Add proper API to FFT objects

analyze_fft1024.cpp

@@ -27,18 +27,7 @@
 #include "analyze_fft1024.h"
 #include "sqrt_integer.h"
 #include "utility/dspinst.h"
-#include "arm_math.h"
 
-// TODO: this should be a class member, so more than one FFT can be used
-static arm_cfft_radix4_instance_q15 fft_inst;
-
-void AudioAnalyzeFFT1024::init(void)
-{
-	// TODO: replace this with static const version
-	arm_cfft_radix4_init_q15(&fft_inst, 1024, 0, 1);
-	//state = 0;
-	//outputflag = false;
-}
 
 // 140312 - PAH - slightly faster copy
 static void copy_to_fft_buffer(void *destination, const void *source)
@@ -133,32 +122,6 @@ void AudioAnalyzeFFT1024::update(void)
 		state = 4;
 		break;
 	}
-/*
-	copy_to_fft_buffer(buffer, prevblock->data);
-	copy_to_fft_buffer(buffer+256, block->data);
-	if (window) apply_window_to_fft_buffer(buffer, window);
-	arm_cfft_radix4_q15(&fft_inst, buffer);
-	if (count == 0) {
-		for (int i=0; i < 128; i++) {
-			uint32_t tmp = *((uint32_t *)buffer + i);
-			uint32_t magsq = multiply_16tx16t_add_16bx16b(tmp, tmp);
-			sum[i] = magsq / naverage;
-		}
-	} else {
-		for (int i=0; i < 128; i++) {
-			uint32_t tmp = *((uint32_t *)buffer + i);
-			uint32_t magsq = multiply_16tx16t_add_16bx16b(tmp, tmp);
-			sum[i] += magsq / naverage;
-		}
-	}
-	if (++count == naverage) {
-		count = 0;
-		for (int i=0; i < 128; i++) {
-			output[i] = sqrt_uint32_approx(sum[i]);
-		}
-		outputflag = true;
-	}
-*/
 }
 
 

analyze_fft1024.h

@@ -28,6 +28,7 @@
 #define analyze_fft1024_h_
 
 #include "AudioStream.h"
+#include "arm_math.h"
 
 // windows.c
 extern "C" {
@@ -47,10 +48,10 @@ extern const int16_t AudioWindowTukey1024[];
 class AudioAnalyzeFFT1024 : public AudioStream
 {
 public:
-	AudioAnalyzeFFT1024(uint8_t navg = 1, const int16_t *win = AudioWindowHanning1024)
-	  : AudioStream(1, inputQueueArray), window(win), 
-	    state(0), outputflag(false) { init(); }
-
+	AudioAnalyzeFFT1024() : AudioStream(1, inputQueueArray),
+	  window(AudioWindowHanning1024), state(0), outputflag(false) {
+		arm_cfft_radix4_init_q15(&fft_inst, 1024, 0, 1);
+	}
 	bool available() {
 		if (outputflag == true) {
 			outputflag = false;
@@ -58,6 +59,30 @@ public:
 		}
 		return false;
 	}
+	float read(unsigned int binNumber) {
+		if (binNumber > 511) return 0.0;
+		return (float)(output[binNumber]) * (1.0 / 16384.0);
+	}
+	float read(unsigned int binFirst, unsigned int binLast) {
+		if (binFirst > binLast) {
+			unsigned int tmp = binLast;
+			binLast = binFirst;
+			binFirst = tmp;
+		}
+		if (binFirst > 511) return 0.0;
+		if (binLast > 511) binLast = 511;
+		uint32_t sum = 0;
+		do {
+			sum += output[binFirst++];
+		} while (binFirst < binLast);
+		return (float)sum * (1.0 / 16384.0);
+	}
+	void averageTogether(uint8_t n) {
+		// not implemented yet (may never be, 86 Hz output rate is ok)
+	}
+	void windowFunction(const int16_t *w) {
+		window = w;
+	}
 	virtual void update(void);
 	uint16_t output[512] __attribute__ ((aligned (4)));
 private:
@@ -71,6 +96,7 @@ private:
 	//uint8_t naverage;
 	volatile bool outputflag;
 	audio_block_t *inputQueueArray[1];
+	arm_cfft_radix4_instance_q15 fft_inst;
 };
 
 #endif

analyze_fft256.cpp

@@ -27,18 +27,7 @@
 #include "analyze_fft256.h"
 #include "sqrt_integer.h"
 #include "utility/dspinst.h"
-#include "arm_math.h"
 
-// TODO: this should be a class member, so more than one FFT can be used
-static arm_cfft_radix4_instance_q15 fft_inst;
-
-void AudioAnalyzeFFT256::init(void)
-{
-	// TODO: replace this with static const version
-	arm_cfft_radix4_init_q15(&fft_inst, 256, 0, 1);
-	//state = 0;
-	//outputflag = false;
-}
 
