#include "stm32c0xx.h"  // Include STM32C0 specific header file

volatile uint8_t led_state = 0;  // Variable to keep track of the LED state

// Function to initialize LEDs (PA0 to PA3) as output
void LED_Init(void) {
    // Enable GPIOA clock (RCC_IOPENR: I/O port A enable)
    RCC->IOPENR |= RCC_IOPENR_GPIOAEN;

    // Configure PA0 to PA3 as output (00 for input, 01 for output)
    GPIOA->MODER &= ~(0xFF);  // Clear bits for PA0-PA3
    GPIOA->MODER |= 0x55;     // Set PA0 to PA3 as outputs (01)
}

// Function to initialize buttons (PA4 and PA5) as inputs with external interrupts
void Button_Init(void) {
    // Enable SYSCFG clock to configure external interrupts
    RCC->APBENR2 |= RCC_APBENR2_SYSCFGEN;

    // Configure PA4 and PA5 as input (00 in MODER)
    GPIOA->MODER &= ~(0xF << (4 * 2));  // Clear mode for PA4 and PA5

    // Set PA4 and PA5 with pull-up resistors (to avoid floating)
    GPIOA->PUPDR &= ~(0xF << (4 * 2));  // Clear pull-up/down settings
    GPIOA->PUPDR |= (0x5 << (4 * 2));   // Set PA4 and PA5 to pull-up (01)

    // Configure external interrupt for PA4 and PA5 (EXTI lines 4 and 5)
    SYSCFG->EXTICR[1] |= (0 << SYSCFG_EXTICR2_EXTI4_Pos);  // Map PA4 to EXTI4
    SYSCFG->EXTICR[1] |= (0 << SYSCFG_EXTICR2_EXTI5_Pos);  // Map PA5 to EXTI5

    EXTI->IMR1 |= EXTI_IMR1_IM4 | EXTI_IMR1_IM5;      // Enable interrupt for PA4 and PA5
    EXTI->FTSR1 |= EXTI_FTSR1_FT4 | EXTI_FTSR1_FT5;   // Trigger on falling edge for PA4 and PA5

    // Enable EXTI interrupts in NVIC
    NVIC_EnableIRQ(EXTI4_15_IRQn);  // Enable EXTI lines 4-15 in NVIC
}

// Interrupt handler for EXTI lines 4 to 15 (PA4 and PA5)
void EXTI4_15_IRQHandler(void) {
    if (EXTI->RPR1 & EXTI_RPR1_RPIF4) {  // Check if PA4 (EXTI4) triggered
        led_state ^= 1;  // Toggle LED state
        if (led_state) {
            GPIOA->ODR |= 0x0F;  // Turn on LEDs (PA0-PA3)
        } else {
            GPIOA->ODR &= ~0x0F;  // Turn off LEDs (PA0-PA3)
        }
        EXTI->RPR1 |= EXTI_RPR1_RPIF4;  // Clear interrupt pending flag for PA4
    }

    if (EXTI->RPR1 & EXTI_RPR1_RPIF5) {  // Check if PA5 (EXTI5) triggered
        led_state ^= 1;  // Toggle LED state
        if (led_state) {
            GPIOA->ODR |= 0x0F;  // Turn on LEDs (PA0-PA3)
        } else {
            GPIOA->ODR &= ~0x0F;  // Turn off LEDs (PA0-PA3)
        }
        EXTI->RPR1 |= EXTI_RPR1_RPIF5;  // Clear interrupt pending flag for PA5
    }
}

void setup()(void) {
    LED_Init();    // Initialize the LEDs (PA0-PA3)
    Button_Init(); // Initialize buttons with interrupts (PA4, PA5)

    while (1) {
        // Main loop does nothing; all logic is handled in the interrupt handler
    }
}


void loop()
{}