adis300 / filter-c

Elegant Butterworth and Chebyshev filter implemented in C, with float/double precision support. Works well on many platforms. You can also use this package in C++ and bridge to many other languages for good performance.

filter-c

Elegant Butterworth and Chebyshev filter implemented in C, with float/double precision support. Works well on many platforms. You can also use this package in C++ and bridge to many other languages for good performance.

Features

• lowpass
• highpass
• bandpass
• bandstop

This imlementation is based on algorithm from https://exstrom.com/journal/sigproc/dsigproc.html

Run example

make example
./example

Steps to use a filter

1. Create a filter object using create_***_pass/stop(params...)

2. Use filter to filter incoming numbers one by one. The output is a double or float that can be specified in header.

3. After using the filter, release the filter using free_***_pass/stop(filter).

filter-c's Issues

First order filters question

Hi, is there a simple way, create a first-order filter using your code?

Cutoff frequency set directly

Hello, s/f as normalized frequency. When I set the sampling frequency to 250HZ according to the example, and set f to 3hz, I cannot get the ideal result using a simple sine wave test. I would like to ask how to conveniently set the cutoff frequency?

thanks

The high-pass filter oscillates.

After I use a 0.5Hz high-pass filter, small signals will turn into sawtooth waves. However, if I use a 10Hz low-pass filter, there is no problem.
I use arduino external ADC and use this filter
HPF:
BWHighPass* filter = create_bw_high_pass_filter(3, 400, 0.5);
Serial.println(bw_high_pass(filter,adcv[2]),6);

LPF:
BWLowPass* filter = create_bw_low_pass_filter(3, 400, 10);
Serial.println(bw_low_pass(filter,adcv[2]),6);

Chebyshev filter type?

Thanks for your work!
I wanted to know whether the Chebyshev bandpass filter implementation is type I or type II?