startup.c

/* include headers */

#include "stm32f4xx.h"

#include "work.h"

#include "xprintf.h"

/* external vars */

extern unsigned long _estack;

extern unsigned long __text_end;

extern unsigned long __data_start;

extern unsigned long __data_end;

extern unsigned long __bss_start;

extern unsigned long __bss_end;

void reset_handler(void) {

    unsigned long *src;

    unsigned long *dest;

    src = &__text_end;

    dest = &__data_start;

    if (src != dest)

        while(dest < &__data_end)

            *(dest++) = *(src++);

    dest = &__bss_start;

    while(dest < &__bss_end)

        *(dest++) = 0;

    /* call working code */

    work();

}

/* timer4 irq handler */

void tim4_irq_hanlder(void) {

    static unsigned int counter;

    counter++;

    if (TIM4->SR & TIM_SR_UIF) {

        /* switch leds */

        LED_PORT->ODR ^= RED_LED;

        /* send test string */

        xprintf("counter: %d : %x : %b\n", counter, counter, counter);

        /* clear status bit */

        TIM4->SR &= ~TIM_SR_UIF;

    }

}