arduinoFFT

Fast Fourier Transform for Arduino

This is a fork from https://code.google.com/p/makefurt/ which has been abandoned since 2011. This is a C++ library for Arduino for computing FFT. Now it works both on Arduino and C projects.
Tested on Arduino 1.6.11 and 1.8.10.

Installation on Arduino

Use the Arduino Library Manager to install and keep it updated. Just look for arduinoFFT. Only for Arduino 1.5+

Manual installation on Arduino

To install this library, just place this entire folder as a subfolder in your Arduino installation. When installed, this library should look like:

Arduino\libraries\arduinoFTT (this library's folder)
Arduino\libraries\arduinoFTT\arduinoFTT.h (the library header file, uses 32 bit floats or 64bit doubles)
Arduino\libraries\arduinoFTT\keywords.txt (the syntax coloring file)
Arduino\libraries\arduinoFTT\examples (the examples in the "open" menu)
Arduino\libraries\arduinoFTT\LICENSE (GPL license file)
Arduino\libraries\arduinoFTT\README.md (this file)

Building on Arduino

After this library is installed, you just have to start the Arduino application. You may see a few warning messages as it's built.

To use this library in a sketch, go to the Sketch | Import Library menu and select arduinoFTT. This will add a corresponding line to the top of your sketch:

#include <arduinoFTT.h>

TODO

• Ratio table for windowing function.
• Document windowing functions advantages and disadvantages.
• Optimize usage and arguments.
• Add new windowing functions.
• Spectrum table?

API

• ArduinoFFT(T *vReal, T *vImag, uint_fast16_t samples, T samplingFrequency, T * weighingFactors = nullptr);
  Constructor. The type T can be float or double. vReal and vImag are pointers to arrays of real and imaginary data and have to be allocated outside of ArduinoFFT. samples is the number of samples in vReal and vImag and weighingFactors (if specified). samplingFrequency is the sample frequency of the data. weighingFactors can optionally be specified to cache weighing factors for the windowing function. This speeds up repeated calls to windowing() significantly.

• ~ArduinoFFT(void);
  Destructor.

• complexToMagnitude();
  Convert complex values to their magnitude and store in vReal.

• compute(FFTDirection dir);
  Calcuates the Fast Fourier Transform.

• dcRemoval();
  Removes the DC component from the sample data.

• majorPeak();
  Looks for and returns the frequency of the biggest spike in the analyzed signal.

• revision();
  Returns the library revision.

• windowing(FFTWindow windowType, FFTDirection dir);
  Performs a windowing function on the values array. The possible windowing options are:

  • Rectangle
  • Hamming
  • Hann
  • Triangle
  • Nuttall
  • Blackman
  • Blackman_Nuttall
  • Blackman_Harris
  • Flat_top
  • Welch

Special flags

You can define these before including arduinoFFT.h:

• #define FFT_SPEED_OVER_PRECISION
  Define this to use reciprocal multiplication for division and some more speedups that might decrease precision.

• #define FFT_SQRT_APPROXIMATION
  Define this to use a low-precision square root approximation instead of the regular sqrt() call. This might only work for specific use cases, but is significantly faster. Only works if T == float.