#include "stm32c0xx.h"

int main(void)
{
    /* enable GPIOB clock */

    RCC->IOPENR |= (1 << 1);   // GPIOB clock enable

    /* set PB7 as output */

    GPIOB->MODER &= ~(3 << (7 * 2));
    GPIOB->MODER |=  (1 << (7 * 2));

    while (1)
    {
        /* set PB7 */

        GPIOB->ODR |= (1 << 7);

        for(volatile uint32_t i = 0; i < 500000; i++);

        /* reset PB7 */

        GPIOB->ODR &= ~(1 << 7);

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