////////////////////////////////////////////////////////////////////////
////                             sonic_c.C                           ////
////                                                                 ////
////  Ultrasonic distance measure uses of timer0 and interrupts  
//   receives sonic to measure as a character on rs232
//    transmits results as a character on rs232
/// count@ counts no of 0.1ms interrupts while echo high
    //// scount1, scount2 hold distance, value 0(near)-170(far)
//  output to sonic on pin D0,D1,D2
//  input from sonic B1,B2,B3
//  shows results on led D3,D4,D5 if object < 30cm from sonic transmitter
/////////////////////////////////////////////////////////////////////////
#include <16F877.h>

#fuses HS,NOWDT,NOPROTECT

#use delay(clock=20000000)
#use RS232(baud=9600,xmit=pin_C4,rcv=pin_C3)
byte count1,count2,count3;
byte scount1,scount2,scount3;
byte turn;
#INT_RTCC
clock_isr(){
	//Now read the inputs to see if a sonic has echoed

	if (input(PIN_B1)) count1++;
	if (input(PIN_B2)) count2++;
	if (input(PIN_B3)) count3++;

}
	


main() 
{
	
	short s1,s2,s3;
	byte d_ready,thresh;

	output_low(PIN_D0);
	output_low(pin_D1);
	output_low(PIN_D2);
	s1=0;
	s2=0;
	s3=0;
	
	thresh=50;  //initial threshold for lighting leds
	setup_counters(RTCC_INTERNAL,RTCC_DIV_2);
	enable_interrupts(INT_RTCC);
	disable_interrupts(GLOBAL);

	turn=1;
	count1=0;
	count2=0;
	count3=0;

//show 3 leds working
	output_high(PIN_D3);
	output_low(PIN_D4);
	output_low(PIN_D5);
	delay_ms(100);
	output_low(PIN_D3);
	output_high(PIN_D4);
	output_low(PIN_D5);
	delay_ms(100);
	output_low(PIN_D3);
	output_low(PIN_D4);
	output_high(PIN_D5);
	delay_ms(100);
	output_low(PIN_D3);
	output_low(PIN_D4);
	output_low(PIN_D5);
	
	d_ready=2;

	do{
		if (d_ready==2) turn=getc();
		if (d_ready==2)
		{
			if (turn==1) 
			{
				output_high(PIN_D0);
				delay_us(20);
				output_low(PIN_D0);
				s1=0;
			}
			if (turn==2) 
			{
				output_high(PIN_D1);	
				delay_us(20);
				output_low(PIN_D1);
				s2=0;
			
			}
			if (turn==3)
			{
				output_high(PIN_D2);
				delay_us(20);
				output_low(PIN_D2);
				s3=0;
			}
			
			d_ready=0;
			enable_interrupts(GLOBAL);
			if (turn==255)
			{  //set led on threshold
				d_ready=2;
				disable_interrupts(GLOBAL);
				thresh=getc();
			}
		}

		if (d_ready==0)
		{
			if (turn==1)
			{
				if ((input(PIN_B1)) && (s1==0))
				{
					//Catch high transition, start of echo received
					count1=0;
					s1=1;
				}
				if ((!input(PIN_B1)) && (s1==1))
				{
					//Update counter on low pulse
					scount1=count1;
					s1=0;
					d_ready=1;
				}
				if (count1>250)
				{
					scount1=count1;
					d_ready=1;
				}
		
			}
			if (turn==2)
			{
				if ((input(PIN_B2)) && (s2==0))
				{
					//Catch high transition, start of echo received
					count2=0;
					s2=1;
				}
				if ((!input(PIN_B2)) && (s2==1))
				{
					//Update counter on low pulse
					scount2=count2;
					s2=0;
					d_ready=1;
				}
				if (count2>250)
				{
					scount2=count2;
					d_ready=1;
				}
			}

			if (turn==3) 
			{
				if ((input(PIN_B3)) && (s3==0))
				{
					//Catch high transition, start of echo received
					count3=0;
					s3=1;
				}
				if ((!input(PIN_B3)) && (s3==1))
				{
					//Update counter on low pulse
					scount3=count3;
					s3=0;
					d_ready=1;
				}
				if (count3>250)
				{
					scount3=count3;
					d_ready=1;
				}
			}
		}
//now scount1 and scount2 have echo values
	if (d_ready==1)
	{
		disable_interrupts(GLOBAL);
		if (turn==1) 
		{
			if (scount1<thresh) output_high(PIN_D3); else output_low(PIN_D3);	
			putc(scount1);
		}
		if (turn==2) 
		{
			if (scount2<thresh) output_high(PIN_D4); else output_low(PIN_D4);	
			putc(scount2);
		}
		if (turn==3) 
		{
			if (scount3<thresh) output_high(PIN_D5); else output_low(PIN_D5);	
			putc(scount3);
		}
		
		d_ready=2;
		
	}

	}while(TRUE);
}