Mirko Pavleski
Published © GPL3+

DIY Simple FFT Spectrum Analyzer on 16x16 LED Matrix

Visually beautiful spectrum analyzer that can also function as an Audio VU Meter and Waterfall Analyzer.

BeginnerFull instructions provided5 hours3,739
DIY Simple FFT Spectrum Analyzer on 16x16 LED Matrix

Things used in this project

Hardware components

ESP32
Espressif ESP32
×1
ws2812b matrix with16x16 Leds
×1
Small microphone board with preamplifier
×1
Pushbutton Switch, Momentary
Pushbutton Switch, Momentary
×1
Slide Switch
Slide Switch
×1
Resistor 10k ohm
Resistor 10k ohm
×2
Resistor 100k ohm
Resistor 100k ohm
×2
Through Hole Resistor, 470 ohm
Through Hole Resistor, 470 ohm
×1

Software apps and online services

Arduino IDE
Arduino IDE

Hand tools and fabrication machines

Soldering iron (generic)
Soldering iron (generic)
Solder Wire, Lead Free
Solder Wire, Lead Free
3D Printer (generic)
3D Printer (generic)

Story

Read more

Custom parts and enclosures

Grille

Schematics

Schematic diagram

Code

Code

C/C++
// (Heavily) adapted from https://github.com/G6EJD/ESP32-8266-Audio-Spectrum-Display/blob/master/ESP32_Spectrum_Display_02.ino
// Adjusted to allow brightness changes on press+hold, Auto-cycle for 3 button presses within 2 seconds
// Edited to add Neomatrix support for easier compatibility with different layouts.

#include <FastLED_NeoMatrix.h>
#include <arduinoFFT.h>
#include <EasyButton.h>

#define SAMPLES         1024          // Must be a power of 2
#define SAMPLING_FREQ   40000         // Hz, must be 40000 or less due to ADC conversion time. Determines maximum frequency that can be analysed by the FFT Fmax=sampleF/2.
#define AMPLITUDE       300          // Depending on your audio source level, you may need to alter this value. Can be used as a 'sensitivity' control.
#define AUDIO_IN_PIN    35            // Signal in on this pin
#define LED_PIN         5             // LED strip data
#define BTN_PIN         4             // Connect a push button to this pin to change patterns
#define LONG_PRESS_MS   200           // Number of ms to count as a long press
#define COLOR_ORDER     GRB           // If colours look wrong, play with this
#define CHIPSET         WS2812B       // LED strip type
#define MAX_MILLIAMPS   2000          // Careful with the amount of power here if running off USB port
const int BRIGHTNESS_SETTINGS[3] = {5, 70, 200};  // 3 Integer array for 3 brightness settings (based on pressing+holding BTN_PIN)
#define LED_VOLTS       5             // Usually 5 or 12
#define NUM_BANDS       16            // To change this, you will need to change the bunch of if statements describing the mapping from bins to bands
#define NOISE           500           // Used as a crude noise filter, values below this are ignored
const uint8_t kMatrixWidth = 16;                          // Matrix width
const uint8_t kMatrixHeight = 16;                         // Matrix height
#define NUM_LEDS       (kMatrixWidth * kMatrixHeight)     // Total number of LEDs
#define BAR_WIDTH      (kMatrixWidth  / (NUM_BANDS - 1))  // If width >= 8 light 1 LED width per bar, >= 16 light 2 LEDs width bar etc
#define TOP            (kMatrixHeight - 0)                // Don't allow the bars to go offscreen
#define SERPENTINE     true                               // Set to false if you're LEDS are connected end to end, true if serpentine

// Sampling and FFT stuff
unsigned int sampling_period_us;
byte peak[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};              // The length of these arrays must be >= NUM_BANDS
int oldBarHeights[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
int bandValues[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
double vReal[SAMPLES];
double vImag[SAMPLES];
unsigned long newTime;
arduinoFFT FFT = arduinoFFT(vReal, vImag, SAMPLES, SAMPLING_FREQ);

// Button stuff
int buttonPushCounter = 0;
bool autoChangePatterns = false;
EasyButton modeBtn(BTN_PIN);

