There is some overkill for robustness in this code.  The pulse in command 
alone could read the sensors but if it didn't see anything it would be 
stuck for some time just doing the read.  have fun.



'For basic stamp 1
'By bob gross
'7/15/97

'Symbol Probability = B5
'Sensor to read = B6
'Frequency = B3 at end of code, used for loop counter in ReadPulseIn
'B6 is used to pass the IR sensor number one desires to look at

Top:
Serin 0,N2400,#B6        'Wait for a command from external computer
'Pause 10
        'Reset to 0 before calling sub(s)
        B5 = 0: B9 = 0: B2 = 0: B3 = 0: W4 = 0: W5 = 0
        
If B6 < 1 OR B6 > 6 Then SkipAll   'Skip if not a valid sensor number
'       Pause 10

'pause 100

B6 = B6 + 1     'Set B6 to the correct pin numbers before calling sub


'If jumper is x then Goto SerialMode
'If jumper is x then Goto ParMode
'If jumper is x then Goto ControlerMode

'LookForPulse:
'This next rutine sorts out which pin to look at for activity.
'It then looks at the proper pin for activity.  
'When it is the proper pin then skips the rest of the rutine
' to "DoneLookingAtPin"
'Then it is measured for pulse width. 
'Toggle 0
        If B6 > 2 Then SkipPin2         'Use for forward facing sensor
                For B3 = 1 to 100                'Sensor on pin 2
                        B5 = B5 + Pin2  'Remember pins are base 0
                Next B3
        Goto DoneLookingAtPin           
        SkipPin2:
        
        If B6 > 3 Then SkipPin3         'Use for forward facing sensor
                For B3 = 1 to 100                'Sensor on pin 3
                        B5 = B5 + Pin3
                Next B3
        Goto DoneLookingAtPin

        SkipPin3:
        If B6 > 4 Then SkipPin4 
                For B3 = 1 to 100                'Sensor on pin 4
                        B5 = B5 + Pin4
                Next B3
        Goto DoneLookingAtPin

        SkipPin4:
        If B6 > 5 Then SkipPin5 
                For B3 = 1 to 100                'Sensor on pin 5
                        B5 = B5 + Pin5
                Next B3
        Goto DoneLookingAtPin

        SkipPin5:
        If B6 > 6 Then SkipPin6 
                For B3 = 1 to 100                'Sensor on pin 6
                        B5 = B5 + Pin6
                Next B3
        Goto DoneLookingAtPin

        SkipPin6:
                For B3 = 1 to 100        'If I got this far must be pin 7
                        B5 = B5 + Pin7  'Remember pins are base 0
                Next B3
        DoneLookingAtPin:
        'Toggle 0
        B5 = 100 - B5            'Convert to 0 = no probability, 100 = max
'                GoSub ReadPulseIn
'                Return


'ReadPulseIn:
'This rutine first checks if there was activity on pin.  
'If so it then looks for valid pulse signal for measurement.
'First the negitive width is measured.  Then if the negitive width
'was valid, it then measures the positive width.  It continues this
'until the pulse is measured twice for negitive and twice for positive.
'It then compares the pusles for consistancy.  If not consistance it 
'then discards them (filter).  If consistant it averages them.  It then
'returns with a valid measurement for both period and probability.
  
        B3 = 0                  'Reset B3 to zero 
        If B5 < 40 Then SkipRPI  '(active low sensor) Skip If not low
                          'At least two out of nine counts saw something 
        Pulsin B6, 0, B4        'Read the negitive pulse in
     If B4 < 30 Then SkipRPI 'If the negitive wasn't their then skip, else
        Pause 1
        Pulsin B6, 1, W4        'Read the positive pulse width
     If B4 < 30 Then SkipRPI 'If the positive wasn't their then skip, else
        W4 = W4 + B4         'Combine the negitive and positive widths
        Pause 2
        Pulsin B6, 0, B4        'Read the negitive pulse width a 2nd time
     If B4 < 30 Then SkipRPI 'If the negitive wasn't their then skip, else
        Pause 3
        Pulsin B6, 1, W5     'Read the positive pulse width a 2nd time
     If B4 < 30 Then SkipRPI 'If the positive wasn't their then skip, else
        W5 = W5 + B4         'Combine the 2nd negative and positive widths
                             'for later filter and average
        If W5 > W4 Then FirstIsHigher '
        B3 = W4 - W5            'Look at the variance in data.  
        If B3 <15 Then PulseGood 'Closer than 15 counts is valid data
        W4 = 0                  'Reset words if data isn't valid
        W5 = 0                  'This filters out bad data
        FirstIsHigher: 
        B3 = W5 - W4            'Find out if data is valid
        'NOTE: If W4 & W5 were set to 0 by the first they remain 0.
        If B3 <15 Then PulseGood 'Closer than 15 counts is valid data
        SkipRPI:                'Skip Read Pulse In
        W4 = 0                  'Reset words if data isn't valid
        W5 = 0
        PulseGood:              'The data at this point is valid
        W5 = W4+W5/2            'Average the readings for accuracy
        If W5 > 80 Then Valid    'If more 80 the data is valid else
        W5 = 0                  'Else reset W5
        Valid:
        B3 = W5                'Need number in byte form to send out RS-232


'Return
'GoSub LookForPulse

SkipAll:
'debug b3
'Debug b5
SerOut 1, N2400,(B3)     'Send out frequency's period in counts of 10 uS
SerOut 1, N2400,(B5)     'Send out duty cycle in counts of 1 to 99

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