Averaging AtoD samples

[Ioannis]

I suppose that you corrected the array definition from[6] to [5].

And then the check in the program:

If CounterA < 5 then goto SortLoop

to this:

If CounterA < 4 then goto SortLoop

Ioannis

[HankMcSpank]

Guy - what can I say .....I initially used random 1-6 for my numbers in the array & it sorted them & averaged them fine! (ie 1,2,3,4,5,6 was the screen output!)

I'm puzzled why my screen output posted above doesn't look like it's working (for either the sorting or the averaging!! lol) - it was late ...that's my lame excuse for not picking up on that! The 'sorting' part of the code was a direct lift from Melanie's article.

I'm at work now (don't tell my boss!) , so will revisit this tonight.

[HankMcSpank]

Ok, the thread title really ought to be called stripping out erroneous samples & then averaging the leftovers (vs averaging data which includes erroneous samples), I've revisited my earlier problem

@ __CONFIG _FCMEN_OFF & _HS_OSC & _WDT_OFF & _MCLRE_OFF & _CP_OFF & _IESO_OFF & _BOR_OFF & _PWRTE_OFF

DEFINE  OSC 20          ' set Oscillator at 20Mhz.
DEFINE  NO_CLRWDT 1   ' PBP doesn't clear WDT automatically
DEFINE HSER_CLROERR 1
DEFINE HSER_TXSTA 24h ' Enable transmit
DEFINE HSER_SPBRG 129 ' set USART to 9600 baud  @20Mhz

ANSEL       =  0
ANSELH     =  0

    CounterA            var Byte    'A counter for sorting out the erroneous data
    DataA               var word    'A Variable used in sorting the numbers in the array 
    RawData             var word [6] 'This is the RawData gojng into the array
    Averaged            var word     'This is used to get the average.
  
    top:    
    RawData[0]  = 300
    RawData[1]  = 100
    RawData[2]  = 200
    RawData[3]  = 600
    RawData[4]  = 400
    RawData[5]  = 500

    pause 250
  
    hserout [27,91,72]          'home cursor
    hserout [27,91,50,74]      'clear screen  
    
   next1:
    hserout [13,10]
    hserout [13,10]
    pause 300 
    hserout ["before....", 13, 10]
    hserout [13,10]
    hserout [dec rawdata[0],13,10]
    hserout [dec rawdata[1],13,10]
    hserout [dec rawdata[2],13,10]
    hserout [dec rawdata[3],13,10]
    hserout [dec rawdata[4],13,10]
    hserout [dec rawdata[5],13,10]
    hserout [13,10]
    hserout [13,10]

    pause 2000
    
    CounterA =0
    gosub SortArray
    gosub Average_data
    hserout ["after....", 13, 10]
    hserout [13,10]
    hserout [dec rawdata[0],13,10]
    hserout [dec rawdata[1],13,10]
    hserout [dec rawdata[2],13,10]
    hserout [dec rawdata[3],13,10]
    hserout [dec rawdata[4],13,10]
    hserout [dec rawdata[5],13,10]
    hserout [13,10]
    hserout ["therefore, middle two samples are ", dec rawData[2]," + ", dec rawData[3], 13,10]
    pause 500
    hserout [13,10]
    hserout ["averaged middle two samples = ", dec averaged,13,10]
    pause 500
    pause 3000
    goto top
    
    
Average_data:
    Averaged = (rawData[2]+rawData[3])/2    ' average the middle two of 6 samples
    return

SortArray:
SortLoop:
    If RawData(CounterA+1) < RawData(CounterA) then
        DataA=RawData(CounterA)
        RawData(CounterA)=RawData(CounterA+1)
        RawData(CounterA+1+0)=DataA
        If CounterA > 0 then CounterA=CounterA-2
        endif
    CounterA=CounterA+1
    If CounterA < 5 then goto SortLoop
    Return

    end

And it works (basically, the code throws away all but the middle two samples of six & averages those two - ideal if your input data is all over the place.,...eg comparator counts etc!)...

before....

300
100
200
600
400
500


after....

100
200
300
400
500
600

therefore, middle two samples are 300 + 400

averaged middle two samples = 350

Or a more real world example (eg a comparator interrupt count jittering in or around the 200 count level but with one spurious/erroneous count of 400 in the 'sample of six' to get rid of)...

before....

199
400
200
200
199
200


after....

199
199
200
200
200
400

therefore, middle two samples are 200 + 200

averaged middle two samples = 200

Not entirely sure what the problem was (I changed a few things at once & didn't retrace my steps!)

[aratti]

That's better!

Cheers

Al.

[HankMcSpank]

That's better!

Cheers

Al.

& thanks for offering up some help/support earlier!

[Plcguy]

In a different application I used a "weighted Average" where no one sample could mangle the running average.
This is the regurgitated conversion to PBP:

I initialize the values and add new value to the stack and subtract off the old average, giving the new value 1/weight of effect

I leave the running average in A2D counts to avoid rounding
Must watch (Max value * number of samples) < 65000


Weight var byte
WeightedAve var word
Ave var word
WeightedCounts
NewAve var word
Count var word

AveragingComplete var word

Incoming var word ‘incoming value from a2d
WeightedCounts=0
Weight = 100
AveragingComplete = 0
Ave=0

If Count=0 then WeightedCounts= incoming* Weight
If Count=0 then Ave= incoming

If Count < Weight then Count = Count + 1
NewAve =(incoming+ WeightedCounts-Ave
WeightedCounts= NewAve
Ave= WeightedCounts/ Weight
If Count = Weight then AveragingComplete = 1
If Count = Weight then Display “Weighted Average” ‘lcd routine
If Count < Weight then Display “building average” ‘lcd routine

[HankMcSpank]

In a different application I used a "weighted Average" where no one sample could mangle the running average.
This is the regurgitated conversion to PBP:

I initialize the values and add new value to the stack and subtract off the old average, giving the new value 1/weight of effect

It must be cos I suck at maths, but I've read that a few times & it's not sinking in. Can I use an example here to how that works in practise. Let's say six AtoD Samples are taken....

100
99
100
101
499
100

You said that your weighted average stops a spurious reading skewing the overall average...can you illustrate using those six samples how the 499 would be ignored?

Many thanks!