STM32F4 PWM

void TIM_Config(void)

{

  GPIO_InitTypeDef GPIO_InitStructure;

  /* TIM3 clock enable */

  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

  /* GPIOC and GPIOB clock enable */

  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC | RCC_AHB1Periph_GPIOB, ENABLE);

   

  /* GPIOC Configuration: TIM3 CH1 (PC6) and TIM3 CH2 (PC7) */

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7 ;

  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(GPIOC, &GPIO_InitStructure);

   

  /* GPIOB Configuration:  TIM3 CH3 (PB0) and TIM3 CH4 (PB1) */

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1;

  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(GPIOB, &GPIO_InitStructure);

  /* Connect TIM3 pins to AF2 */ 

  GPIO_PinAFConfig(GPIOC, GPIO_PinSource6, GPIO_AF_TIM3);

  GPIO_PinAFConfig(GPIOC, GPIO_PinSource7, GPIO_AF_TIM3);

  GPIO_PinAFConfig(GPIOB, GPIO_PinSource0, GPIO_AF_TIM3);

  GPIO_PinAFConfig(GPIOB, GPIO_PinSource1, GPIO_AF_TIM3);

}




void PWM_Config(int period)

{

  uint16_t PrescalerValue = 0;

  /* Compute the prescaler value */

  PrescalerValue = (uint16_t) ((SystemCoreClock /2) / 28000000) - 1;

  /* Time base configuration */

  TIM_TimeBaseStructure.TIM_Period = period;

  TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue;

  TIM_TimeBaseStructure.TIM_ClockDivision = 0;

  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

  TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

  /* PWM1 Mode configuration: Channel1 */

  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

  TIM_OCInitStructure.TIM_Pulse = 0;

  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

  TIM_OC1Init(TIM3, &TIM_OCInitStructure);

  TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable);

  /* PWM1 Mode configuration: Channel2 */

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

  TIM_OCInitStructure.TIM_Pulse = 0;

  TIM_OC2Init(TIM3, &TIM_OCInitStructure);

  TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);

  /* PWM1 Mode configuration: Channel3 */

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

  TIM_OCInitStructure.TIM_Pulse = 0;

  TIM_OC3Init(TIM3, &TIM_OCInitStructure);

  TIM_OC3PreloadConfig(TIM3, TIM_OCPreload_Enable);

  /* PWM1 Mode configuration: Channel4 */

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

  TIM_OCInitStructure.TIM_Pulse = 0;

  TIM_OC4Init(TIM3, &TIM_OCInitStructure);

  TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Enable);

  TIM_ARRPreloadConfig(TIM3, ENABLE);

  /* TIM3 enable counter */

  TIM_Cmd(TIM3, ENABLE);

}




void PWM_SetDC(uint16_t channel,uint16_t dutycycle)

{

  if (channel == 1)

  {

    TIM3->CCR1 = dutycycle;

  }

  else if (channel == 2)

  {

    TIM3->CCR2 = dutycycle;

  }

  else if (channel == 3)

  {

    TIM3->CCR3 = dutycycle;

  }

  else

  {

    TIM3->CCR4 = dutycycle;

  }

}




The dutycycle is given as .

/* Includes ------------------------------------------------------------------*/
#include "stm32f4_discovery.h"
#include <stdio.h>

/* Private typedef -----------------------------------------------------------*/
GPIO_InitTypeDef  GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_OCInitTypeDef  TIM_OCInitStructure;
/* Private define ------------------------------------------------------------*/
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
/* Private function prototypes -----------------------------------------------*/
void TIM_Config(void);
void PWM_Config(int period);
void PWM_SetDC(uint16_t channel,uint16_t dutycycle);
void Delay(__IO uint32_t nCount);
void LED_Config(void);
/* Private functions ---------------------------------------------------------*/

/**
  * @brief  Main program
  * @param  None
  * @retval None
  */
int main(void)
{
  uint16_t pulse_width = 0;
  /* TIM Configuration */
  TIM_Config();
  /* LED Configuration */
  LED_Config();
  /* PWM Configuration */
  PWM_Config(800);

  PWM_SetDC(1,100);
  PWM_SetDC(2,100);
  PWM_SetDC(3,100);
  PWM_SetDC(4,100);
  while (1)
  {
    /* PD12 to be toggled */
    GPIO_ToggleBits(GPIOD, GPIO_Pin_13);
    PWM_SetDC(1,pulse_width++);
    if (pulse_width > 800)
    {
      pulse_width = 0;
    }
    Delay(100000);
  }
}

