#include "stm32c0xx.h"

void delay(void)
{
    for (volatile uint32_t i = 0; i < 500000; i++)
    {
    }
}

int main(void)
{
    // 1. Enable GPIOB clock
    RCC->IOPENR |= (1U << 1);
  
    // 2. Configure PB3 as output
    GPIOB->MODER &= ~(3U << 6);
    GPIOB->MODER |=  (1U << 6);

    //3. Configure PB5 as input
    GPIOB->MODER &=~(3U << 10);

    //4. PB5 internal ull up
    GPIOB->PUPDR &=~(3U<<10);
    GPIOB->PUPDR |=(1U<<10);

    while (1)
    {
        if (!(GPIOB->IDR & (1U << 5)))// check if pin 5 is high
        {
            GPIOB->BSRR = (1U << 3); //LED ON
  
        }
        else // 4. LED OFF
        {
            GPIOB->BSRR = (1U << 19);
          
        }
    }
}