Help with DT's 16-bit averaging subroutine?

[jellis00]

I am trying to get DT's 16-bit averaging subroutine to work correctly. I created the attached code as a way to test it. As you can see from the code, it writes values at various locations in the code to EEPROM so that after each execution I can read the data from the EEPROM as a way to see what values are being created.
What I don't undestand and am asking for help from anyone on this forum is why the variable VALUE is always showing up as zero (EEPROM addresses 19 and 36). By the way I set up this test routine, starting with a decimal value of 35260 and incrementing it 6 times, the average stored in VALUE should be 35263...not zero.
Any help is appreciated on this.

'*****************************************************************
'*  Name    : TEST_AVERAGE2.BAS                                  *
'*  Author  : John R. Ellis                                      *
'*  Notes   : Adapted from code by Darrel Taylor                 *  
'* "This routine will keep a "Running Average.                   *
'* Instead of adding a bunch of values together and then dividing*
'* by the number of samples, it averages each sample into the    *
'* final result immediately. This eliminates the need for 32 bit *
'* math.                                                         *
'* To allow it to "Catch up" to large changes, set the FAspread  *
'* to an acceptable range. Simply place the new number in VALUE  *
'* and GoSub AVERAGE  The Average will be returned into the same *
'* variable VALUE."                                              *
'*  Memory  : 546 Words of program memory required               *
'*****************************************************************
ADavg    VAR  WORD
AvgCount CON  16		' = Number of samples to average
FAspread CON  1000	' = Fast Average threshold +/-
i        VAR Byte        ' Index for measurment loop
pw       VAR WORD        ' Stores each pw measurment
pw0      Var pw.BYTE0    ' LSB of pw value
PW1      var PW.BYTE1    ' MSB of pw value
range    VAR WORD        ' Stores calculated range value
range0   VAR range.Byte0 ' LSB of range value
range1   VAR range.Byte1 ' MSB of range value
us_inch  con 147         ' Scale factor converts sensor 147 microsecs to inches
VALUE    VAR WORD        ' Stores average of measurements
value0   VAR value.byte0 ' LSB of value
value1   VAR value.byte1 ' MSB of value 

GOTO Main               ' Jump over Subroutines
 
' -----------------{ Subroutines }----------------------------------------
Average_Single:
    'Embedded use of Darrel Taylor's 16 bit averaging routine
    ' USE INTRUCTIONS: First, Select the sensor. ie.  Sensor = Temperature
    ' then place the new number in VALUE and then GoSub AVERAGE_SINGLE.
    ' The Average will be returned into the same variable VALUE.
        
    IF Value = ADavg Then NoChange
    IF ABS (Value - ADavg) > FAspread OR Value < AvgCount Then FastAvg
    IF ABS (Value - ADavg) < AvgCount Then RealClose
    ADavg = ADavg - (ADavg/AvgCount)
    ADavg = ADavg + (Value/AvgCount)
    GoTo AVGok
 
  FastAvg:
    ADavg = Value
    GoTo AVGok
 
  RealClose:
  'If averaging less than 8 samples, change AvgCount/4 to AvgCount/2.
    ADavg = ADavg - (ADavg/(AvgCount/2))
    ADavg = ADavg + (Value/(AvgCount/2))
 
  AVGok:
    Value = ADavg   ' Put Average back into Value
 
  NoChange:
Return

'--------------------------------------
Main:
   'DEFINE WRITE_USED 1 'Required if only writing WORD variables in version 2.6
    pw = 35260
    WRITE 32,pw                ' Comment out for test only
    For i = 0 to 5
        'PULSIN PORTA.4,1,pw   ' Make 5 measurements from PW pin 
                               ' of transceiver into array pw(i)
                               ' with running average in value
        pw = pw +1                 ' Simulates pw measurement
        WRITE 34,pw            ' Comment out for test only
        Value = pw
        WRITE 36,VALUE         ' Comment out for test only
        'Running average in value...Max pw = 20' = 240" = 35280 usec. Therefore
                                   'pw, value, & range are 16 bit WORDs.
        GOSUB Average_Single
    NEXT
    WRITE 17,i                 ' Comment out for test only
    WRITE 19,VALUE             ' Comment out for test only
    range = (Value / us_inch) +1   ' Convert value to range in inches (max 240)
                                   ' add 1 to account for division rounding.
    WRITE 21,range      ' Store day's range in EEPROM location
END

[Darrel Taylor]

If you want to write WORD variables to EEPROM, you need to either add the WORD modifier to the WRITE statement, or WRITE the lowbyte and highbyte seperately in 2 WRITE statements.

