Dealing with large numbers that exceed the 16-bit limit

Andy McLeod

I am sampling from a 12-bit ADC at 10Hz for 30 seconds per sample cycle. All I need is the mean value, the raw values are discarded. While summing these 300 12-bit numbers, I exceed the 16 bit limit of 65536 for the Stamp rather quickly. Does anyone have a routine that will allow me to do this?

Beau Schwabe

This works like a Digital LOW-PASS filter.· With a 12-bit input value you would effectively have a 16 sample averaging window.

Define Sample as a WORD····· <- This is your input variable
Define Average as a WORD···· <- This is your output variable
Define DataBase as a WORD
Define SampleNum as a CONstant (with 12-bits, the MAXIMUM this can be is 16 ; 65536 / 2^12 = 16 )



Main Program Loop:

{ Update Sample here }
DataBase = DataBase - Average + Sample
Average = DataBase / SampleNum
{ Read Average Here }

return to 'Main Program Loop'






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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Chris Savage

Andy,
·
·· Also check the following link from Dr. Tracy Allen’s website.· He has some interesting math routines on there as well as a wealth of other useful information.· Take care.

http://www.emesys.com/BS2math6.htm

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Chris Savage
Parallax Tech Support

Bean

Andy,

If you voltage doesn't change too much, you could take an initial reading, then sum the DIFFERENCES between each sample and the initial reading. After all the samples are taken, divide the sum of difference by the number of samples and add to the initial reading.

Bean.

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