Any good way for analogRead readings calibration?

[espruino-discuss3]

Posted at 2016-12-11 by bigplik

hi, I want to write code for analogReads sampling, in C i use for loop, I want to make let say 50-100 reads before I print them to console or to display, then can make analogRead a bit more precise as the readings floats a bit when use just simple analogRead function and timer Interval,
I appreciate some advice in this case

[espruino-discuss3]

Posted at 2016-12-11 by @MaBecker

Hi @bigplik

which device are you using ?

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Posted at 2016-12-11 by bigplik

hi @MaBecker I use Pico this time

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Posted at 2016-12-11 by @MaBecker

ok - use search to find all conversation on this topic like this

http://forum.espruino.com/search/?q=analog+type:conversation+inTitle:true+sort:date

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Posted at 2016-12-11 by @MaBecker

let us know which topic was helpful :-)

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Posted at 2016-12-12 by @gfwilliams

I guess the easiest is just:

function analogReadAvr(p) {
  var n=0,i=100;
  while (i--) n+=analogRead(p);
  return n/100;
}

But you can do other things - for example reading in the background using Waveform, and/or using .sort to do median filtering.

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Posted at 2018-08-11 by @MaBecker

Thanks for naming the median filtering technic, using this now for several devices running Espruino. Works fine for me with sampleCount = 21.

analogReadMedian = function(p, sampleCount) {
      var samples = Math.floor(sampleCount);
      var analogValues = new Array(samples);
      // read analog values into array
      i = samples;
      while(i--) analogValues[i] = analogRead(p);
      //sort array, smalest first and largest last
      analogValues.sort(function(a, b){return a-b;});
      // set median
      i = Math.floor(samples/2);
      if ( samples % 2 ){ //even
          median = (analogValues[i]+analogValues[i+1])/2;
      } else { // odd
          median = analogValues[i];
      }
      return median;
};

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Posted at 2018-08-11 by @allObjects

Declaring / Initializing i and median in the function var i, median; would be a healthy thing... otherwise some things may get messed up...

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Posted at 2018-08-12 by @MaBecker

Thanks, so this will ensure that not messing up global vars with the same name.

analogReadMedian = function(p, sampleCount) {
      var i, median;
      var samples = Math.floor(sampleCount);
      var analogValues = new Array(samples);
      // read analog values into array
      i = samples;
      while(i--) analogValues[i] = analogRead(p);
      //sort array, smalest first and largest last
      analogValues.sort(function(a, b){return a-b;});
      // set median
      i = Math.floor(samples/2);
      if ( samples % 2 ){ //even
          median = (analogValues[i]+analogValues[i+1])/2;
      } else { // odd
          median = analogValues[i];
      }
      return median;
};