#include "stm32f1xx_hal.h"

TIM_HandleTypeDef htim3;

static void Gpio_Init(void);
static void Tim3_Init(void);
static void setPWM(TIM_HandleTypeDef, uint32_t, uint16_t, uint16_t);

int main(void)
{
    /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
    HAL_Init();
    /* Initialize all configured peripherals */
    Gpio_Init();
    Tim3_Init();

    HAL_TIM_PWM_Start(&htim3, TIM_CHANNEL_1);

    /* Infinite loop */
    while (1)
    {
      for(int i=0; i<256; i++){
      setPWM(htim3, TIM_CHANNEL_1, 255, i);
      HAL_Delay(1);
      } 
    }
}

/* Systick handler */
void SysTick_Handler(void)
{
    HAL_IncTick();
}

void Gpio_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct ={0};
  __HAL_RCC_GPIOA_CLK_ENABLE();
  GPIO_InitStruct.Pin = GPIO_PIN_6;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_LOW;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
}

/* Timer init function */
void Tim3_Init(void)
{
  __HAL_RCC_TIM3_CLK_ENABLE();
  
  TIM_ClockConfigTypeDef sClockSourceConfig = {0};
  TIM_MasterConfigTypeDef sMasterConfig = {0};
  TIM_OC_InitTypeDef sConfigOC = {0};

  htim3.Instance = TIM3;
  htim3.Init.Prescaler = 8-1;
  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim3.Init.Period = 4095;
  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_ENABLE;
  HAL_TIM_Base_Init(&htim3);

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig);
  HAL_TIM_PWM_Init(&htim3);

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig);

  sConfigOC.OCMode = TIM_OCMODE_PWM1;
  sConfigOC.Pulse = 0;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_1);
  }

void setPWM(TIM_HandleTypeDef timer, uint32_t channel, uint16_t period, uint16_t pulse)
{
 HAL_TIM_PWM_Stop(&timer, channel); // stop generation of pwm
 TIM_OC_InitTypeDef sConfigOC;
 timer.Init.Period = period; // set the period duration
 HAL_TIM_PWM_Init(&timer); // reinititialise with new period value
 sConfigOC.OCMode = TIM_OCMODE_PWM1;
 sConfigOC.Pulse = pulse; // set the pulse duration
 sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
 sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
 HAL_TIM_PWM_ConfigChannel(&timer, &sConfigOC, channel);
 HAL_TIM_PWM_Start(&timer, channel); // start pwm generation
}