2 channel filter

Projects Programming
1

Hi
Why on serial plotter both Af and Bf are the same ?

#include <filters.h>

const float cutoff_freq   = 5.0;  //Cutoff frequency in Hz
const float sampling_time = 0.005; //Sampling time in seconds.
IIR::ORDER  order  = IIR::ORDER::OD3; // Order (OD1 to OD4)

// Low-pass filter
Filter f(cutoff_freq, sampling_time, order);

void setup() {
  Serial.begin(115200);
}

void loop() {
  int valueA = analogRead(PA5);//+++++++++++++++++++++++++++++++++++++++++
  float filteredvalA = f.filterIn(valueA);
  int valueB = analogRead(PA7);  //+++++++++++++++++++++++++++++++++++++++
  float filteredvalB = f.filterIn(valueB);
  Serial.print("A = ");
  //Serial.print(valueA, DEC);
  Serial.print("  Af = ");
  Serial.print(filteredvalA, 4);

  Serial.print("  B =  ");
 // Serial.print(valueB , DEC);
  Serial.print("  Bf =  ");
  Serial.println(filteredvalB , 4);
  delay(5); // Loop time will approx. match the sampling time.
}
2

Perhaps because valueA and valueB are the same?

Did you run the examples coming with the library?

Try two Filter fA, fB for separate signals A and B.

3

Thanks
Problem solved

4

For the records: How that?

5 
#include <filters.h>

const float cutoff_freqA   = 5.0;  //Cutoff frequency in Hz
const float sampling_timeA = 0.005; //Sampling time in seconds.
IIR::ORDER  orderA  = IIR::ORDER::OD3; // Order (OD1 to OD4)
///////////////////
const float cutoff_freqB   = 5.0;  //Cutoff frequency in Hz
const float sampling_timeB = 0.005; //Sampling time in seconds.
IIR::ORDER  orderB  = IIR::ORDER::OD3; // Order (OD1 to OD4)
//////////////////
// Low-pass filter
Filter fA(cutoff_freqA, sampling_timeA, orderA);
Filter fB(cutoff_freqB, sampling_timeB, orderB);
void setup() {
  Serial.begin(115200);
}

void loop() {
  int valueA = analogRead(PA5);//+++++++++++++++++++++++++++++++++++++++++
  float filteredvalA = fA.filterIn(valueA);
  int valueB = analogRead(PA7);  //+++++++++++++++++++++++++++++++++++++++
  float filteredvalB = fB.filterIn(valueB);
  // Serial.print("A = ");
  // Serial.print(valueA, DEC);
  Serial.print("  Af = ");
  Serial.print(filteredvalA, 4);

  //  Serial.print("  B =  ");
  // Serial.print(valueB , DEC);
  Serial.print("  Bf =  ");
  Serial.println(filteredvalB , 4);
  delay(5); // Loop time will approx. match the sampling time.
}
1 Like
6

Please post a link to the filter library you are using.

7

https://github.com/MartinBloedorn/libFilter/blob/master/filters.h

8

Thanks! Documentation is pretty weak but if it does what you want, fine.

9

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