// FastLED stuff
CRGB leds[NUM_LEDS];
DEFINE_GRADIENT_PALETTE( purple_gp ) {
  0,   0, 212, 255,   //blue
255, 179,   0, 255 }; //purple
DEFINE_GRADIENT_PALETTE( outrun_gp ) {
  0, 141,   0, 100,   //purple
127, 255, 192,   0,   //yellow
255,   0,   5, 255 };  //blue
DEFINE_GRADIENT_PALETTE( greenblue_gp ) {
  0,   0, 255,  60,   //green
 64,   0, 236, 255,   //cyan
128,   0,   5, 255,   //blue
192,   0, 236, 255,   //cyan
255,   0, 255,  60 }; //green
DEFINE_GRADIENT_PALETTE( redyellow_gp ) {
  0,   200, 200,  200,   //white
 64,   255, 218,    0,   //yellow
128,   231,   0,    0,   //red
192,   255, 218,    0,   //yellow
255,   200, 200,  200 }; //white
CRGBPalette16 purplePal = purple_gp;
CRGBPalette16 outrunPal = outrun_gp;
CRGBPalette16 greenbluePal = greenblue_gp;
CRGBPalette16 heatPal = redyellow_gp;
uint8_t colorTimer = 0;

// FastLED_NeoMaxtrix - see https://github.com/marcmerlin/FastLED_NeoMatrix for Tiled Matrixes, Zig-Zag and so forth
FastLED_NeoMatrix *matrix = new FastLED_NeoMatrix(leds, kMatrixWidth, kMatrixHeight,
  NEO_MATRIX_TOP        + NEO_MATRIX_RIGHT +
  NEO_MATRIX_ROWS       + NEO_MATRIX_ZIGZAG +
  NEO_TILE_TOP + NEO_TILE_LEFT + NEO_TILE_ROWS);

void setup() {
  Serial.begin(115200);
  FastLED.addLeds<CHIPSET, LED_PIN, COLOR_ORDER>(leds, NUM_LEDS).setCorrection(TypicalSMD5050);
  FastLED.setMaxPowerInVoltsAndMilliamps(LED_VOLTS, MAX_MILLIAMPS);
  FastLED.setBrightness(BRIGHTNESS_SETTINGS[1]);
  FastLED.clear();

  modeBtn.begin();
  modeBtn.onPressed(changeMode);
  modeBtn.onPressedFor(LONG_PRESS_MS, brightnessButton);
  modeBtn.onSequence(3, 2000, startAutoMode);
  modeBtn.onSequence(5, 2000, brightnessOff);
  sampling_period_us = round(1000000 * (1.0 / SAMPLING_FREQ));
}

void changeMode() {
  Serial.println("Button pressed");
  if (FastLED.getBrightness() == 0) FastLED.setBrightness(BRIGHTNESS_SETTINGS[0]);  //Re-enable if lights are "off"
  autoChangePatterns = false;
  buttonPushCounter = (buttonPushCounter + 1) % 6;
}

void startAutoMode() {
  autoChangePatterns = true;
}

void brightnessButton() {
  if (FastLED.getBrightness() == BRIGHTNESS_SETTINGS[2])  FastLED.setBrightness(BRIGHTNESS_SETTINGS[0]);
  else if (FastLED.getBrightness() == BRIGHTNESS_SETTINGS[0]) FastLED.setBrightness(BRIGHTNESS_SETTINGS[1]);
  else if (FastLED.getBrightness() == BRIGHTNESS_SETTINGS[1]) FastLED.setBrightness(BRIGHTNESS_SETTINGS[2]);
  else if (FastLED.getBrightness() == 0) FastLED.setBrightness(BRIGHTNESS_SETTINGS[0]); //Re-enable if lights are "off"
}

void brightnessOff(){
  FastLED.setBrightness(0);  //Lights out
}

void loop() {

  // Don't clear screen if waterfall pattern, be sure to change this is you change the patterns / order
  if (buttonPushCounter != 5) FastLED.clear();

  modeBtn.read();

