /* PWM1 Mode configuration: Channel1 */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = CCR1_Val;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

  TIM_OC1Init(TIM4, &TIM_OCInitStructure);

//  TIM_OC1PreloadConfig(TIM4, TIM_OCPreload_Enable);

//  TIM_ARRPreloadConfig(TIM4, ENABLE);
 
  TIM_ITConfig(TIM4, TIM_IT_Update, ENABLE);
 
  NVIC_InitTypeDef NVIC_InitStructure;
  NVIC_InitStructure.NVIC_IRQChannel = TIM4_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);

  /* TIM4 enable counter */
  TIM_Cmd(TIM4, ENABLE);

  while (1)
  {}
}

void TIM4_IRQHandler(void)
{
  static int i = 0;
  i++;
  if (i == 60) i = 0;
  TIM4->CCR1 = sinus[i];
  TIM_ClearFlag(TIM4, TIM_FLAG_Update);
}

void TIM_Config(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;

  /* TIM4 clock enable */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);

  /* GPIOD clock enable */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);
 
  /* GPIOD Configuration: TIM4 CH1 (PD12)*/
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP ;
  GPIO_Init(GPIOD, &GPIO_InitStructure);

  /* Connect TIM4 pins to AF2 */  
  GPIO_PinAFConfig(GPIOD, GPIO_PinSource12, GPIO_AF_TIM4);
 
}
train1.jpg

train2.jpg

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