/* This program for an IRX 2.0 board with PIC16C84 uses the IR
 * reciever to detect the emmisions of various IR beacons placed throughout
 * the lab. It sends the results of this detection to the RS232 serial port.
 * Additionally, upon signal from the RS232, it transfers a single byte
 * message from the RS232 port up to the beacon via the IR LED.
 *
 * Writen by Dana Kirsch for April 2nd. 
 * Modified and implemented by Solomon Assefa
 * 
 */
 
#include <PIC16C84.H>			/* Use the PIC16C84 chip */  
#include <stdio.h>

/* Device has a 4Mhz clock [used by DELAY_MS() and DELAY_US()] */
#use DELAY(CLOCK=4000000)

#use FAST_IO(B)				/* Fast I/O switching of ports */
#use RS232(BAUD=2400,XMIT=PIN_7,RCV=PIN_11)
					/* Possibly to use the putchar */

#define RED_LED		PIN_8		/* Port B pin definitions */
#define IR_RCV		PIN_10
#define IR_XMT		PIN_9
#define SR_RCV		PIN_11
#define SR_XMT		PIN_7

#define offIR OUTPUT_HIGH(IR_XMT)	/* High turns IR_LED off */
#define onIR OUTPUT_LOW(IR_XMT) 
#define offRED OUTPUT_HIGH(RED_LED)	/* High turns off RED_LED */
#define onRED OUTPUT_LOW(RED_LED)
#define offSR OUTPUT_LOW(SR_XMT)	/* Low outputs a zero to SRport */
#define onSR OUTPUT_HIGH(SR_XMT)
	
#define RTCC_PERIOD 160			/* Each period is 104us */

/* =========================== MORSE CODE ========================== */

void flash_dit() {
	onRED;
	DELAY_MS(100);
	offRED;	
	DELAY_MS(100);
}

void flash_dah() {
	onRED;
	DELAY_MS(300);
	offRED;
	DELAY_MS(100);
}

void flash_space() {
	DELAY_MS(200);
}

/* ========================= IR OUT ========================= */

  IRburst(int D) {			/* Send one IR bit */
	int c;				/* Flash 5 times at 38KHz */
	for (c=0; c<10; c++) {
		onIR;			
		DELAY_US(6); 
		offIR;	
		DELAY_US(11); 
	}				/* Bit is pause between flashes */
					/* This conserves power */
	if (D == 0) {			/* IRstartbit = 1650 us */
		DELAY_MS(1);
		DELAY_US(250);
		DELAY_US(250);
		DELAY_US(150);
	} else if (D==1) {		/* IRonebit = 1100us */
		DELAY_MS(1);
		DELAY_US(100);
	} else if (D==2) {		/* IRzerobit = 550us */
		DELAY_US(250);		/* PCM problem with # > 255 */
		DELAY_US(250);
		DELAY_US(50);
	} else if (D==3) {
		DELAY_US(100);		/* IRstopbit = 2000us */
	}
}

#define IRstartbit IRburst(0)
#define IRonebit   IRburst(1)
#define IRzerobit  IRburst(2)
#define IRstopbit  IRburst(3)

IRsendbyte(int Z)			/* Construct and send one IRbyte */
{
        DISABLE_INTERRUPTS(GLOBAL);
        	IRstartbit;
        	if (((Z&0x01)     )==1) IRonebit; else IRzerobit;
        	if (((Z&0x02) >> 1)==1) IRonebit; else IRzerobit;
        	if (((Z&0x04) >> 2)==1) IRonebit; else IRzerobit;
        	if (((Z&0x08) >> 3)==1) IRonebit; else IRzerobit;
        	if (((Z&0x10) >> 4)==1) IRonebit; else IRzerobit;
        	if (((Z&0x20) >> 5)==1) IRonebit; else IRzerobit;
        	if (((Z&0x40) >> 6)==1) IRonebit; else IRzerobit;
        	if (((Z&0x80) >> 7)==1) IRonebit; else IRzerobit;
        	IRstopbit;
        ENABLE_INTERRUPTS(GLOBAL);
}

int ircheck;				/* Error checking variable */
int irXmtData[1];			/* IR output buffer of 1 byte */
send_ir_packet()			/* Send the IR information packet */
{
	int x;
	ircheck = 1;
	IRsendbyte(1);			/* First send a one */
	IRsendbyte(irXmtData[0]);       /* Send the byte of IR info */
	ircheck = ircheck^irXmtData[0];
	if (ircheck == 1) ircheck = 2;
	IRsendbyte(ircheck);		/* Finally send the error checking byte */
}

/* ========================= SERIAL OUT ========================= */

Sburst(int z)				/* Output one serial bit */
{
	if (z == 0) offSR;		
	else if (z == 1) onSR;
  	DELAY_US(400);			/* RS232 protocol delay */
}

#define Sstartbit Sburst(0)		/* Standard RS232 protocol */
#define Sonebit   Sburst(1)
#define Szerobit  Sburst(0)
#define Sstopbit  Sburst(1)

