A lightweight C++ library for digital filter synthesis on embedded environments, with support for runtime design adjustments.
This library aims to provide a flexible and efficient way to implement classical IIR filters such as Butterworth and Chebyshev directly on microcontrollers and other resource-constrained devices.

Below is the response graph generated by the filters implemented in this library:

• Frequency: 2000 Hz
• Lowcut frequency: 300 Hz
• Highcut frequency: 600 Hz
• Chebyshev I ripple: 1 dB
• Chebyshev II ripple: 30 dB

• Runtime-adjustable cutoff frequencies and sampling rates
• Biquad section generation for efficient runtime filtering
• Header-only, portable, and STL-compatible (optional)
• Stack-based memory allocation for improved performance and readability on systems with limited volatile memory

Just include the header files in your project and call for the tools inside FilterDesigner namespace.

Below is a example of how to use the library in a C++ project:

//Include the Butterworth designer
#include "butterworth_design.hpp"

//Only bandpass filter
using FilterDesigner::ButterworthBandpass;

//Filter parameters
const float g_samples = 200.0;  //Sample rate frequency [Hz]
const float g_lowcut  = 15.0;   //Low cut frequency     [Hz]
const float g_highcut = 25.0;   //High cut frequency    [Hz]
const short g_order   = 4;      //Filter order

//Create a Butterworth band-pass design.
ButterworthBandpass<float, g_order> filter(g_samples, g_lowcut, g_highcut);

//Checks if filter synthesis fail
if (!filter.designSuccess()) while (true) { }

//= LOOP ================================================================== 
//Sinusoidal signals
float s1 = sin(1.0 * PI * 10.0 * interval_micros);  //10 Hz
float s2 = sin(1.0 * PI * 20.0 * interval_micros);  //20 Hz
float s3 = sin(1.0 * PI * 30.0 * interval_micros);  //30 Hz

//Merge signals
float input = s1 + s2 + s3;

//​Generates the output signal using a raw signal through biquad cascade.
float output = input;
for (size_t index = 0; index < filter.m_num_biquads; index++)
      output = filter.m_biquads[index].process(output);

• Fix odd order filter generation
• Add support for arbitrary band-stop filters
• Add Elliptic filter designs
• Add CMSIS support for ARM architecture
• Include fixed-point arithmetic mode for deeply embedded systems