Version 1.4

- Descriptor for Plaformio
- New API with simpled functions
- Fixes on rare bugs

README.md

@@ -11,6 +11,10 @@ Tested on Arduino 1.6.11
 
 ### 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:
@@ -37,23 +41,28 @@ select arduinoFTT.  This will add a corresponding line to the top of your sketch
 * Document windowing functions advantages and disadvantages.
 * Optimize usage and arguments.
 * Add new windowing functions.
-* Spectrum table?
+<del>* Spectrum table? </del>
 
 ### API
 
 * **arduinoFFT**(void);
+* **arduinoFFT**(double *vReal, double *vImag, uint16_t samples, double samplingFrequency);
 Constructor
 * **~arduinoFFT**(void);
 Destructor
 * **ComplexToMagnitude**(double *vReal, double *vImag, uint16_t samples);
+* **ComplexToMagnitude**();
 * **Compute**(double *vReal, double *vImag, uint16_t samples, uint8_t dir);
-Calculates the power value according to **Exponent** and calcuates the Fast Fourier Transform.
 * **Compute**(double *vReal, double *vImag, uint16_t samples, uint8_t power, uint8_t dir);
+* **Compute**(uint8_t dir);
 Calcuates the Fast Fourier Transform.
 * **MajorPeak**(double *vD, uint16_t samples, double samplingFrequency);
+* **MajorPeak**();
+Looks for and returns the frequency of the biggest spike in the analyzed signal.
 * **Revision**(void);
 Returns the library revision.
 * **Windowing**(double *vData, uint16_t samples, uint8_t windowType, uint8_t dir);
+* **Windowing**(uint8_t windowType, uint8_t dir);
 Performs a windowing function on the values array. The possible windowing options are:
     * FFT_WIN_TYP_RECTANGLE
     * FFT_WIN_TYP_HAMMING

changeLog.txt

@@ -1,3 +1,9 @@
+02/10/18 v1.4
+Transition version. Minor optimization to functions. New API. Deprecation of old functions.
+
+12/06/18 v1.3
+Add support for mbed development boards.
+
 09/04/17 v1.2.3
 Finally solves the issue of Arduino IDE not correctly detecting and highlighting the keywords.
 

library.json

@@ -0,0 +1,26 @@
+{
+  "name": "arduinoFFT",
+  "keywords": "FFT, Fourier, FDT, frequency",
+  "description": "A library for implementing floating point Fast Fourier Transform calculations.",
+  "repository":
+  {
+    "type": "git",
+    "url": "https://github.com/kosme/arduinoFFT.git"
+  },
+  "authors":
+  [
+    {
+      "name": "Enrique Condes",
+      "email": "enrique@shapeoko.com",
+      "maintainer": true
+    },
+    {
+      "name": "Didier Longueville",
+      "url": "http://www.arduinoos.com/",
+      "email": "contact@arduinoos.com"
+    }
+  ],
+  "version": "1.4",
+  "frameworks": ["arduino","mbed","espidf"],
+  "platforms": "*"
+}

library.properties

@@ -1,6 +1,6 @@
 name=arduinoFFT
-version=1.3
+version=1.4
-author=kosme <enrique@shapeoko.com>
+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.
 paragraph=With this library you can calculate the frequency of a sampled signal.

src/arduinoFFT.cpp

@@ -22,13 +22,22 @@
 #include "arduinoFFT.h"
 
 arduinoFFT::arduinoFFT(void)
-{
+{ // Constructor
-/* Constructor */
+	#warning("This method is deprecated and will be removed on future revisions.")
+}
+
+arduinoFFT::arduinoFFT(double *vReal, double *vImag, uint16_t samples, double samplingFrequency)
+{// Constructor
+	this->_vReal = vReal;
+	this->_vImag = vImag;
+	this->_samples = samples;
+	this->_samplingFrequency = samplingFrequency;
+	this->_power = Exponent(samples);
 }
 
 arduinoFFT::~arduinoFFT(void)
 {
-/* Destructor */
+// Destructor
 }
 
 uint8_t arduinoFFT::Revision(void)
@@ -38,18 +47,75 @@ uint8_t arduinoFFT::Revision(void)
 
 void arduinoFFT::Compute(double *vReal, double *vImag, uint16_t samples, uint8_t dir)
 {
+	#warning("This method is deprecated and will be removed on future revisions.")
 	Compute(vReal, vImag, samples, Exponent(samples), dir);
 }
 
