/* p2_4.c Display number 75 on a 2-digit 7-segment common cathode LED.
 *
 * The segments are driven by Port C0-C6.
 * The digit selects are driven by PB0 and PB1.
 *
 * This program was tested with Keil uVision v5.23 with DFP v2.0.0
 */

#include "stm32f0xx.h"

void delayMs(int n);
int main(void) {
    RCC->AHBENR |= 0x00040000;      /* enable GPIOB clock */
    RCC->AHBENR |= 0x00080000;      /* enable GPIOC clock */

    GPIOC->MODER &= ~0x0000FFFF;    /* clear pin mode */
    GPIOC->MODER |=  0x00005555;    /* set pins to output mode */
    GPIOB->MODER &= ~0x0000000F;    /* clear pin mode */
    GPIOB->MODER |=  0x00000005;    /* set pins to output mode */

    for(;;)
    {
        GPIOB->BRR = 0x00000001;    /* deselect ones digit */
        GPIOC->ODR = 0x0007;        /* display tens digit */
        GPIOB->BSRR = 0x00000002;   /* select tens digit */
        delayMs(8);
        GPIOB->BRR = 0x00000002;    /* deselect tens digit */
        GPIOC->ODR = 0x006D;        /* display ones digit */
        GPIOB->BSRR = 0x00000001;   /* select ones digit */
        delayMs(8);
    }
}

/* 8 MHz SYSCLK */
void delayMs(int n) {
    int i;
    for (; n > 0; n--)
        for (i = 0; i < 1142; i++) ;
}