Ssendbyte(int Z)			/* Output one serial byte */
{
	/* RED_LED flashes during SR_out */
    	DISABLE_INTERRUPTS(GLOBAL);
	 Sstartbit;
	 if (((Z&0x01)     )==1) Sonebit; else Szerobit;
	 if (((Z&0x02) >> 1)==1) Sonebit; else Szerobit;
	 if (((Z&0x04) >> 2)==1) Sonebit; else Szerobit;
	 if (((Z&0x08) >> 3)==1) Sonebit; else Szerobit;
	 if (((Z&0x10) >> 4)==1) Sonebit; else Szerobit;
	 if (((Z&0x20) >> 5)==1) Sonebit; else Szerobit;
	 if (((Z&0x40) >> 6)==1) Sonebit; else Szerobit;
	 if (((Z&0x80) >> 7)==1) Sonebit; else Szerobit; 
	 Sstopbit;
    	ENABLE_INTERRUPTS(GLOBAL);
}

/* ========================= IR IN ========================= */

int srXmtData[4];			/* Buffer for 4 bytes to send */
int irBit;
int irBits=0;
int irClk=0;
int irRcv[1];				/* Buffer for message received */
int irLast=1;
int srOut;

#inline ir() {				/* IR script */
  irBit = INPUT(IR_RCV);
  irClk++;
  if (irBit == 0 && irLast == 1) {	/* Leading edge of 38KHz pulse*/
    if (irClk > 13 || irClk < 4) {	/* If the timing is off reset */
      irClk = 0;
      irBits = 0; 
    } else if (irClk > 9 && irBits < 8) {
      irBits++;
      SHIFT_RIGHT(irRcv, 1, 1);		/* Add a one if delay long */
      irClk = 0;
    } else if (irBits < 8) {
      irBits++;
      SHIFT_RIGHT(irRcv, 1, 0);		/* Add a zero if delay short */
      irClk = 0;
    }
  }
  if (irBits == 8) {			
    irBits = 9;
    srOut = irRcv[0];
  }

  irLast = irBit;
}

/* ========================= SERIAL IN ========================= */

int srBit;
int srBits=0;
int srRcv[1];				/* Buffer for Serial data received */
int srLast=1;
int irOut;
int sendRcvState=0;			/* Transmit SR until recieved */
int w;

#inline sr() {				/* Serial script */
  srBit = INPUT(SR_RCV);
  
  if (srBit == 0 && srLast == 1) {	/* Find the Startbit */
    DISABLE_INTERRUPTS(GLOBAL);
    DELAY_US(385);
    for(w=1; w<9; w++){		/* Catch the byte -- was 10 */
       srBit = INPUT(SR_RCV); 
      SHIFT_RIGHT(srRcv, 1, srBit);
      srBits++;
      DELAY_US(385);
    }  srBit = INPUT(SR_RCV);
    if (srBits == 8) {  		/* Confirm the Stopbit */
      srBits = 15;			/* Set the flag */
      irOut = srRcv[0]; 
	flash_dit(); 
    } ENABLE_INTERRUPTS(GLOBAL);
    sendRcvState=1;
  } else {
    sendRcvState=0;
  } srLast = srBit;
}      

/* ========================= MAIN =========================== */

#INT_RTCC interrupt_script() {		/* Run every time RTCC reaches zero */
    SET_RTCC(RTCC_PERIOD);		/* Reset countdown */
    ir();
    sr();
}

int s, m;
int c = 0;
int ercheck;				/* IR error check byte */

main()
{
    DISABLE_INTERRUPTS(GLOBAL);		/* Don't interrupt */
    SET_TRIS_B(0x30);			/* Set B out xpt (IR_RCV,SR_RCV) */
    SETUP_COUNTERS(RTCC_INTERNAL, WDT_18MS);
    ENABLE_INTERRUPTS(RTCC_ZERO);	/* Interrupt when RTCC = 0 */
    flash_dit();
    flash_dit();
    flash_space();
    flash_dah();
    flash_dit();
    ENABLE_INTERRUPTS(GLOBAL);		/* Activates enabled interrupt */ 

    
    while (1) {				/* Main loop */
	if (sendRcvState == 1) { 		/* Prepare to send IR */
	   if (srBits == 15) {
		 for(m=0;m<5;m++) /* was 10 */
		 {  
		srBits = 0;
		irXmtData[0] = irOut; 	      /* Buffer the byte of data */
		send_ir_packet(); 	      /* Upload the message */
		 } 
	   }
	}

	if (sendRcvState == 0) {	/*  No SR signal, Rcv IR */
	   if (irBits == 9) {
		irBits = 0;
		if (s == 0 && srOut == 1) {
					/* First recieve an IR one */
		  ercheck = srOut;
		  s = 1;         
		} else if (s >= 1 && s <= 4) {
   		  srXmtData[s-1] = srOut; 
		  ercheck = ercheck ^ srOut;
		  s++;
		} else if (s == 5) {
		  if (ercheck == 1) ercheck = 2;
		  if (srOut == ercheck) {
		  			/* Match the IR check byte */
			Ssendbyte(srXmtData[0]);
			Ssendbyte(srXmtData[1]);
			Ssendbyte(srXmtData[2]); 
			Ssendbyte(srXmtData[3]); 
		  } s = 0;
		} else s = 0;
	   }
	} 
    }
  }