+void arduinoFFT::Compute(uint8_t dir)
+{// Computes in-place complex-to-complex FFT /
+	// Reverse bits /
+	uint16_t j = 0;
+	for (uint16_t i = 0; i < (this->_samples - 1); i++) {
+		if (i < j) {
+			Swap(&this->_vReal[i], &this->_vReal[j]);
+			if(dir==FFT_REVERSE)
+				Swap(&this->_vImag[i], &this->_vImag[j]);
+		}
+		uint16_t k = (this->_samples >> 1);
+		while (k <= j) {
+			j -= k;
+			k >>= 1;
+		}
+		j += k;
+	}
+	// Compute the FFT  /
+	double c1 = -1.0;
+	double c2 = 0.0;
+	uint16_t l2 = 1;
+	for (uint8_t l = 0; (l < this->_power); l++) {
+		uint16_t l1 = l2;
+		l2 <<= 1;
+		double u1 = 1.0;
+		double u2 = 0.0;
+		for (j = 0; j < l1; j++) {
+			 for (uint16_t i = j; i < this->_samples; i += l2) {
+					uint16_t i1 = i + l1;
+					double t1 = u1 * this->_vReal[i1] - u2 * this->_vImag[i1];
+					double t2 = u1 * this->_vImag[i1] + u2 * this->_vReal[i1];
+					this->_vReal[i1] = this->_vReal[i] - t1;
+					this->_vImag[i1] = this->_vImag[i] - t2;
+					this->_vReal[i] += t1;
+					this->_vImag[i] += t2;
+			 }
+			 double z = ((u1 * c1) - (u2 * c2));
+			 u2 = ((u1 * c2) + (u2 * c1));
+			 u1 = z;
+		}
+		c2 = sqrt((1.0 - c1) / 2.0);
+		if (dir == FFT_FORWARD) {
+			c2 = -c2;
+		}
+		c1 = sqrt((1.0 + c1) / 2.0);
+	}
+	// Scaling for reverse transform /
+	if (dir != FFT_FORWARD) {
+		for (uint16_t i = 0; i < this->_samples; i++) {
+			 this->_vReal[i] /= this->_samples;
+			 this->_vImag[i] /= this->_samples;
+		}
+	}
+}
+
 void arduinoFFT::Compute(double *vReal, double *vImag, uint16_t samples, uint8_t power, uint8_t dir)
-{
+{	// Computes in-place complex-to-complex FFT
-/* Computes in-place complex-to-complex FFT */
+	// Reverse bits
-	/* Reverse bits */
+	#warning("This method is deprecated and will be removed on future revisions.")
 	uint16_t j = 0;
 	for (uint16_t i = 0; i < (samples - 1); i++) {
 		if (i < j) {
 			Swap(&vReal[i], &vReal[j]);
-			Swap(&vImag[i], &vImag[j]);
+			if(dir==FFT_REVERSE)
+				Swap(&vImag[i], &vImag[j]);
 		}
 		uint16_t k = (samples >> 1);
 		while (k <= j) {
@@ -58,7 +124,7 @@ void arduinoFFT::Compute(double *vReal, double *vImag, uint16_t samples, uint8_t
 		}
 		j += k;
 	}
-	/* Compute the FFT  */
+	// Compute the FFT
 	double c1 = -1.0;
 	double c2 = 0.0;
 	uint16_t l2 = 1;
@@ -87,7 +153,7 @@ void arduinoFFT::Compute(double *vReal, double *vImag, uint16_t samples, uint8_t
 		}
 		c1 = sqrt((1.0 + c1) / 2.0);
 	}
-	/* Scaling for reverse transform */
+	// Scaling for reverse transform
 	if (dir != FFT_FORWARD) {
 		for (uint16_t i = 0; i < samples; i++) {
 			 vReal[i] /= samples;
@@ -96,44 +162,95 @@ void arduinoFFT::Compute(double *vReal, double *vImag, uint16_t samples, uint8_t
 	}
 }
 
+void arduinoFFT::ComplexToMagnitude()
+{ // vM is half the size of vReal and vImag
+	for (uint16_t i = 0; i < this->_samples; i++) {
+		this->_vReal[i] = sqrt(sq(this->_vReal[i]) + sq(this->_vImag[i]));
+	}
+}
+
 void arduinoFFT::ComplexToMagnitude(double *vReal, double *vImag, uint16_t samples)
-{
+{	// vM is half the size of vReal and vImag
-/* vM is half the size of vReal and vImag */
+	#warning("This method is deprecated and will be removed on future revisions.")
 	for (uint16_t i = 0; i < samples; i++) {
 		vReal[i] = sqrt(sq(vReal[i]) + sq(vImag[i]));
 	}
 }
 