 // 140312 - PAH - slightly faster copy
 static void copy_to_fft_buffer(void *destination, const void *source)

analyze_fft256.h

@@ -28,6 +28,7 @@
 #define analyze_fft256_h_
 
 #include "AudioStream.h"
+#include "arm_math.h"
 
 // windows.c
 extern "C" {
@@ -47,10 +48,11 @@ extern const int16_t AudioWindowTukey256[];
 class AudioAnalyzeFFT256 : public AudioStream
 {
 public:
-	AudioAnalyzeFFT256(uint8_t navg = 8, const int16_t *win = AudioWindowHanning256)
-	  : AudioStream(1, inputQueueArray), window(win), 
-	    prevblock(NULL), count(0), naverage(navg), outputflag(false) { init(); }
-
+	AudioAnalyzeFFT256() : AudioStream(1, inputQueueArray),
+	  window(AudioWindowHanning256), prevblock(NULL), count(0),
+	  naverage(8), outputflag(false) {
+		arm_cfft_radix4_init_q15(&fft_inst, 256, 0, 1);
+	}
 	bool available() {
 		if (outputflag == true) {
 			outputflag = false;
@@ -58,11 +60,34 @@ public:
 		}
 		return false;
 	}
+	float read(unsigned int binNumber) {
+		if (binNumber > 127) return 0.0;
+		return (float)(output[binNumber]) * (1.0 / 16384.0);
+	}
+	float read(unsigned int binFirst, unsigned int binLast) {
+		if (binFirst > binLast) {
+			unsigned int tmp = binLast;
+			binLast = binFirst;
+			binFirst = tmp;
+		}
+		if (binFirst > 127) return 0.0;
+		if (binLast > 127) binLast = 127;
+		uint32_t sum = 0;
+		do {
+			sum += output[binFirst++];
+		} while (binFirst < binLast);
+		return (float)sum * (1.0 / 16384.0);
+	}
+	void averageTogether(uint8_t n) {
+		if (n == 0) n == 1;
+		naverage = n;
+	}
+	void windowFunction(const int16_t *w) {
+		window = w;
+	}
 	virtual void update(void);
-	//uint32_t cycles;
 	uint16_t output[128] __attribute__ ((aligned (4)));
 private:
-	void init(void);
 	const int16_t *window;
 	audio_block_t *prevblock;
 	int16_t buffer[512] __attribute__ ((aligned (4)));
@@ -71,6 +96,7 @@ private:
 	uint8_t naverage;
 	bool outputflag;
 	audio_block_t *inputQueueArray[1];
+	arm_cfft_radix4_instance_q15 fft_inst;
 };
 
 #endif

examples/Analysis/FFT/FFT.ino

@@ -9,21 +9,17 @@ const int myInput = AUDIO_INPUT_LINEIN;
 // Create the Audio components.  These should be created in the
 // order data flows, inputs/sources -> processing -> outputs
 //
-AudioInputI2S       audioInput;         // audio shield: mic or line-in
-AudioAnalyzeFFT256  myFFT(20);
-AudioOutputI2S      audioOutput;        // audio shield: headphones & line-out
+AudioInputI2S          audioInput;         // audio shield: mic or line-in
+AudioSynthWaveformSine sinewave;
+AudioAnalyzeFFT1024    myFFT;
+AudioOutputI2S         audioOutput;        // audio shield: headphones & line-out
 
-// Create Audio connections between the components
-//
-AudioConnection c1(audioInput, 0, audioOutput, 0);
-AudioConnection c2(audioInput, 0, myFFT, 0);
-AudioConnection c3(audioInput, 1, audioOutput, 1);
+// Connect either the live input or synthesized sine wave
+AudioConnection patchCord1(audioInput, 0, myFFT, 0);
+//AudioConnection patchCord1(sinewave, 0, myFFT, 0);
 
-// Create an object to control the audio shield.
-// 
 AudioControlSGTL5000 audioShield;
 
-
 void setup() {
   // Audio connections require memory to work.  For more
   // detailed information, see the MemoryAndCpuUsage example
@@ -33,6 +29,15 @@ void setup() {
   audioShield.enable();
   audioShield.inputSelect(myInput);
   audioShield.volume(0.6);
+
+  // Configure the window algorithm to use
+  myFFT.windowFunction(AudioWindowHanning1024);
+  //myFFT.windowFunction(NULL);
+
+  // Create a synthetic sine wave, for testing
+  // To use this, edit the connections above
+  sinewave.amplitude(0.8);
+  sinewave.frequency(1034.007);
 }
 
 void loop() {
@@ -40,9 +45,10 @@ void loop() {
     // each time new FFT data is available
     // print it all to the Arduino Serial Monitor
     Serial.print("FFT: ");
-    for (int i=0; i<128; i++) {
-      Serial.print(myFFT.output[i]);
-      Serial.print(",");
+    for (int i=0; i<40; i++) {
+      Serial.print(myFFT.read(i));
+      //Serial.print(myFFT.output[i]);
+      Serial.print(" ");
     }
     Serial.println();
   }