WRITE 36,WORD VALUE

[jellis00]

OK, Darrel,...that is one stupid mistake on my part. But I fixed the WRITE statements per the attached code, and VALUE is still coming out of the subroutine with a value of zero, as evidenced in the EEPROM WRITE address 19. Yet when I WRITE to EEPROM address 36 within the loop where the subroutine is called, the values in VALUE are correct going into the averaging subroutine.
I still can't figure out why the averaging isn't working?? Any ideas?

'*****************************************************************
'*  Name    : TEST_AVERAGE2.BAS                                  *
'*  Author  : John R. Ellis                                      *
'*  Notes   : Adapted from code by Darrel Taylor                 *  
'* This routine will keep a "Running Average".                   *
'* Instead of adding a bunch of values together and then dividing*
'* by the number of samples, it averages each sample into the    *
'* final result immediately. This eliminates the need for 32 bit *
'* math.                                                         *
'* To allow it to "Catch up" to large changes, set the FAspread  *
'* to an acceptable range. Simply place the new number in VALUE  *
'* and GoSub AVERAGE  The Average will be returned into the same *
'* variable VALUE.                                               *
'*  Memory  : 546 Words of program memory required               *
'*****************************************************************
ADavg    VAR  WORD
AvgCount CON  16		' = Number of samples to average
FAspread CON  1000	' = Fast Average threshold +/-
i        VAR Byte        ' Index for measurment loop
pw       VAR WORD        ' Stores each pw measurment
pw0      Var pw.BYTE0    ' LSB of pw value
PW1      var PW.BYTE1    ' MSB of pw value
range    VAR WORD        ' Stores calculated range value
range0   VAR range.Byte0 ' LSB of range value
range1   VAR range.Byte1 ' MSB of range value
us_inch  con 147         ' Scale factor converts sensor 147 microsecs to inches
VALUE    VAR WORD        ' Stores average of measurements
value0   VAR value.byte0 ' LSB of value
value1   VAR value.byte1 ' MSB of value 

GOTO Main               ' Jump over Subroutines
 
' -----------------{ Subroutines }----------------------------------------
Average_Single:
    'Embedded use of Darrel Taylor's 16 bit averaging routine
    ' USE INTRUCTIONS: First, Select the sensor. ie.  Sensor = Temperature
    ' then place the new number in VALUE and then GoSub AVERAGE_SINGLE.
    ' The Average will be returned into the same variable VALUE.
        
    IF Value = ADavg Then NoChange
    IF ABS (Value - ADavg) > FAspread OR Value < AvgCount Then FastAvg
    IF ABS (Value - ADavg) < AvgCount Then RealClose
    ADavg = ADavg - (ADavg/AvgCount)
    ADavg = ADavg + (Value/AvgCount)
    GoTo AVGok
 
  FastAvg:
    ADavg = Value
    GoTo AVGok
 
  RealClose:
  'If averaging less than 8 samples, change AvgCount/4 to AvgCount/2.
    ADavg = ADavg - (ADavg/(AvgCount/2))
    ADavg = ADavg + (Value/(AvgCount/2))
 
  AVGok:
    Value = ADavg   ' Put Average back into Value
 
  NoChange:
Return

'--------------------------------------
Main:
   'DEFINE WRITE_USED 1 'Required if only writing WORD variables in version 2.6
    pw = 35260
    WRITE 32,WORD pw           ' Comment out for test only
    For i = 0 to 5
        'PULSIN PORTA.4,1,pw   ' Make 5 measurements from PW pin 
                               ' of transceiver into array pw(i)
                               ' with running average in value
        pw = pw +1                 ' Simulates pw measurement
        WRITE 34,WORD pw       ' Comment out for test only
        Value = pw
        WRITE 36,WORD VALUE    ' Comment out for test only
        'Running average in value...Max pw = 20' = 240" = 35280 usec. Therefore
                                   'pw, value, & range are 16 bit WORDs.
        GOSUB Average_Single
    NEXT
    WRITE 17,i                 ' Comment out for test only
    WRITE 19,WORD VALUE        ' Comment out for test only
    range = (Value / us_inch) +1   ' Convert value to range in inches (max 240)
                                   ' add 1 to account for division rounding.
    WRITE 21,WORD range        ' Store day's range in EEPROM location
END

[Darrel Taylor]

Maybe you've worn out your EEPROM.
I never liked that debugging method.

I've run it here and it works fine on a 16F887.

Here's a run in Proteus.



And here's a readback from a real chip running the same program.