+void arduinoFFT::Windowing(uint8_t windowType, uint8_t dir)
+{// Weighing factors are computed once before multiple use of FFT
+// The weighing function is symetric; half the weighs are recorded
+	double samplesMinusOne = (double(this->_samples) - 1.0);
+	for (uint16_t i = 0; i < (this->_samples >> 1); i++) {
+		double indexMinusOne = double(i);
+		double ratio = (indexMinusOne / samplesMinusOne);
+		double weighingFactor = 1.0;
+		// Compute and record weighting factor
+		switch (windowType) {
+		case FFT_WIN_TYP_RECTANGLE: // rectangle (box car)
+			weighingFactor = 1.0;
+			break;
+		case FFT_WIN_TYP_HAMMING: // hamming
+			weighingFactor = 0.54 - (0.46 * cos(twoPi * ratio));
+			break;
+		case FFT_WIN_TYP_HANN: // hann
+			weighingFactor = 0.54 * (1.0 - cos(twoPi * ratio));
+			break;
+		case FFT_WIN_TYP_TRIANGLE: // triangle (Bartlett)
+			weighingFactor = 1.0 - ((2.0 * abs(indexMinusOne - (samplesMinusOne / 2.0))) / samplesMinusOne);
+			break;
+		case FFT_WIN_TYP_BLACKMAN: // blackmann
+			weighingFactor = 0.42323 - (0.49755 * (cos(twoPi * ratio))) + (0.07922 * (cos(fourPi * ratio)));
+			break;
+		case FFT_WIN_TYP_FLT_TOP: // flat top
+			weighingFactor = 0.2810639 - (0.5208972 * cos(twoPi * ratio)) + (0.1980399 * cos(fourPi * ratio));
+			break;
+		case FFT_WIN_TYP_WELCH: // welch
+			weighingFactor = 1.0 - sq((indexMinusOne - samplesMinusOne / 2.0) / (samplesMinusOne / 2.0));
+			break;
+		}
+		if (dir == FFT_FORWARD) {
+			this->_vReal[i] *= weighingFactor;
+			this->_vReal[this->_samples - (i + 1)] *= weighingFactor;
+		}
+		else {
+			this->_vReal[i] /= weighingFactor;
+			this->_vReal[this->_samples - (i + 1)] /= weighingFactor;
+		}
+	}
+}
+
+
 void arduinoFFT::Windowing(double *vData, uint16_t samples, uint8_t windowType, uint8_t dir)
-{
+{// Weighing factors are computed once before multiple use of FFT
-/* Weighing factors are computed once before multiple use of FFT */
+// The weighing function is symetric; half the weighs are recorded
-/* The weighing function is symetric; half the weighs are recorded */
+	#warning("This method is deprecated and will be removed on future revisions.")
 	double samplesMinusOne = (double(samples) - 1.0);
 	for (uint16_t i = 0; i < (samples >> 1); i++) {
 		double indexMinusOne = double(i);
 		double ratio = (indexMinusOne / samplesMinusOne);
 		double weighingFactor = 1.0;
-		/* Compute and record weighting factor */
+		// Compute and record weighting factor
 		switch (windowType) {
-		case FFT_WIN_TYP_RECTANGLE: /* rectangle (box car) */
+		case FFT_WIN_TYP_RECTANGLE: // rectangle (box car)
 			weighingFactor = 1.0;
 			break;
-		case FFT_WIN_TYP_HAMMING: /* hamming */
+		case FFT_WIN_TYP_HAMMING: // hamming
 			weighingFactor = 0.54 - (0.46 * cos(twoPi * ratio));
 			break;
-		case FFT_WIN_TYP_HANN: /* hann */
+		case FFT_WIN_TYP_HANN: // hann
 			weighingFactor = 0.54 * (1.0 - cos(twoPi * ratio));
 			break;
-		case FFT_WIN_TYP_TRIANGLE: /* triangle (Bartlett) */
+		case FFT_WIN_TYP_TRIANGLE: // triangle (Bartlett)
 			weighingFactor = 1.0 - ((2.0 * abs(indexMinusOne - (samplesMinusOne / 2.0))) / samplesMinusOne);
 			break;
-		case FFT_WIN_TYP_BLACKMAN: /* blackmann */
+		case FFT_WIN_TYP_BLACKMAN: // blackmann
 			weighingFactor = 0.42323 - (0.49755 * (cos(twoPi * ratio))) + (0.07922 * (cos(fourPi * ratio)));
 			break;
-		case FFT_WIN_TYP_FLT_TOP: /* flat top */
+		case FFT_WIN_TYP_FLT_TOP: // flat top
 			weighingFactor = 0.2810639 - (0.5208972 * cos(twoPi * ratio)) + (0.1980399 * cos(fourPi * ratio));
 			break;
-		case FFT_WIN_TYP_WELCH: /* welch */
+		case FFT_WIN_TYP_WELCH: // welch
 			weighingFactor = 1.0 - sq((indexMinusOne - samplesMinusOne / 2.0) / (samplesMinusOne / 2.0));
 			break;
 		}
@@ -148,31 +265,36 @@ void arduinoFFT::Windowing(double *vData, uint16_t samples, uint8_t windowType,
 	}
 }
 
