Add setArrays() function because of issue #32. Add API migration info to README and improve README.

README.md

@@ -4,7 +4,7 @@ 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.  
+~~This is a C++ library for Arduino for computing FFT.~~ Now it works both on Arduino and C projects. This is version 2.0 of the library, which has a different [API](#api). See here [how to migrate from 1.x to 2.x](#migrating-from-1.x-to-2.x).
 Tested on Arduino 1.6.11 and 1.8.10.
 
 ## Installation on Arduino
@@ -16,49 +16,57 @@ Use the Arduino Library Manager to install and keep it updated. Just look for ar
 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\src\arduinoFTT.h` (the library header file. include this in your project)  
 `Arduino\libraries\arduinoFTT\keywords.txt` (the syntax coloring file)  
-`Arduino\libraries\arduinoFTT\examples` (the examples in the "open" menu)  
+`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.
-
+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);  
+* ```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.
+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. You can deallocate `vReal` and `vImag` after you are done using the library, or only use specific library functions that only need one of those arrays.
 
-* **~ArduinoFFT**(void);  
+```C++
+const uint32_t nrOfSamples = 1024;
+auto real = new float[nrOfSamples];
+auto imag = new float[nrOfSamples];
+auto fft = ArduinoFFT<float>(real, imag, nrOfSamples, 10000);
+// ... fill real + imag and use it ...
+fft.compute();
+fft.complexToMagnitude();
+delete [] imag;
+// ... continue using real and only functions that use real ...
+auto peak = fft.majorPeak();
+```
+* ```~ArduinoFFT()```   
 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**();  
+* ```void complexToMagnitude() const;```  
+Convert complex values to their magnitude and store in vReal. Uses vReal and vImag.
+* ```void compute(FFTDirection dir) const;```  
+Calcuates the Fast Fourier Transform. Uses vReal and vImag.
+* ```void dcRemoval() const;```  
+Removes the DC component from the sample data. Uses vReal.
+* ```T majorPeak() const;```  
+Returns the frequency of the biggest spike in the analyzed signal. Uses vReal.
+* ```void majorPeak(T &frequency, T &value) const;```  
+Returns the frequency and the value of the biggest spike in the analyzed signal. Uses vReal.
+* ```uint8_t revision() const;```  
 Returns the library revision.
-* **windowing**(FFTWindow windowType, FFTDirection dir, bool withCompensation = false);  
-Performs a windowing function on the values array. The possible windowing options are:
+* ```void setArrays(T *vReal, T *vImag);```  
+Replace the data array pointers.
+* ```void windowing(FFTWindow windowType, FFTDirection dir, bool withCompensation = false);```  
+Performs a windowing function on the values array. Uses vReal. The possible windowing options are:
   * Rectangle
   * Hamming
   * Hann
@@ -91,3 +99,31 @@ Define this to use reciprocal multiplication for division and some more speedups
 
 * #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`.
+
+See the `FFT_speedup.ino` example in `Examples/FFT_speedup/FFT_speedup.ino`.
+
+# Migrating from 1.x to 2.x
+
+* The function signatures where you could pass in pointers were deprecated and have been removed. Pass in pointers to your real / imaginary array in the ArduinoFFT() constructor. If you have the need to replace those pointers during usage of the library (e.g. to free memory) you can do the following:
+
+```C++
+const uint32_t nrOfSamples = 1024;
+auto real = new float[nrOfSamples];
+auto imag = new float[nrOfSamples];
+auto fft = ArduinoFFT<float>(real, imag, nrOfSamples, 10000);
+// ... fill real + imag and use it ...
+fft.compute();
+fft.complexToMagnitude();
+delete [] real;
+// ... replace vReal in library with imag ...
+fft.setArrays(imag, nullptr);
+// ... keep doin whatever ...
+```
+* All function names are camelCase case now (start with lower-case character), e.g. "windowing()" instead of "Windowing()".
+
+## TODO
+* Ratio table for windowing function.
+* Document windowing functions advantages and disadvantages.
+* Optimize usage and arguments.
+* Add new windowing functions.
+* ~~Spectrum table?~~

changeLog.txt

@@ -1,8 +1,13 @@
+02/22/20 v1.9.1
+Add setArrays() function because of issue #32.
+Add API migration info to README and improve README.
+Use better sqrtf() approximation.
+
 02/19/20 v1.9.0
 Remove deprecated API. Consistent renaming of functions to lowercase.
 Make template to be able to use float or double type (float brings a ~70% speed increase on ESP32).
 Add option to provide cache for window function weighing factors (~50% speed increase on ESP32).
-Add some #defines to enable math approximisations to further speed up code (~50% speed increase on ESP32).
+Add some #defines to enable math approximisations to further speed up code (~40% speed increase on ESP32).
 
 01/27/20 v1.5.5
 Lookup table for constants c1 and c2 used during FFT comupting. This increases the FFT computing speed in around 5%.

keywords.txt

@@ -21,6 +21,7 @@ windowing	KEYWORD2
 exponent	KEYWORD2
 revision	KEYWORD2
 majorPeak	KEYWORD2
+setArrays	KEYWORD2
 
 #######################################
 # Constants (LITERAL1)

library.json

@@ -25,7 +25,7 @@
       "email": "bim.overbohm@googlemail.com"
     }
   ],
-  "version": "1.9.0",
+  "version": "1.9.1",
   "frameworks": ["arduino","mbed","espidf"],
   "platforms": "*"
 }

library.properties

@@ -1,5 +1,5 @@
 name=arduinoFFT
-version=1.9.0
+version=1.9.1
 author=Enrique Condes <enrique@shapeoko.com>
 maintainer=Enrique Condes <enrique@shapeoko.com>
 sentence=A library for implementing floating point Fast Fourier Transform calculations on Arduino.

src/arduinoFFT.h

@@ -106,6 +106,13 @@ public:
 		return 0x19;
 	}
 
+	// Replace the data array pointers
+	void setArrays(T *vReal, T *vImag)
+	{
+		_vReal = vReal;
+		_vImag = vImag;
+	}
+
 	// Computes in-place complex-to-complex FFT
 	void compute(FFTDirection dir) const
 	{
@@ -347,7 +354,7 @@ public:
 		return interpolatedX;
 	}
 
-	void majorPeak(T &f, T &v) const
+	void majorPeak(T &frequency, T &value) const
 	{
 		T maxY = 0;
 		uint_fast16_t IndexOfMaxY = 0;
@@ -372,8 +379,8 @@ public:
 			interpolatedX = ((IndexOfMaxY + delta) * this->_samplingFrequency) / (this->_samples);
 		}
 		// returned value: interpolated frequency peak apex
-		f = interpolatedX;
-		v = abs(this->_vReal[IndexOfMaxY - 1] - (2.0 * this->_vReal[IndexOfMaxY]) + this->_vReal[IndexOfMaxY + 1]);
+		frequency = interpolatedX;
+		value = abs(this->_vReal[IndexOfMaxY - 1] - (2.0 * this->_vReal[IndexOfMaxY]) + this->_vReal[IndexOfMaxY + 1]);
 	}
 
 private: