New software filter for adc reading

[Darrel Taylor]

Well no.

The sorting routine was OK.
It needs that statement because the sorting uses Raw_Data[Index + 1]
If you make your suggested change, it will overrun the array.

The problem is in the sampling portion.

If Index < sample then goto Read_Again

Should be ...

If Index <= sample then goto Read_Again
____________________ _______________________ ____________________

Ioannis: Thanks!

If you have a particular running average routine (I've seen several), I can throw it in the test.

And the data was formatted like this ... using a total of 300 samples

Ready
2.502, 2.534, 2.497, 2.497, 2.500
2.507, 2.529, 2.497, 2.497, 2.500
2.487, 2.529, 2.492, 2.497, 2.500
2.502, 2.534, 2.502, 2.502, 2.500
2.502, 2.534, 2.502, 2.502, 2.500
2.507, 2.529, 2.492, 2.492, 2.500
2.517, 2.529, 2.497, 2.497, 2.500
2.492, 2.529, 2.497, 2.497, 2.500
2.492, 2.534, 2.502, 2.502, 2.500
2.507, 2.534, 2.502, 2.502, 2.500
2.517, 2.529, 2.497, 2.497, 2.500
2.497, 2.529, 2.492, 2.497, 2.500
2.502, 2.529, 2.497, 2.497, 2.500
2.512, 2.534, 2.497, 2.497, 2.500
2.497, 2.534, 2.502, 2.502, 2.500

The order is ... Raw, Median, Melanie, Average, Oversample.

I cut&paste the data from the terminal program into Excel and used the "Text to Columns" command.

We could create another thread and test out various averaging routines.
Figure out the best sample size and measurement techniques. But I doubt anything could ever be better than Oversampling.

[Ioannis]

Hi Darrel.I too agree that nothing may beat the oversampling. It is obvious.

The average I have in mind would be average=average*15/16+sample. Not many, but not too little and /16 can be done fast with shifts.

Cut and paste? Well, I was thinking too complex I guess...

Ioannis

[Jerson]

The average I have in mind would be average=average*15/16+sample. Not many, but not too little and /16 can be done fast with shifts.
Ioannis

Ioannis, I think you must have meant

Average = (Average*15 + sample)/16

[Ioannis]

Yes Jerson. That was it. It was too late here, so...

Thanks for correcting.

Ioannis

[aratti]

Darrel thank you for pointing out where the error was. So obvious that I could not see it!

I have an improvment (mark2) and I will be glad to post it, if you could test it under the same condition as for mark1.

I am asking that since you have suggested to create another thread for testing the various statistical manipolation of the raw data. So please let me know if you are going to create this thread or if I can post it here.

Thank you again for your work.

Cheers

Al.

[Darrel Taylor]

Sure, post it here. This thread is about your routines.

My stuff is at the office, so I'll run it and the moving average Monday (if I don't get snowed in).

I'm still thinking about starting the other thread, but it needs to use a bigger chip, have different noise types and frequencies, use pre-sampled datasets so they're each working with the same samples, maybe some software and circuits to automate the process, etc. .... it may be awhile.

[Charlie]

Ioannis, I think you must have meant

Average = (Average*15 + sample)/16

One of the issues with so many samples is that you may run into the maximum size of numbers. You may need to play with the order of operations or break it into several steps to make sure you don't accidentally wrap. You also likely will be dropping significant digits which may or may not be an issue.

[aratti]

Hi Darrel here the version 2. In this version, I am using the mean instead of single data and then I select the median. Let see how it perform.

Charlie:

With a 12 bits ADC there is the possibility of overflow, with a 10 bits ADC you are ways within the word size, even if you sample 1023 which is the maximum value.

Cheers

Al.

[Darrel Taylor]

Sorry for the delay, I was getting unexpected results from the moving average and I wanted to make sure it wasn't something I was doing wrong.
But I 'll get to that in a minute.

Al, here's the results of "Mark2" under the same conditions as before.
I haven't changed the voltage calculation for it, so it's still reading higher than normal.
It looks a little different, but still jumps +/- 2 counts fairly frequently.



Now notice the green line in the above plot.
What, you don't see it ... me neither.
It turns out that the Running average is so slow to respond that it's reading is not even on the chart.
Zooming out a bit shows this ...



This was the formula used ...

RunAverage  VAR WORD

ADCIN  0, ADval
RunAverage = (RunAverage*15 + ADval)/16

I let it run for over an hour and it was getting close, but it still hadn't reached 2.5 volts.
I don't think I'd want to use that formula.

[Ioannis]

Thanks Darrel. Is that on the X-axis ... time? I guess it is and the time it takes is forever.

OK, if we use 3/4 will sure be faster, but how accurate?

On an experiment with touch sensors I can confirm that it could not get close to the real sample value though...

Ioannis