  // Reset bandValues[]
  for (int i = 0; i<NUM_BANDS; i++){
    bandValues[i] = 0;
  }

  // Sample the audio pin
  for (int i = 0; i < SAMPLES; i++) {
    newTime = micros();
    vReal[i] = analogRead(AUDIO_IN_PIN); // A conversion takes about 9.7uS on an ESP32
    vImag[i] = 0;
    while ((micros() - newTime) < sampling_period_us) { /* chill */ }
  }

  // Compute FFT
  FFT.DCRemoval();
  FFT.Windowing(FFT_WIN_TYP_HAMMING, FFT_FORWARD);
  FFT.Compute(FFT_FORWARD);
  FFT.ComplexToMagnitude();

  // Analyse FFT results
  for (int i = 2; i < (SAMPLES/2); i++){       // Don't use sample 0 and only first SAMPLES/2 are usable. Each array element represents a frequency bin and its value the amplitude.
    if (vReal[i] > NOISE) {                    // Add a crude noise filter

    /*8 bands, 12kHz top band
      if (i<=3 )           bandValues[0]  += (int)vReal[i];
      if (i>3   && i<=6  ) bandValues[1]  += (int)vReal[i];
      if (i>6   && i<=13 ) bandValues[2]  += (int)vReal[i];
      if (i>13  && i<=27 ) bandValues[3]  += (int)vReal[i];
      if (i>27  && i<=55 ) bandValues[4]  += (int)vReal[i];
      if (i>55  && i<=112) bandValues[5]  += (int)vReal[i];
      if (i>112 && i<=229) bandValues[6]  += (int)vReal[i];
      if (i>229          ) bandValues[7]  += (int)vReal[i];*/

    //16 bands, 12kHz top band
      if (i<=2 )           bandValues[0]  += (int)vReal[i];
      if (i>2   && i<=3  ) bandValues[1]  += (int)vReal[i];
      if (i>3   && i<=5  ) bandValues[2]  += (int)vReal[i];
      if (i>5   && i<=7  ) bandValues[3]  += (int)vReal[i];
      if (i>7   && i<=9  ) bandValues[4]  += (int)vReal[i];
      if (i>9   && i<=13 ) bandValues[5]  += (int)vReal[i];
      if (i>13  && i<=18 ) bandValues[6]  += (int)vReal[i];
      if (i>18  && i<=25 ) bandValues[7]  += (int)vReal[i];
      if (i>25  && i<=36 ) bandValues[8]  += (int)vReal[i];
      if (i>36  && i<=50 ) bandValues[9]  += (int)vReal[i];
      if (i>50  && i<=69 ) bandValues[10] += (int)vReal[i];
      if (i>69  && i<=97 ) bandValues[11] += (int)vReal[i];
      if (i>97  && i<=135) bandValues[12] += (int)vReal[i];
      if (i>135 && i<=189) bandValues[13] += (int)vReal[i];
      if (i>189 && i<=264) bandValues[14] += (int)vReal[i];
      if (i>264          ) bandValues[15] += (int)vReal[i];
    }
  }

  // Process the FFT data into bar heights
  for (byte band = 0; band < NUM_BANDS; band++) {

    // Scale the bars for the display
    int barHeight = bandValues[band] / AMPLITUDE;
    if (barHeight > TOP) barHeight = TOP;

    // Small amount of averaging between frames
    barHeight = ((oldBarHeights[band] * 1) + barHeight) / 2;

    // Move peak up
    if (barHeight > peak[band]) {
      peak[band] = min(TOP, barHeight);
    }

    // Draw bars
    switch (buttonPushCounter) {
      case 0:
        rainbowBars(band, barHeight);
        break;
      case 1:
        // No bars on this one
        break;
      case 2:
        purpleBars(band, barHeight);
        break;
      case 3:
        centerBars(band, barHeight);
        break;
      case 4:
        changingBars(band, barHeight);
        break;
      case 5:
        waterfall(band);
        break;
    }

    // Draw peaks
    switch (buttonPushCounter) {
      case 0:
        whitePeak(band);
        break;
      case 1:
        outrunPeak(band);
        break;
      case 2:
        whitePeak(band);
        break;
      case 3:
        // No peaks
        break;
      case 4:
        // No peaks
        break;
      case 5:
        // No peaks
        break;
    }

