https://github.com/tttapa/arduino-filters

Arduino Finite Impulse Response and Infinite Impulse Response filter implementations.
https://github.com/tttapa/arduino-filters

Last synced: about 1 month ago
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Arduino Finite Impulse Response and Infinite Impulse Response filter implementations.

• Host: GitHub
• URL: https://github.com/tttapa/arduino-filters
• Owner: tttapa
• License: gpl-3.0
• Created: 2019-11-11T16:31:33.000Z (about 5 years ago)
• Default Branch: master
• Last Pushed: 2022-05-19T04:12:36.000Z (over 2 years ago)
• Last Synced: 2024-03-16T11:42:22.266Z (9 months ago)
• Language: C++
• Size: 20.4 MB
• Stars: 107
• Watchers: 8
• Forks: 14
• Open Issues: 7
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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# Arduino Filters

## Features

- **Infinite Impulse Response Filters**

- **Finite Impulse Response Filters**

- **BiQuad Filters**

- **Butterworth Filters**

- **Notch Filters**

- **Median Filters**

- **Simple and Exponential Moving Average Filters**

- **Hysteresis**

These filters were originally part of the

[old Filters library](https://github.com/tttapa/Filters).  

It has been updated completely, with continuous integration, unit tests, etc.

## Documentation

The automatically generated Doxygen documentation for this library can be found 

here:  

[**Documentation**](https://tttapa.github.io/Arduino-Filters/Doxygen/index.html)  

Test coverage information can be found here:  

[**Code Coverage**](https://tttapa.github.io/Arduino-Filters/Coverage/index.html)  

Arduino examples can be found here:  

[**Examples**](https://tttapa.github.io/Arduino-Filters/Doxygen/examples.html)

You might want to start with the 

[**Filters Module**](https://tttapa.github.io/Arduino-Filters/Doxygen/d2/d5a/group__Filters.html).

## Example: Butterworth filter

```cpp

#include 

#include 

#include 

void setup() {

  Serial.begin(115200);

}

// Sampling frequency

const double f_s = 100; // Hz

// Cut-off frequency (-3 dB)

const double f_c = 40; // Hz

// Normalized cut-off frequency

const double f_n = 2 * f_c / f_s;

// Sample timer

Timer 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)));

}

```

## Tools

The [`python`](python) folder contains some Python scripts to visualize the

frequency response of the filters used in the examples.  

### Butterworth Filter

![Butterworth.ino](python/butterworth.svg)

### FIR Notch Filter

![FIRNotch.ino](python/firnotch.svg)

## Related Projects

This library uses the

[**Arduino Helpers utility library**](https://github.com/tttapa/Arduino-Helpers)

## Supported boards

For each commit, the continuous integration tests compile the examples for the

following boards:

- Arduino UNO

- Arduino Mega

- Arduino Leonardo

- Teensy 3.2

- Teensy 4.1

- Arduino Due

- Arduino Nano 33 IoT

- Arduino Nano 33 BLE

- Arduino Nano Every

- ESP8266

- ESP32

This covers a very large part of the Arduino platform, and similar boards will

also work (e.g. Arduino Nano, Arduino Mega, etc.).

If you have a board that's not supported, please 

[open an issue](https://github.com/tttapa/Arduino-Helpers/issues/new)

and let me know!

### Known limitations

The Arduino Due toolchain provided by Arduino is very old, and has some 

configuration problems. As a result, some math functions are not available.  

There is nothing I can do about it in this library, it's a bug in the Arduino 

Due Core.