/***************************************************************************

IRSensor.c

ME 218B Project Hats Off

Team Firefox

March 7, 2010

This senses the IR

PT4 of E128, Timer1, channel 4: IR sensor

AD7 of E128: IR sensor

***************************************************************************/

/*-------------------------- Include Files -----------------------------*/

#include "IRSensor.h"

/*-------------------------- Module Cals -----------------------------*/

const static unsigned int Black_Range = 380; //Analog reading of lowest value of black tape

const static unsigned int High_Period_Value = 20000; //Upper range of valid period

const static unsigned int Low_Period_Value = 18000; //Lower range

/*-------------------------- Module Vars -----------------------------*/

static unsigned int uPeriod; //Logs the period between IR pulses

static unsigned int FlagTime; //Helps timeout interrupt

static unsigned int TapeReads[10];

static unsigned int timeLastTapeRead = 0;

static unsigned int TapeIndex = 0;

/*-------------------------- Module Code -----------------------------*/

//Use Timer1 writing to channel 4 set to PT4 E128 for IR sensor

void initIRSensing(void) {

//input capture

DDRT &= BIT4LO;

TIM1_TSCR1 = _S12_TEN; //Turn on timer system to allow IC

TIM1_TSCR2 = TIM1_TSCR2 & ~(_S12_PR2 | _S12_PR1 | _S12_PR0); //pre-scale /1 = 24.0MHz

/* Set up IC4 to capture falling edges of PT4*/

TIM1_TCTL3 |= _S12_EDG4B; //falling edge

TIM1_TFLG1 = _S12_C4F; //Clear IC4 flag

TIM1_TIE |= _S12_C4I; //Enable IC4 interrupt

EnableInterrupts; //Globally enable interrupts

MyTimer_Init(); //Make sure 1 ms timer is running

timeLastTapeRead = MyTimer_GetTime();

}

//Interrupt Response Routine is called when TFLG1bit4 is set

//meaning interrupt of rising edge has occurred

void interrupt _Vec_tim1ch4 IRSensorICRoutine(void){

static unsigned int lastEdge;

PTT ^= BIT7HI; //For scope debugging

FlagTime = MyTimer_GetTime(); //Get FlagTime

uPeriod = TIM1_TC4 - lastEdge; //TC4 = clock tick count in an IR pulse

lastEdge = TIM1_TC4;

TIM1_TFLG1 = _S12_C4F; //Clear IC4 flag

}

//If IR signal uPeriod is in valid range, we are aligned with Beacon

char isAlignedWithBeacon(void){

if ((uPeriod < High_Period_Value) && (uPeriod > Low_Period_Value)){

return TRUE;

}

return FALSE;

}

void checkIRSensing(void){

unsigned int myTime;

myTime = MyTimer_GetTime();

if ((myTime - FlagTime) > 50) {

//It's been too long, an edge should have occured, timeout period measurement

uPeriod = 0;

}

}