/* Includes ------------------------------------------------------------------*/
#include "main.h"

/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_OCInitTypeDef  TIM_OCInitStructure;

__IO uint16_t uhCCR1_Val = 40961;
__IO uint16_t uhCCR2_Val = 20480;
__IO uint16_t uhCCR3_Val = 10240;
__IO uint16_t uhCCR4_Val = 5120;

uint16_t uhPrescalerValue = 0;

/* Private function prototypes -----------------------------------------------*/
static void TIM_Config(void);

/* Private functions ---------------------------------------------------------*/

/**
  * @brief  Main program
  * @param  None
  * @retval None
  */
int main(void)
{
  /*!< At this stage the microcontroller clock setting is already configured,
       this is done through SystemInit() function which is called from startup
       files (startup_stm32f40_41xxx.s/startup_stm32f427_437xx.s/startup_stm32f429_439xx.s)
       before to branch to application main.
       To reconfigure the default setting of SystemInit() function, refer to
       system_stm32f4xx.c file
     */

  /* TIM Configuration */
  TIM_Config();

  /* ---------------------------------------------------------------------------
    TIM3 Configuration: Output Compare Toggle Mode:

    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 21 MHz, the prescaler is computed as follows:
       Prescaler = (TIM3CLK / TIM3 counter clock) - 1
       Prescaler = ((SystemCoreClock /2) /21 MHz) - 1

     CC1 update rate = TIM3 counter clock / uhCCR1_Val = 512.68 Hz
       ==> So the TIM3 Channel 1 generates a periodic signal with a
           frequency equal to 256.35 Hz.

     CC2 update rate = TIM3 counter clock / uhCCR2_Val = 1025.39 Hz
       ==> So the TIM3 Channel 2 generates a periodic signal with a
           frequency equal to 512.7 Hz.

     CC3 update rate = TIM3 counter clock / uhCCR3_Val = 2050.8 Hz
       ==> So the TIM3 Channel 3 generates a periodic signal with a
           frequency equal to 1025.4 Hz.

     CC4 update rate = TIM3 counter clock / uhCCR4_Val = 4101.56 Hz
       ==> So the TIM3 Channel 4 generates a periodic signal with a
           frequency equal to 2050.78 Hz.

    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 */
  uhPrescalerValue = (uint16_t) ((SystemCoreClock / 2) / 21000000) - 1;

  /* Time base configuration */
  TIM_TimeBaseStructure.TIM_Period = 65535;
  TIM_TimeBaseStructure.TIM_Prescaler = uhPrescalerValue;
  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 = uhCCR1_Val;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
  TIM_OC1Init(TIM3, &TIM_OCInitStructure);

  TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Disable);

  /* Output Compare Toggle Mode configuration: Channel2 */
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = uhCCR2_Val;

  TIM_OC2Init(TIM3, &TIM_OCInitStructure);

  TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Disable);

  /* Output Compare Toggle Mode configuration: Channel3 */
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = uhCCR3_Val;

  TIM_OC3Init(TIM3, &TIM_OCInitStructure);

  TIM_OC3PreloadConfig(TIM3, TIM_OCPreload_Disable);

  /* Output Compare Toggle Mode configuration: Channel4 */
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = uhCCR4_Val;

  TIM_OC4Init(TIM3, &TIM_OCInitStructure);

  TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Disable);

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

  /* TIM IT enable */
  TIM_ITConfig(TIM3, TIM_IT_CC1 | TIM_IT_CC2 | TIM_IT_CC3 | TIM_IT_CC4, ENABLE);

  while (1)
  {
  }
}

/**
  * @brief  Configure the TIM3 Pins.
  * @param  None
  * @retval None
  */
static void TIM_Config(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;
  NVIC_InitTypeDef NVIC_InitStructure;

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

  /* GPIOC clock enable */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);

  /* GPIOC Configuration: TIM3 CH1 (PC6), TIM3 CH2 (PC7), TIM3 CH2 (PC8) and TIM3 CH4 (PC9) */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7 | GPIO_Pin_8 | GPIO_Pin_9;
  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);

  /* Connect TIM Channels to AF2 */
  GPIO_PinAFConfig(GPIOC, GPIO_PinSource6, GPIO_AF_TIM3);
  GPIO_PinAFConfig(GPIOC, GPIO_PinSource7, GPIO_AF_TIM3);
  GPIO_PinAFConfig(GPIOC, GPIO_PinSource8, GPIO_AF_TIM3);
  GPIO_PinAFConfig(GPIOC, GPIO_PinSource9, GPIO_AF_TIM3);

  /* 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);
}