void startup(void) __attribute__((naked)) __attribute__((section (".start_section")) );

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 */
    ) ;
}

#define EXTI_BASE (0x40013C00)
#define EXTI_IMR ((volatile uint32_t *) (EXTI_BASE))
#define EXTI_RTSR ((volatile uint32_t *) (EXTI_BASE + 8))
#define EXTI_FTSR ((volatile uint32_t *) (EXTI_BASE + 0xC))
#define EXTI_PR ((volatile uint32_t *) (EXTI_BASE + 0x14))

#define NVIC_ISER0 ((unsigned int *) 0xE000E100)

#define SCB_VTOR ((volatile unsigned int *) (0xE000ED08))
#define SYSCFG_EXTICR1 0x40013808

void app_init (void);
void irq_init (void);
unsigned char keyb(void);
void out7seg(unsigned char c);
void systick_irq_handler(void);
int measure_distance(void);
void exti_1_handler(void);
void systick_calls(void);

static volatile int unit            = 58*10;        // 58*centimeters
static volatile int measure_delay   = 100;          // denotes how long delay in ms between distance measurement
static volatile char irq_1_flag;
static volatile char systick_flag;
static volatile int delay_counter;

static volatile char measuring;
static volatile int measuring_counter;
static volatile int measuring_result;

#include "stm32f4xx.h"
#include "stm32f4xx_rcc.h"
#include "stm32f4xx_gpio.h"

void main(void){
    app_init();
	irq_1_flag = 0;
	char segmap[16] = {0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x3D,0x07,0x7F,0x67,0x77,0x7C,0x39,0x5F,0x79,0x71};
	//out7seg(segmap[1] + 0x80);
	irq_init();
	//out7seg(segmap[2] + 0x80);
    unsigned int distance;
	//out7seg(segmap[3] + 0x80);
	measure_distance();
	delay_1mikro();
    while(1){
		//out7seg(segmap[4] + 0x80);
        //distance = measure_distance();
		if(measuring == 0){
			if (measuring_result > 15){
				measuring_result = 15;
			}
			out7seg(segmap[measuring_result]);

			delay_x_ms(measure_delay);
			measure_distance();
		}
		//out7seg(segmap[5] + 0x80);
    }


}

//int measure_distance(void){
void measure_distance(void){
    //int counter = 0;
    //int distance = 0;
	//char segmap[16] = {0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x67,0x77,0x7C,0x39,0x5F,0x79,0x71};
	GPIO_ResetBits(GPIOE,GPIO_Pin_0);
    delay_10mikro();
	GPIO_SetBits(GPIOE,GPIO_Pin_0);
    delay_10mikro();
	GPIO_ResetBits(GPIOE,GPIO_Pin_0);
	measuring = 1;
	measuring_counter = 0;

	/*
    //while(~GPIO_ReadInputData(GPIOE) & 2){
    //}
    //while(GPIO_ReadInputData(GPIOE) & 2){
    while(irq_1_flag == 0){
        delay_1mikro();
        counter++;
		//out7seg(segmap[irq_1_flag] + 0x80);
    }
	//out7seg(segmap[2] + 0x80);
	irq_1_flag = 0;
    distance = counter/unit;

    return distance;
	*/
}

void exti_1_handler(void){
	//out7seg(0x67 + 0x80);
	if(*EXTI_PR & 2){
		irq_1_flag = 1;
		*EXTI_PR |= 2;
		measuring = 0;
		measuring_result = measuring_counter / unit;
	}
}

void delay_1mikro(void){
	SysTick->CTRL = 0;
    SysTick->LOAD = (168-1);
    SysTick->VAL = 0;
	//SysTick->CTRL = 5;
    SysTick->CTRL = 7;

    // COUNTFLAG is a bit that is set to 1 when counter reaches 0.
    // It's automatically cleared when read.
    //while ((SysTick->CTRL & 0x10000) == 0);

