Pseudocode for BeaconService.c

Module level variables:

volatile static unsigned int PeriodR;
volatile static unsigned int PeriodL;
static unsigned int LastRisingEdge;
static unsigned int LastFallingEdge;
static int BeaconsSensed = NeitherSensed;
static int BeaconNumber = 0;


InitBeaconService

Initialize the standard timer library
Turn the timer system on
Set the pre-scale to /128  
Set prescale to /16
Set to capture rising edge for T0 and falling edge for T1		
Set TIOS to capture pins 0 and 1 on port T 
Clear all flags
Enable associated capture interrupts on T0 & T1
Enable interrupts
    
Initialize timer to run at 1ms and time out at 50ms
Post the initial transition event

ES_EVENT RunBeaconService
Local variables: 	int i
  			ES_Event ReturnEvent;
  			ReturnEvent.EventType = ES_NO_EVENT; 



   
If EventType is ES_TIMEOUT       
         Sample the Beacon Sensors
	
	If either period is within range of interest
		For i = 0,  i less than 5
			Call beacon check function. Else post neither aligned 
      			Increment i 
			If beacon check function returns 1
				Break out of for loop
			End if
		End for
	End if
	
	Else update BeaconsSensed to NeitherSensed
	
        Reset PeriodR and PeriodL to 0
           
	Reset the timer to 50ms
       
      	Break and return ReturnEvent



   
       
       
Global Functions:

Int QueryBeacons
	Return BeaconsSensed

Int QueryBeaconNumber
	Return BeaconNumber



Local Functions:

Void BeaconCheck(Int CurrentBinTested):

Function Level Variables:
unsigned int LowerThreshold;
unsigned int UpperThreshold;

If CurrentBinTested is 1
	Assign proper thresholds for bin 1
Else if CurrentBinTested is 2
	Assign proper thresholds for bin 2
Else if CurrentBinTested is 3
	Assign proper thresholds for bin 3
Else if CurrentBinTested is 4
	Assign proper thresholds for bin 4

If PeriodL is greater than LowerThreshold and Period L is less than UpperThreshold
And PeriodR isgreater than LowerThreshold and Period R is less than UpperThreshold
	BeaconsSensed is equal to BothSensed;  
      	BeaconNumber is equal to CurrentBinTested;

Else if PeriodL is greater than LowerThreshold and PeriodR is less than UpperThreshold
	BeaconsSensed is equal to LeftSensed;
      	BeaconNumber is equal to CurrentBinTested;
Else if PeriodR is greater than LowerThreshold and PeriodR is less than UpperThreshold
	BeaconsSensed is equal to RightSensed;
      	BeaconNumber is equal to CurrentBinTested;



void interrupt _Vec_tim0ch4 RespToPhotoTransistorL(void)

Local variables:
unsigned int CurrentTime;
   
Clear the interrupt flag
Update CurrentTime
Update PeriodL to CurrentTime – LastRisingEdge
Update LastRisingEdge to CurrentTime   


void interrupt _Vec_tim0ch5 RespToPhotoTransistorR(void)

Local variables:
unsigned int CurrentTime;
   
Clear the interrupt flag
Update CurrentTime
Update PeriodR to CurrentTime – LastFallingEdge
Update LastFallingEdge to CurrentTime