/* This program xmtbyte for the IRX 2.0 board with PIC16C84 uses the IR
 * transmitter to repeatedly send out a 3 byte address which 
 * corresponds to a Media Lab room number. Additionally this program,
 * listens for the IR receiver and will upload one byte of information
 * appending this to the transmitted signal. The beacon will continue
 * to emit this new signal until it recieves verification of the message,
 * in the form of the same byte again.
 * 
 * Writen by Dana Kirsch 
 * 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 for port B */
#use RS232(BAUD=2400,XMIT=PIN_7,RCV=PIN_11)
 					/* Possibly for putchar */
					
#define RED_LED	PIN_8			/* Port definitions */
#define IR_XMT	PIN_9
#define IR_RCV	PIN_10

#define RTCC_PERIOD 160			/* Timing; want 104 uSec 'tics.' */

#define offIR 	OUTPUT_HIGH(IR_XMT)	/* High turns IR_LED off */
#define onIR  	OUTPUT_LOW(IR_XMT) 
#define onRED 	OUTPUT_LOW(RED_LED)
#define offRED	OUTPUT_HIGH(RED_LED)

#define FLOOR 0x00
#define ROOM  0x5F
#define LETTER 0x55

	
/* =========================== 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 = 1650us */
		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) {		/* IRstopbit = 100us */
		DELAY_US(100);
	}
}

#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[4];			/* IR output buffer of 4 bytes */

send_packet()				/* Send the IR information packet */
{
	int x;
	ircheck = 1;
	IRsendbyte(1);			/* First send a one */
	for(x=0; x<4; x++){		/* Send the four bytes of info */
		IRsendbyte(irXmtData[x]);
		ircheck = ircheck^irXmtData[x];
	} if (ircheck == 1) ircheck = 2;
	IRsendbyte(ircheck);		/* Last, the error checking byte */
}

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

int irBit;
int irBits=0;
int irClk=0;
int irRcv[1];				/* Buffer for message received */
int irLast=1;
int irOut;
int sendRcvState=0;			/* Var for I/O state */
int dataInMemory=0;			/* State of post-it data */

#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;
      sendRcvState = 1;
     }
  } if (irClk > 250) { 
    sendRcvState = 0;
    if (dataInMemory == 1) {
    	dataInMemory = 2;
    } else if (dataInMemory == 3) {
  	dataInMemory = 0;
    }
  } if (irBits == 8) {			
    irBits = 9;
    irOut = irRcv[0];
  }
  irLast = irBit;
}

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

int s, m;
int ercheck;
int irRcvData;
int tmpMemory=9;

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 is zero */
	irXmtData[0] = FLOOR;	/* Read data in eeprom to array */
	irXmtData[1] = ROOM;
	irXmtData[2] = LETTER; 
	irXmtData[3] = 0x00; 

	ENABLE_INTERRUPTS(GLOBAL);	/* Activates interrupt */
		
	while (1) {				/* Main loop */
	  if (sendRcvState == 0) {
		 	send_packet(); 
		  } 
	     for(m=1; m <7 ; m++)
	     {
	     if (irBits == 9) {
	  	irBits = 0;
	  	if (s == 0 && irOut == 1) { 
			ercheck = irOut;		/* First recieve a one */
			s = 1;
		} else if (s == 1) {
			irRcvData = irOut;	/* Then the byte of data */
			ercheck = ercheck ^ irOut; 
			s = 2;
		} else if (s == 2) {
			if (ercheck == 1) ercheck = 2;
			if (irOut == ercheck) {		/* Match the check byte */
			  if (tmpMemory == irRcvData) {
			    if (dataInMemory == 0) {
			    	irXmtData[3] = irRcvData; 	/* Upload data */
				sendRcvState = 0;
				dataInMemory = 1;
			
			    } else if (dataInMemory == 1) { /* Do nothing */
			    	sendRcvState = 0;
			    } else if (dataInMemory == 2) { /* Reset */
			     	irXmtData[3] = 0x00;
			     	sendRcvState = 0;
			        dataInMemory = 3;
			
			    } else sendRcvState = 0;  		/* Do nothing */
			  } else tmpMemory = irRcvData; 	 /* Write info to memory */
			} s = 0;
		} else s = 0;
	  } 
	}

	

  	}
}