Butterworth.ino

Butterworth

Example of Butterworth filter.

Boards:

AVR, AVR USB, Nano 33 IoT, Nano 33 BLE, Due, Teensy 3.x, ESP8266, ESP32

See also

https://tttapa.github.io/Pages/Mathematics/Systems-and-Control-Theory/Analog-Filters/Butterworth-Filters.html

Written by PieterP, 2019-11-12
https://github.com/tttapa/Arduino-Filters

 
#include <Filters.h>
 
#include <AH/Timing/MillisMicrosTimer.hpp>
#include <Filters/Butterworth.hpp>
 
void setup() {
  Serial.begin(115200);
}
 
// Sampling frequency
const double f_s = 100; // Hz
// Cut-off frequency (-3 dB)
const double f_c = 25; // Hz
// Normalized cut-off frequency
const double f_n = 2 * f_c / f_s;
 
// Sample timer
Timer<micros> timer = std::round(1e6 / f_s);
 
// Sixth-order Butterworth filter
auto filter = butter<6>(f_n);
 
void loop() {
  if (timer)
    Serial.println(filter(analogRead(A0)));
}