    // Save oldBarHeights for averaging later
    oldBarHeights[band] = barHeight;
  }

  // Decay peak
  EVERY_N_MILLISECONDS(60) {
    for (byte band = 0; band < NUM_BANDS; band++)
      if (peak[band] > 0) peak[band] -= 1;
    colorTimer++;
  }

  // Used in some of the patterns
  EVERY_N_MILLISECONDS(10) {
    colorTimer++;
  }

  EVERY_N_SECONDS(10) {
    if (autoChangePatterns) buttonPushCounter = (buttonPushCounter + 1) % 6;
  }

  FastLED.show();
}

// PATTERNS BELOW //

void rainbowBars(int band, int barHeight) {
  int xStart = BAR_WIDTH * band;
  for (int x = xStart; x < xStart + BAR_WIDTH; x++) {
    for (int y = TOP; y >= TOP - barHeight; y--) {
      matrix->drawPixel(x, y, CHSV((x / BAR_WIDTH) * (255 / NUM_BANDS), 255, 255));
    }
  }
}

void purpleBars(int band, int barHeight) {
  int xStart = BAR_WIDTH * band;
  for (int x = xStart; x < xStart + BAR_WIDTH; x++) {
    for (int y = TOP; y >= TOP - barHeight; y--) {
      matrix->drawPixel(x, y, ColorFromPalette(purplePal, y * (255 / (barHeight + 1))));
    }
  }
}

void changingBars(int band, int barHeight) {
  int xStart = BAR_WIDTH * band;
  for (int x = xStart; x < xStart + BAR_WIDTH; x++) {
    for (int y = TOP; y >= TOP - barHeight; y--) {
      matrix->drawPixel(x, y, CHSV(y * (255 / kMatrixHeight) + colorTimer, 255, 255));
    }
  }
}

void centerBars(int band, int barHeight) {
  int xStart = BAR_WIDTH * band;
  for (int x = xStart; x < xStart + BAR_WIDTH; x++) {
    if (barHeight % 2 == 0) barHeight--;
    int yStart = ((kMatrixHeight - barHeight) / 2 );
    for (int y = yStart; y <= (yStart + barHeight); y++) {
      int colorIndex = constrain((y - yStart) * (255 / barHeight), 0, 255);
      matrix->drawPixel(x, y, ColorFromPalette(heatPal, colorIndex));
    }
  }
}

void whitePeak(int band) {
  int xStart = BAR_WIDTH * band;
  int peakHeight = TOP - peak[band] - 1;
  for (int x = xStart; x < xStart + BAR_WIDTH; x++) {
    matrix->drawPixel(x, peakHeight, CHSV(0,0,255));
  }
}

void outrunPeak(int band) {
  int xStart = BAR_WIDTH * band;
  int peakHeight = TOP - peak[band] - 1;
  for (int x = xStart; x < xStart + BAR_WIDTH; x++) {
    matrix->drawPixel(x, peakHeight, ColorFromPalette(outrunPal, peakHeight * (255 / kMatrixHeight)));
  }
}

void waterfall(int band) {
  int xStart = BAR_WIDTH * band;
  double highestBandValue = 40000;        // Set this to calibrate your waterfall

  // Draw bottom line
  for (int x = xStart; x < xStart + BAR_WIDTH; x++) {
    matrix->drawPixel(x, 0, CHSV(constrain(map(bandValues[band],0,highestBandValue,160,0),0,160), 255, 255));
  }

  // Move screen up starting at 2nd row from top
  if (band == NUM_BANDS - 1){
    for (int y = kMatrixHeight - 2; y >= 0; y--) {
      for (int x = 0; x < kMatrixWidth; x++) {
        int pixelIndexY = matrix->XY(x, y + 1);
        int pixelIndex = matrix->XY(x, y);
        leds[pixelIndexY] = leds[pixelIndex];
      }
    }
  }
}

Credits

Mirko Pavleski
168 projects • 1373 followers
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