/**
  * @brief  Configure the TIM3 Ouput Channels.
  * @param  None
  * @retval None
  */
void TIM_Config(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;

  /* TIM3 clock enable */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

  /* GPIOC and GPIOB clock enable */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC | RCC_AHB1Periph_GPIOB, ENABLE);
  
  /* GPIOC Configuration: TIM3 CH1 (PC6) and TIM3 CH2 (PC7) */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7 ;
  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(GPIOC, &GPIO_InitStructure); 
  
  /* GPIOB Configuration:  TIM3 CH3 (PB0) and TIM3 CH4 (PB1) */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1;
  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(GPIOB, &GPIO_InitStructure); 

  /* Connect TIM3 pins to AF2 */  
  GPIO_PinAFConfig(GPIOC, GPIO_PinSource6, GPIO_AF_TIM3);
  GPIO_PinAFConfig(GPIOC, GPIO_PinSource7, GPIO_AF_TIM3); 
  GPIO_PinAFConfig(GPIOB, GPIO_PinSource0, GPIO_AF_TIM3);
  GPIO_PinAFConfig(GPIOB, GPIO_PinSource1, GPIO_AF_TIM3); 
}

void PWM_Config(int period)
{
  uint16_t PrescalerValue = 0;
  /* -----------------------------------------------------------------------
    TIM3 Configuration: generate 4 PWM signals with 4 different duty cycles.
    
    In this example TIM3 input clock (TIM3CLK) is set to 2 * APB1 clock (PCLK1), 
    since APB1 prescaler is different from 1.   
      TIM3CLK = 2 * PCLK1  
      PCLK1 = HCLK / 4 
      => TIM3CLK = HCLK / 2 = SystemCoreClock /2
          
    To get TIM3 counter clock at 28 MHz, the prescaler is computed as follows:
       Prescaler = (TIM3CLK / TIM3 counter clock) - 1
       Prescaler = ((SystemCoreClock /2) /28 MHz) - 1
                                              
    To get TIM3 output clock at 30 KHz, the period (ARR)) is computed as follows:
       ARR = (TIM3 counter clock / TIM3 output clock) - 1
           = 665

    Note: 
     SystemCoreClock variable holds HCLK frequency and is defined in system_stm32f4xx.c file.
     Each time the core clock (HCLK) changes, user had to call SystemCoreClockUpdate()
     function to update SystemCoreClock variable value. Otherwise, any configuration
     based on this variable will be incorrect.    
  ----------------------------------------------------------------------- */  

  /* Compute the prescaler value */
  PrescalerValue = (uint16_t) ((SystemCoreClock /2) / 28000000) - 1;

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

  TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

  /* PWM1 Mode configuration: Channel1 */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 0;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

  TIM_OC1Init(TIM3, &TIM_OCInitStructure);

  TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable);

  /* PWM1 Mode configuration: Channel2 */
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 0;

  TIM_OC2Init(TIM3, &TIM_OCInitStructure);

  TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);

  /* PWM1 Mode configuration: Channel3 */
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 0;

  TIM_OC3Init(TIM3, &TIM_OCInitStructure);

  TIM_OC3PreloadConfig(TIM3, TIM_OCPreload_Enable);

  /* PWM1 Mode configuration: Channel4 */
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 0;

  TIM_OC4Init(TIM3, &TIM_OCInitStructure);

  TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Enable);

  TIM_ARRPreloadConfig(TIM3, ENABLE);

  /* TIM3 enable counter */
  TIM_Cmd(TIM3, ENABLE);
}

void PWM_SetDC(uint16_t channel,uint16_t dutycycle)
{
  if (channel == 1)
  {
    TIM3->CCR1 = dutycycle;
  }
  else if (channel == 2)
  {
    TIM3->CCR2 = dutycycle;
  }
  else if (channel == 3)
  {
    TIM3->CCR3 = dutycycle;
  }
  else 
  {
    TIM3->CCR4 = dutycycle;
  }
}

void LED_Config(void)
{
  /* GPIOD Periph clock enable */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);

  /* Configure PD12, PD13, PD14 and PD15 in output pushpull mode */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12 | GPIO_Pin_13| GPIO_Pin_14| GPIO_Pin_15;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_Init(GPIOD, &GPIO_InitStructure);

}





/**
  * @brief  Delay Function.
  * @param  nCount:specifies the Delay time length.
  * @retval None
  */
void Delay(__IO uint32_t nCount)
{
  while(nCount--)
  {
  }
}