gui/list.html

@@ -1512,23 +1512,35 @@
 		<tr class=top><th>Port</th><th>Purpose</th></tr>
 		<tr class=odd><td align=center>In 0</td><td>Signal to convert to frequency bins</td></tr>
 	</table>
-	<h3>Parameters</h3>
-	<table class=doc align=center cellpadding=3>
-		<tr class=top><th>Name</th><th>Type</th><th>Function</th></tr>
-		<tr class=odd><td align=center>Num</td><td>Integer</td><td># FFTs to average</td></tr>
-		<tr class=odd><td align=center>Window</td><td>Array</td><td>Window method to use</td></tr>
-	</table>
-	<p>Extra description...  Section only present if object has params</p>
 	<h3>Functions</h3>
 	<p class=func><span class=keyword>available</span>();</p>
 	<p class=desc>Returns true each time the FFT analysis produces new output data.
 	</p>
+	<p class=func><span class=keyword>read</span>(binNumber);</p>
+	<p class=desc>Read a single frequency bin, from 0 to 127.  The result is scaled
+		so 1.0 represents a full scale sine wave.
+	</p>
+	<p class=func><span class=keyword>read</span>(firstBin, lastBin);</p>
+	<p class=desc>Read several frequency bins, returning their sum.  The higher
+		audio octaves are represented by many bins, which are typically read
+		as a group for audio visualization.
+	</p>
+	<p class=func><span class=keyword>averageTogether</span>(number);</p>
+	<p class=desc>New data is produced very radidly, approximately 344 times
+		per second.  Multiple outputs can be averaged together, so available()
+		returns true at a slower rate.
+	</p>
+	<p class=func><span class=keyword>windowFunction</span>(window);</p>
+	<p class=desc>Set the window function to be used.  AudioWindowHanning256
+		is the default.  Windowing may be disabled by NULL, but windowing
+		should be used for all non-periodic (music) signals, and all periodic
+		signals that are not exact integer division of the sample rate.
+	</p>
+
 	<h3>Notes</h3>
 	<p>The raw 16 bit output data bins may be access with myFFT.output[num], where
 		num is 0 to 127.</p>
 	<p>TODO: caveats about spectral leakage vs frequency precision for arbitrary signals</p>
-	<p>Known bug in the library limits to only a single instance of this object.
-		This bug will be fixed someday... allowing 2 or more FFTs to run on simultaneously.</p>
 	<p>Window Types:
 		<ul>
 		<li><span class=literal>AudioWindowHanning256</span> (default)</li>
@@ -1574,24 +1586,34 @@
 		<tr class=top><th>Port</th><th>Purpose</th></tr>
 		<tr class=odd><td align=center>In 0</td><td>Signal to convert to frequency bins</td></tr>
 	</table>
-	<h3>Parameters</h3>
-	<table class=doc align=center cellpadding=3>
-		<tr class=top><th>Name</th><th>Type</th><th>Function</th></tr>
-		<tr class=odd><td align=center>Num</td><td>Integer</td><td># FFTs to average</td></tr>
-		<tr class=odd><td align=center>Window</td><td>Array</td><td>Window method to use</td></tr>
-	</table>
-	<p>Extra description...  Section only present if object has params</p>
 	<h3>Functions</h3>
 	<p class=func><span class=keyword>available</span>();</p>
 	<p class=desc>Returns true each time the FFT analysis produces new output data.
 	</p>
+	<p class=func><span class=keyword>read</span>(binNumber);</p>
+	<p class=desc>Read a single frequency bin, from 0 to 511.  The result is scaled
+		so 1.0 represents a full scale sine wave.
+	</p>
+	<p class=func><span class=keyword>read</span>(firstBin, lastBin);</p>
+	<p class=desc>Read several frequency bins, returning their sum.  The higher
+		audio octaves are represented by many bins, which are typically read
+		as a group for audio visualization.
+	</p>
+	<p class=func><span class=keyword>averageTogether</span>(number);</p>
+	<p class=desc>This function does nothing.  The 1024 point FFT always
+		updates at approximately 86 times per second.
+	</p>
+	<p class=func><span class=keyword>windowFunction</span>(window);</p>
+	<p class=desc>Set the window function to be used.  AudioWindowHanning1024
+		is the default.  Windowing may be disabled by NULL, but windowing
+		should be used for all non-periodic (music) signals, and all periodic
+		signals that are not exact integer division of the sample rate.
+	</p>
 	<h3>Notes</h3>
 	<p>1024 point FFT uses approx 50% of the CPU power on Teensy 3.1</p>
 	<p>The raw 16 bit output data bins may be access with myFFT.output[num], where
 		num is 0 to 511.</p>
 	<p>TODO: caveats about spectral leakage vs frequency precision for arbitrary signals</p>
-	<p>Known bug in the library limits to only a single instance of this object.
-		This bug will be fixed someday... but 2 instances may not run due to CPU limitation</p>
 	<p>Window Types:
 		<ul>
 		<li><span class=literal>AudioWindowHanning1024</span> (default)</li>