// Define the PWM pin (PA8 is connected to TIM1_CH1)
#define PWM_PIN PA8

void setup() {
  // Initialize GPIO for PA8
  pinMode(PWM_PIN, OUTPUT);

  // Configure Timer1 for PWM on PA8
  RCC->APB2ENR |= RCC_APB2ENR_TIM1EN;   // Enable Timer1 clock
  RCC->APB2ENR |= RCC_APB2ENR_IOPAEN;  // Enable GPIOA clock
  
  GPIOA->CRH &= ~GPIO_CRH_CNF8;        // Clear CNF8 (PA8)
  GPIOA->CRH |= GPIO_CRH_CNF8_1;       // Set CNF8 as Alternate function push-pull
  GPIOA->CRH |= GPIO_CRH_MODE8_1;      // Set MODE8 as Output 2MHz
  
  TIM1->CCMR1 |= TIM_CCMR1_OC1M_1 | TIM_CCMR1_OC1M_2; // PWM mode 1
  TIM1->CCMR1 |= TIM_CCMR1_OC1PE;      // Enable preload for TIM1 Channel 1
  TIM1->CCER |= TIM_CCER_CC1E;         // Enable TIM1 Channel 1 output
  TIM1->ARR = 1000;                    // Set auto-reload value (PWM period)
  TIM1->PSC = 72 - 1;                  // Set prescaler (1 MHz timer clock)
  TIM1->CCR1 = 0;                      // Start with 0 duty cycle
  TIM1->BDTR |= TIM_BDTR_MOE;          // Enable Main Output
  TIM1->CR1 |= TIM_CR1_CEN;            // Start Timer1
}

void loop() {
  // Gradually increase brightness
  for (int duty = 0; duty <= 1000; duty += 10) {
    TIM1->CCR1 = duty;  // Set duty cycle
    delay(10);          // Delay to see brightness change
  }
  
  // Gradually decrease brightness
  for (int duty = 1000; duty >= 0; duty -= 10) {
    TIM1->CCR1 = duty;  // Set duty cycle
    delay(10);          // Delay to see brightness change
  }
}