/*This is the receiver end program*/

#include <mega32.h>     
#include <stdio.h>
#include <stdlib.h>

#define begin {
#define end }  

// Declare your global variables here
unsigned char lastcommand,command,badcommand;      
unsigned char speed,lastspeed;
unsigned char dir, turn;
unsigned char count,reload;
unsigned int  time0,breakcount;   
unsigned char forward;       
unsigned char danger,distance;
unsigned char headlight,breaklight,forcebreak;  //for brakelight control  

//**********************************************************
//timer 0 overflow ISR
interrupt [TIM0_OVF] void timer0_overflow(void)
begin
   //reload to force 1 mSec overflow
   TCNT0=reload; 
   time0++;
   if (time0==67)
   {		
   		//start ADC conversion
    	ADCSR = 0xc7; 
        time0=0;
   }

 
end  
//**********************************************************
void initialize(void)
{
    //ADC input
    DDRA=0x00;

	//output headlight, brakelight
	PORTB=0xff;
	DDRB=0xff;

    //PORTC=0xff;
	DDRC=0xff;

	//output PWM & USART communication jumpers
	DDRD=0xff;

	// Timer/Counter 0 initialization
	time0=0;
	reload=256-125;
	TCCR0=0x03 ;
	TCNT0=reload;
  	OCR0=0x00;

	//Timer1 setting, used to output PWM signal
	TCCR1A=0x91;
	TCCR1B=0x02;
 
   	//UART setting
   	UCSRA=0x00;
  	UCSRB=0x10;
    UCSRC=0x36;
	//2400 baud 
	UBRRH=0x01;
 	UBRRL=0xa0;  

    //initialization of variable 
    lastcommand=0x55;
    dir=0;
    turn = 0;
	lastspeed=1;
	speed = 1;
	forward = 0; 
	danger = 0; 
	
	distance=0;
	breaklight=0;
	breakcount=0;  
	forcebreak=0;
        
	//choose PINA.0 as analog input
    ADMUX = 0x20;
        
    //enable timer0 
   	TIMSK=1;
    #asm("sei");
}

//**********************************************************        
void changespeed(void)
{	        
     //update lastspeed
     lastspeed=speed;        
     
     //change car speed according to command if no dangers detected 
     if ((!danger) || (!forward))
     {    
	 	switch (speed)
		{	
			case 0 : OCR1A=128;    //50%
				     break;
			case 1 : OCR1A=0;      //0%   
				     break;
			case 2 : OCR1A=191;    //75%
			         break;
			case 3 : OCR1A=255;    //100%
		             break;
     	}
     } 
     else OCR1A=0; // stop the car
}                        
	
//**********************************************************
void main(void)
{
      initialize();    
      
   
      
      while (1)
      { 
      		//polling receive complete flag, update command
      		if (UCSRA.7==1) 
			{ 
           		if (UCSRA.4==1) badcommand=UDR;
           		else command=UDR;
            }      
   
			//polling ADC complete flag detect obstacle
   			if (ADCSR.4==1)     
     		{ 	
         		distance=ADCH;
         		if (distance > 0x20)
         		{
         			danger=1; 
         			changespeed(); 
         			forcebreak=1;  
         		}
         		else if (danger==1) 
       			{
       				danger=0;    
         			forcebreak=0;
         			changespeed();
         		}
            }
          
            //see if command is changed  
 	  		if (lastcommand!=command)
     		{   
      			lastcommand = command;
      			//decode command
      			speed = (command & 0x03);
      	    	forward = (command & 0x10);
      			if (command & 0x08) dir=0 ;
      			else dir=1;
 				if (command & 0x04) turn=0;
 				else turn=1;     	   	        
      	   	
      	    	headlight = (command & 0x40);
      	    				
    			//change speed
       			if (speed!=lastspeed) 
       	  		{   
       	  			if (speed ==0x01) forcebreak=1;
       	  			else 
       	  			{ 	
						forcebreak=0;       	  						 	                  
      	                if (speed < lastspeed) 
      	                {
      	                    breakcount=7000;
      	      				breaklight=1;
      	      			}
      	      			else breakcount=0;
      				}		
      	            changespeed();        	 	   
      	 		}        
        	 }  
        	        
		 	 			
			 // brakelight control		
			 if (breakcount>0) breakcount--;
			 if ((!forcebreak) && (breakcount==0)) breaklight=0;   
			 if ( (forcebreak==1) || (breaklight==1)) PORTC.0=0;
			 else PORTC.0=1;
 	      
 		     //car control
 	         PORTD.2=dir;    
 	         PORTD.3=turn;
          	 PORTD.4=forward;	  
          			
          	 //headlight
          	 if (headlight) 
          	 {	
				PORTC.1=0;
          	  	PORTC.2=0;
          	 }
          	 else 
          	 {
          		PORTC.1=1;
          		PORTC.2=1; 
         	 }
              	    	
	} //end while         	    
     
                     
}   //end main