/*
 * This program toggles the four LEDs of the EduBase board.
 *
 * The four LEDs are:
 * LED3 - PB7
 * LED2 - PB6
 * LED1 - PB5
 * LED0 - PB4
 */

#include "stm32f4xx.h"

void delayMs(int n);

int main(void) {
    RCC->AHB1ENR |=  2;             /* enable GPIOB clock */
    GPIOB->MODER &= ~0x0000ff00;    /* clear pin mode */
    GPIOB->MODER |=  0x00005500;    /* set pins to output mode */

    while (1) {
        GPIOB->ODR |=  0x00000050;  /* turn on  LED 2, 0 */
        GPIOB->ODR &= ~0x000000A0;  /* turn off LED 3, 1 */
        delayMs(500);
        GPIOB->ODR &= ~0x00000050;  /* turn off LED 2, 0 */
        GPIOB->ODR |=  0x000000A0;  /* turn on  LED 3, 1 */
        delayMs(500);
    }
}

/* 16 MHz SYSCLK */
void delayMs(int n) {
    int i;
    for (; n > 0; n--)
        for (i = 0; i < 3195; i++) ;
}