//#include "suryaa.h"
#include <avr/interrupt.h>
static long distance=0;
void set_trigger_pin(void);//timer 3
void pin_configure(void);
void set_echo_pin(void);//timer4


void set_trigger_pin(void)
{
  volatile char*tccr3a,*tccr3b,*ocr3al,*ocr3ah,*tcnt3h,*tcnt3l;
  tccr3a=(volatile char*)0x90;
  tccr3b=(volatile char*)0x91;
  ocr3al=(volatile char*)0x98;
  ocr3ah=(volatile char*)0x99;
  tcnt3l=(volatile char*)0x94;
  tcnt3h=(volatile char*)0x95;

  *tcnt3l=0x00;
  *tcnt3h=0x00;
  *tccr3a = 0x40; // Set WGM02  bits for CTC mode and toggle OC0A on compare match
  *tccr3b = 0x4D; // Set CS00 and CS02 bits for (prescaler = 1024,for 1 tick 64 mic.s)
  *ocr3ah=0x01;//set compare match value(365)=365*64=23360m.s delay
  *ocr3al =0x6D;   // Set compare match value()
  Serial.println("trigger pin set successful");
}


void pin_configure(void)
{
  volatile char *dirL,*inL,*dire,*oute;
  dirL=(volatile char *)0x10A;//set portL first bit as input for echo pin.
  inL=(volatile char *)0x109;
  dire=(volatile char*)0x2D;
  oute=(volatile char*)0x2E;
  *dirL=0x00;
  *inL=0x00;
   *dire=0xFF; //set ddr of pin 5;for 0c0a
  *oute=0x00;
  Serial.println("pin configuration is succesfull");
}

void set_echo_pin(void)
{
  volatile char *tccr4b,*timsk4,*tcnt4h,*tcnt4l;
  tccr4b=(volatile char*)0xA1;
  timsk4=(volatile char*)0x72;
  //tcnt4h=(volatile char*)0xA5;
  //tcnt4l=(volatile char*)0xA4;

  
 // *tcnt4h=0x00;
 // *tcnt4l=0x00;
  *tccr4b=0x42;//setting prescalar(8,so for 1 tick 0.5 mic.s delay)and +ve edge detect
  *timsk4=0x20;//setting the innterupt mask flag for icp4.
  Serial.println("echo pin is set succesfull");
}



ISR(TIMER4_CAPT_vect)
{
  
volatile char*icr4l,*icr4h,*tcnt4h,*tcnt4l;
volatile  uint8_t x,y;

  icr4l=(volatile char*)0xA6;
  icr4h=(volatile char*)0xA7;
  //tcnt4h=(volatile char*)0xA5;
 // tcnt4l=(volatile char*)0xA4;
volatile long duration=0;
  *tcnt4h=0x00;
  *tcnt4l=0x00;
  x=*icr4l;     //assigning lower register value to variable x;
  y=*icr4h;     //assigning higher regiater value to variable y;
  duration=((y<<8)|x)*0.5;   //combining both register and make it as 16 bit.
  //Serial.println(duration);
  distance=duration*0.034/2;
  Serial.print(distance);
  Serial.print("  cm");
  Serial.println();
}

void setup() 
{
  Serial.begin(9600);
  set_trigger_pin();
  pin_configure();
  set_echo_pin();
  sei();//to enable gloabal intterupt;
  Serial.println("overall setup() is successful");
}

void loop() 
{
  volatile long x,i;
 volatile char*inl=0x109;
 x=*inl;
 for(i=0;i<100000;i++);
 Serial.print("the value at the echo pin:");
 Serial.print(x);
 Serial.print(" state");
 Serial.println();
 for(i=0;i<100000;i++);

}