	/*
	while(systick_flag == 0){}
	systick_flag = 0;
    SysTick->CTRL = 0;
	*/
}

void delay_10mikro(void){
    for(int i = 0; i < 10; i++){
    delay_1mikro();
    }
}

void delay_x_ms(int x){
	delay_counter = 0;
	while(delay_counter < (x*1000)){

	}
	/*
    for(int i = 0; i < (x*1000); i++){
        delay_1mikro();
    }
	*/
}

void systick_calls(void){
	delay_counter++;
	if(measuring == 1){
		measuring_counter ++;
	}
}

void app_init(void) {

	RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);

	GPIO_InitTypeDef GPIOD_Out_InitDef;

    GPIOD_Out_InitDef.GPIO_Pin = GPIO_Pin_All;
    GPIOD_Out_InitDef.GPIO_Mode = GPIO_Mode_OUT;
    GPIOD_Out_InitDef.GPIO_OType = GPIO_OType_PP;
    GPIOD_Out_InitDef.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIOD_Out_InitDef.GPIO_Speed = GPIO_Speed_100MHz;
    //Initialize pins
    GPIO_Init(GPIOD, &GPIOD_Out_InitDef);

	RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE);
	GPIO_InitTypeDef GPIOE_Out_InitDef;

    GPIOE_Out_InitDef.GPIO_Pin = GPIO_Pin_0;
    GPIOE_Out_InitDef.GPIO_Mode = GPIO_Mode_OUT;
    GPIOE_Out_InitDef.GPIO_OType = GPIO_OType_PP;
    GPIOE_Out_InitDef.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIOE_Out_InitDef.GPIO_Speed = GPIO_Speed_100MHz;
    //Initialize pins
    GPIO_Init(GPIOE, &GPIOE_Out_InitDef);

	GPIO_InitTypeDef GPIOE_In_InitDef;

    GPIOE_In_InitDef.GPIO_Pin = GPIO_Pin_1;
    GPIOE_In_InitDef.GPIO_Mode = GPIO_Mode_IN;
    GPIOE_In_InitDef.GPIO_OType = GPIO_OType_PP;
    GPIOE_In_InitDef.GPIO_PuPd = GPIO_PuPd_UP;
    GPIOE_In_InitDef.GPIO_Speed = GPIO_Speed_100MHz;
    //Initialize pins
    GPIO_Init(GPIOE, &GPIOE_In_InitDef);

}

void systick_irq_handler(void){
	SysTick->CTRL = 0;
	//systick_flag = 1;
	delay_1mikro();
	systick_calls();
}

void irq_init(void){

	*((unsigned long *) 0x40023830) = 0x18;
	*((unsigned long *) 0x40023844) = 0x4000;
    *SCB_VTOR = 0x2001C000;
    *((void (**)(void) ) (*SCB_VTOR + 0x3C)) = systick_irq_handler;
    //*((void (**)(void) ) (*SCB_VTOR + 0x64)) = exti_3_handler;
    //*((void (**)(void) ) (*SCB_VTOR + 0x60)) = exti_2_handler;
    *((void (**)(void) ) (*SCB_VTOR + 0x5C)) = exti_1_handler;
    //*((void (**)(void) ) (*SCB_VTOR + 0x58)) = exti_0_handler;


    *((unsigned int *) SYSCFG_EXTICR1) &= ~0x00F0;
    *((unsigned int *) SYSCFG_EXTICR1) |= 0x0040;

    *EXTI_IMR |= 2;
    *EXTI_FTSR |= 2;
    *EXTI_RTSR &= ~2;

    *((unsigned int *) 0xE000E100) |= (0x80);
}

void out7seg(unsigned char c) {
	GPIO_ResetBits(GPIOD, GPIO_Pin_All);
    GPIO_SetBits(GPIOD, c);
	//char segmap[16] = {0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x3D,0x07,0x7F,0x67,0x77,0x7C,0x39,0x5F,0x79,0x71};
	//GPIOD_ODR_LOW = c;
}