git.piffa.net Git - arduino/blob - books/ArduinoNextSteps-master/ArduinoNextSteps/filter_test/filter_test.ino

   1
   2
   3 // 300 to 3000 band stop filter
   4 // 100 kHz sample rate
   5 // http://www.schwietering.com/jayduino/filtuino/index.php?characteristic=bu&passmode=bs&order=2&usesr=usesr&sr=100000&frequencyLow=300&noteLow=&frequencyHigh=3000&noteHigh=&pw=pw&calctype=float&run=Send
   6
   7 //Band stop butterworth filter order=2 alpha1=0.003 alpha2=0.03
   8 class filter
   9 {
  10         public:
  11                 filter()
  12                 {
  13                         for(int i=0; i <= 4; i++)
  14                                 v[i]=0.0;
  15                 }
  16         private:
  17                 float v[5];
  18         public:
  19                 float step(float x)
  20                 {
  21                         v[0] = v[1];
  22                         v[1] = v[2];
  23                         v[2] = v[3];
  24                         v[3] = v[4];
  25                         v[4] = (8.869368704884e-1 * x)
  26                                  + ( -0.7866981284 * v[0])
  27                                  + (  3.3285093824 * v[1])
  28                                  + ( -5.2961761521 * v[2])
  29                                  + (  3.7543536539 * v[3]);
  30                         return
  31                                  1.000000 * v[0]
  32                                 +v[4]
  33                                 - 3.992879 * (v[1] + v[3])
  34                                 +5.985770 * v[2];
  35                 }
  36 };
  37
  38 filter f;
  39
  40 void setup()
  41 {
  42   Serial.begin(9600);
  43 }
  44
  45 void loop()
  46 {
  47   int r = analogRead(A0);
  48   float filtered = f.step(r);
  49   Serial.print(r); Serial.print(","); Serial.println((int)filtered);
  50   delay(100);
  51 }
  52
  53