/*
 *  startup.c
 *
 */
void startup(void) __attribute__((naked)) __attribute__((section (".start_section")) );

#ifdef SIMULATOR
#define DELAY_COUNT 100
#else
#define DELAY_COUNT 1000000
#endif
#define GPIO_D_MODER (volatile unsigned int *) 0X40020C00
#define GPIO_D_ODR_LOW (volatile unsigned int *) (0X40020C00 + 0x14)
#define SCB_VTOR (volatile unsigned int *) 0xE000ED08

#define STK_LOAD (volatile unsigned int *) (0xE000E014)
#define STK_CTRL (volatile unsigned int *) (0xE000E010)
#define STK_VAL (volatile unsigned int *) (0xE000E018)

static volatile int systick_flag;
static volatile int delay_count;

void startup ( void )
{
__asm volatile(
    " LDR R0,=0x2001C000\n"     /* set stack */
    " MOV SP,R0\n"
    " BL main\n"                /* call main */
    "_exit: B .\n"              /* never return */
    ) ;
}

void handler_X ( void )
{
    *GPIO_D_ODR_LOW = ~*GPIO_D_ODR_LOW;
}

void init_handler_X(void)
{
    * ( (void (**) (void) ) 0x2001C03C) = handler_X;
    systick_flag = 0;
}

void init_app (void)
{
    /* Initiera port D och undantagsvektor */
    *GPIO_D_MODER = 0x00005555;
    *SCB_VTOR = 0x2001C000;
    delay_count = DELAY_COUNT;

    init_handler_X();

}


void delay_1mikro(void)
{
    systick_flag = 0;
    *STK_CTRL = 0;
    *STK_LOAD = ( 168- 1);
    *STK_VAL = 0;
    *STK_CTRL = 7;

}

void delay (unsigned int count)
{
    if ( count == 0 )
    {
        return;
    }

    delay_count = count;
    systick_flag = 0;
    delay_1mikro();
}

void systick_irq_handler (void)
{
    *STK_CTRL = 0;
    delay_count--;
    if (delay_count > 0)
    {
        delay_1mikro();
    }
    else
    {
        systick_flag = 1;
    }
}

void main(void)
{
    init_app();
    *GPIO_D_ODR_LOW = 0;
    delay (DELAY_COUNT);
    *GPIO_D_ODR_LOW = 0xFF;
    while (1)
    {
        if (systick_flag)
            break;
    }

    *GPIO_D_ODR_LOW = 0;

}