-void arduinoFFT::PrintVector(double *vData, uint16_t samples, double samplingFrequency)
+double arduinoFFT::MajorPeak()
 {
-	PrintArray(vData,samples, samplingFrequency, SCL_INDEX);
+	double maxY = 0;
-}
+	uint16_t IndexOfMaxY = 0;
-
+	//If sampling_frequency = 2 * max_frequency in signal,
-void arduinoFFT::PrintSignal(double *vData, uint16_t samples, double samplingFrequency)
+	//value would be stored at position samples/2
-{
+	for (uint16_t i = 1; i < ((this->_samples >> 1) + 1); i++) {
-	PrintArray(vData,samples, samplingFrequency, SCL_TIME);
+		if ((this->_vReal[i-1] < this->_vReal[i]) && (this->_vReal[i] > this->_vReal[i+1])) {
-}
+			if (this->_vReal[i] > maxY) {
-
+				maxY = this->_vReal[i];
-void arduinoFFT::PrintSpectrum(double *vData, uint16_t samples, double samplingFrequency)
+				IndexOfMaxY = i;
-{
+			}
-	PrintArray(vData,samples, samplingFrequency, SCL_FREQUENCY);
+		}
-}
+	}
-
+	double delta = 0.5 * ((this->_vReal[IndexOfMaxY-1] - this->_vReal[IndexOfMaxY+1]) / (this->_vReal[IndexOfMaxY-1] - (2.0 * this->_vReal[IndexOfMaxY]) + this->_vReal[IndexOfMaxY+1]));
-void arduinoFFT::PlotSpectrum(double *vData, uint16_t samples, double samplingFrequency)
+	double interpolatedX = ((IndexOfMaxY + delta)  * this->_samplingFrequency) / (this->_samples-1);
-{
+	if(IndexOfMaxY==(this->_samples >> 1)) //To improve calculation on edge values
-	PrintArray(vData,samples, samplingFrequency, SCL_PLOT);
+		interpolatedX = ((IndexOfMaxY + delta)  * this->_samplingFrequency) / (this->_samples);
+	// retuned value: interpolated frequency peak apex
+	return(interpolatedX);
 }
 
 double arduinoFFT::MajorPeak(double *vD, uint16_t samples, double samplingFrequency)
 {
+	#warning("This method is deprecated and will be removed on future revisions.")
 	double maxY = 0;
 	uint16_t IndexOfMaxY = 0;
-	for (uint16_t i = 1; i < ((samples >> 1) - 1); i++) {
+	//If sampling_frequency = 2 * max_frequency in signal,
+	//value would be stored at position samples/2
+	for (uint16_t i = 1; i < ((samples >> 1) + 1); i++) {
 		if ((vD[i-1] < vD[i]) && (vD[i] > vD[i+1])) {
 			if (vD[i] > maxY) {
 				maxY = vD[i];
@@ -182,19 +304,22 @@ double arduinoFFT::MajorPeak(double *vD, uint16_t samples, double samplingFreque
 	}
 	double delta = 0.5 * ((vD[IndexOfMaxY-1] - vD[IndexOfMaxY+1]) / (vD[IndexOfMaxY-1] - (2.0 * vD[IndexOfMaxY]) + vD[IndexOfMaxY+1]));
 	double interpolatedX = ((IndexOfMaxY + delta)  * samplingFrequency) / (samples-1);
-	/* retuned value: interpolated frequency peak apex */
+	if(IndexOfMaxY==(samples >> 1)) //To improve calculation on edge values
+		interpolatedX = ((IndexOfMaxY + delta)  * samplingFrequency) / (samples);
+	// returned value: interpolated frequency peak apex
 	return(interpolatedX);
 }
 
 uint8_t arduinoFFT::Exponent(uint16_t value)
 {
-	/* Calculates the base 2 logarithm of a value */
+	#warning("This method will not be accessible on future revisions.")
+	// Calculates the base 2 logarithm of a value
 	uint8_t result = 0;
 	while (((value >> result) & 1) != 1) result++;
 	return(result);
 }
 
