fastest way to generate output waveform

Posted on May 17, 2011 at 13:48

''''I''ll put some code for fast PWM''

But he didn't want PWM;  just a fixed-period, fixed duty cycle - and not very fast at that!

Posted on May 17, 2011 at 13:48

 Do some efforts its not that hard just take help from STM32 library code

If still not get sucess ''ll put some code fot fast PWM with period 50 usec(yes usec not msec...) and with variable duty cycle output.

Posted on May 17, 2011 at 13:48

PWM, in this context, is 

P

ulse

W

idth

M

odulation

http://en.wikipedia.org/wiki/Pulse-width_modulation

Posted on May 17, 2011 at 13:48

I got it working using TIMx as Toggle, here is my init and interrupt routine. I choosed a prescaler value and parametrized CC1 register to have different freq/duty cycle. In the service routine I select the counter toggle value in order to have the right duty cycle. Is that the better way to do this?

Would you explain to me what is the PWM? I'm just learning and I really get lost. Thanks and best regards.

Filippo

void Waveform_On(void)

{

  NVIC_InitTypeDef NVIC_InitStructure;

  GPIO_InitTypeDef GPIO_InitStructure;

 

  /* TIM3 clock enable */

  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

  /* GPIOA clock enable */

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB|

                         RCC_APB2Periph_GPIOC | RCC_APB2Periph_AFIO, ENABLE);

 

    /* Enable the TIM3 global Interrupt */

  NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;

  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

  NVIC_Init(&NVIC_InitStructure);

  

    // timer out

  GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_6;

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;

  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

  GPIO_Init(GPIOC, &GPIO_InitStructure);

  GPIO_PinRemapConfig(GPIO_FullRemap_TIM3, ENABLE); 

 

// timer init

  /* Time base configuration */

  TIM_TimeBaseStructure.TIM_Period = 65535;

  TIM_TimeBaseStructure.TIM_Prescaler = TIM3_PRESCALER;

  TIM_TimeBaseStructure.TIM_ClockDivision = 0;

  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

  TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

  /* Output Compare Toggle Mode configuration: Channel1 */

  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle;

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

  TIM_OCInitStructure.TIM_Pulse = TIM3_CCR1_ON;

  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;

  TIM_OC1Init(TIM3, &TIM_OCInitStructure);

  TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Disable);

  /* TIM enable counter */

  TIM_Cmd(TIM3, ENABLE);

  /* TIM IT enable */

  TIM_ITConfig(TIM3, TIM_IT_CC1, ENABLE); 

 }

#define TV0ON 5 // ms

#define TV0_DUTYCYCLE 10 // in %

#if defined(CORE_CLOCK_36MHZ)

  #define TIM3_PRESCALER 72

  #define TIM3_CCR1_ON (36000000 / 2000 / TIM3_PRESCALER * TV0ON)

  #define TIM3_CCR1_OFF (TIM3_CCR1_ON * ((100-TV0_DUTYCYCLE)/TV0_DUTYCYCLE))

#elif defined(CORE_CLOCK_8MHZ)

  #define TIM3_PRESCALER 16

  #define TIM3_CCR1_ON  (8000000 / 2000 / TIM3_PRESCALER * TV0ON)

  #define TIM3_CCR1_OFF (TIM3_CCR1_ON * ((100-TV0_DUTYCYCLE)/TV0_DUTYCYCLE))

#endif

void TIM3_IRQHandler(void)

{

  if (TIM_GetITStatus(TIM3, TIM_IT_CC1) != RESET)

  {

    TIM_ClearITPendingBit(TIM3, TIM_IT_CC1 );

    capture = TIM_GetCapture1(TIM3);

    if (V0STATUS)

    {

      V0STATUS = 0;

      TIM_SetCompare1(TIM3, capture + TIM3_CCR1_ON );

    }

    else

    {

      V0STATUS = 1;

      TIM_SetCompare1(TIM3, capture + TIM3_CCR1_OFF );

    }

   

  }

}