//ECE 476 Final Project
//Cooler-Bot Mobile Unit Code
//Dan Lee and Robert Zimmerman

#include <Mega16.h>

char mode = 2; //start in receive mode
char received = 0; //pulse received flag

int transleft = 0; //transmit counter

signed char Ain[8]; //A/D conversion history
char Ainptr = 0;  //pointer to history location
int ainavg = 0;   //average value of history

unsigned char ADReady = 0;	//conversion ready flag

unsigned int time1; //timeout counters 

#define t1 1   //short timer


//Timer0 compare match ISR
interrupt [TIM0_COMP] void timer0_compare(void)
{										
    
    char a; //loop variable

    time1 = t1; //reset the timer

    switch (mode)
    {
    //transmit mode
    case 1: 	
        if (transleft == 1900) //transmit for 100, then wait 1900 ticks (stabilizes speaker)
        {
            PORTC.0 = 0;  //turn off MOSFET
            TCCR2 = 0b00001010; //turn off OC2 output
        }
        if (--transleft == 0)   //at end of timeout
        {  
            PORTC.0 = 0;   //keep MOSFET off
            mode = 2;      //go back to listening
            ainavg = 0;    //reset A/D averager
            
            received = 0;  //reset received flag

            //reset history
            for ( a = 0; a < 8; a++)
                Ain[a] = 0;

            //start convertin'
            ADCSRA = 0b11001100; 
        }
        break;
    
    //receive mode
    case 2: 
        //if stable pulse received
        if (received >= 15)
        {
            mode = 1; //go to transmit mode
            received = 0; //reset flag
            
        }
        break;
        
        
    }
    
}  


//ADC Ready ISR
interrupt [ADC_INT] void adcready()
{
    ADReady = 1;		
}


void main(void)
{
    signed char read, dummy;
    
    DDRD = 0x80;  //PORTD7 = OC2, PORTD2 = 23.8kHz square wave from OC0
    DDRB = 0xff;  //PORTB3 = OC0
    DDRC = 0xff;  //PORTC0 = MOSFET control
    PORTB = 0x00; //initilize
    PORTC = 0x00;
    
    
    //set up timer 0 and 2
    TIMSK=2;		//turn on cmp match ISR 
    OCR0 = 41;		//28kHz
    TCCR0=0b00011010;
    OCR2 = 41;	
    TCCR2=0b00001010;

    //init the task timers
    time1=t1; 
    
    //init the A to D converter 
    ADMUX = 0b01101001; 	 
    //enable ADC and set prescaler to 1/8
    //and start a conversion
    ADCSRA = 0b11001011;  
    
    //crank up the ISRs
    #asm
        sei
    #endasm  
        
        
        // main loop
        while (1)
        { 
            while (!ADReady) //wait for A/D conversion
                ;
            
            read = ADCH; //read it
            
            //update history pointer
            if (++Ainptr == 8)
            {
                Ainptr = 0;
            }
            
            //save cycles by updating average by subtracting the oldest
            //conversion and adding the newest
            ainavg -= Ain[Ainptr];


            //this "multiplies" the input signal by the reference 23.8kHz signal
            if (PIND.2) Ain[Ainptr] = read;  else Ain[Ainptr] = -read;

            //save the new result
            ainavg += Ain[Ainptr];
            
            //correlation of 10 required for detection
            //use positive and negative penalties to avoid false triggering
            if (ainavg > 10 || ainavg < -10) {
                received += 3;
                
            }
            else if (received)
            {  
                received--;
                
            }
            

            //if pulse not yet detected, keep convertin'
            if (received < 15)	{
                ADCSRA = 0b11001100;
            }
            else
            {
                transleft = 2000; //start a transmission
                PORTC.0 = 1;  //turn on MOSFET
                TCCR2=0b00011010;  //turn on OC2
                
            }
            
            ADReady = 0; //wait for conversion
        }
}