-/* Private functions */
+// Private functions
 
 void arduinoFFT::Swap(double *x, double *y)
 {
@@ -202,35 +327,3 @@ void arduinoFFT::Swap(double *x, double *y)
 	*x = *y;
 	*y = temp;
 }
-
-void arduinoFFT::PrintArray(double *vData, uint16_t samples, double samplingFrequency, uint8_t scaleType)
-{
-	uint16_t bufferSize = samples;
-	if((scaleType == SCL_FREQUENCY)||(scaleType == SCL_PLOT))
-		bufferSize = bufferSize>>1;
-	for (uint16_t i = 0; i < bufferSize; i++)
-	{
-		double abscissa;
-		switch (scaleType)
-		{
-			case SCL_INDEX:
-				abscissa = (i * 1.0);
-			break;
-			case SCL_TIME:
-				abscissa = ((i * 1.0) / samplingFrequency);
-			break;
-			case SCL_FREQUENCY:
-			case SCL_PLOT:
-				abscissa = ((i * 1.0 * samplingFrequency) / samples);
-			break;
-		}
-		if(scaleType!=SCL_PLOT){
-			Serial.print(abscissa, 6);
-			if(scaleType==SCL_FREQUENCY)
-			Serial.print(" Hz");
-			Serial.print(" ");
-		}
-		Serial.println(vData[i], 4);
-	}
-	Serial.println();
-}

src/arduinoFFT.h

@@ -42,10 +42,7 @@
 /* Custom constants */
 #define FFT_FORWARD 0x01
 #define FFT_REVERSE 0x00
-#define SCL_INDEX 0x00
+
-#define SCL_TIME 0x01
-#define SCL_FREQUENCY 0x02
-#define SCL_PLOT 0x03
 /* Windowing type */
 #define FFT_WIN_TYP_RECTANGLE 0x00 /* rectangle (Box car) */
 #define FFT_WIN_TYP_HAMMING 0x01 /* hamming */
@@ -62,26 +59,31 @@ class arduinoFFT {
 public:
 	/* Constructor */
 	arduinoFFT(void);
+	arduinoFFT(double *vReal, double *vImag, uint16_t samples, double samplingFrequency);
 	/* Destructor */
 	~arduinoFFT(void);
 	/* Functions */
+	uint8_t Revision(void);
+	uint8_t Exponent(uint16_t value);
 	void ComplexToMagnitude(double *vReal, double *vImag, uint16_t samples);
 	void Compute(double *vReal, double *vImag, uint16_t samples, uint8_t dir);
 	void Compute(double *vReal, double *vImag, uint16_t samples, uint8_t power, uint8_t dir);
-	void PrintVector(double *vData, uint16_t samples, double samplingFrequency);
-	void PrintSignal(double *vData, uint16_t samples, double samplingFrequency);
-	void PrintSpectrum(double *vData, uint16_t samples, double samplingFrequency);
-	void PlotSpectrum(double *vData, uint16_t samples, double samplingFrequency);
 	double MajorPeak(double *vD, uint16_t samples, double samplingFrequency);
-	uint8_t Revision(void);
 	void Windowing(double *vData, uint16_t samples, uint8_t windowType, uint8_t dir);
-	uint8_t Exponent(uint16_t value);
+	void ComplexToMagnitude();
+	void Compute(uint8_t dir);
+	double MajorPeak();
+	void Windowing(uint8_t windowType, uint8_t dir);
 
 private:
+	/* Variables */
+	uint16_t _samples;
+	double _samplingFrequency;
+	double *_vReal;
+	double *_vImag;
+	uint8_t _power;
 	/* Functions */
 	void Swap(double *x, double *y);
-	void PrintArray(double *vData, uint16_t samples, double samplingFrequency, uint8_t scaleType);
-
 };
 
 #endif