First commit.

.pio/libdeps/local/FastLED/examples/Ports/PJRCSpectrumAnalyzer/PJRCSpectrumAnalyzer.ino

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+// LED Audio Spectrum Analyzer Display
+//
+// Creates an impressive LED light show to music input
+//   using Teensy 3.1 with the OctoWS2811 adaptor board
+//   http://www.pjrc.com/store/teensy31.html
+//   http://www.pjrc.com/store/octo28_adaptor.html
+//
+// Line Level Audio Input connects to analog pin A3
+//   Recommended input circuit:
+//   http://www.pjrc.com/teensy/gui/?info=AudioInputAnalog
+//
+// This example code is in the public domain.
+
+#define USE_OCTOWS2811
+#include <OctoWS2811.h>
+#include <FastLED.h>
+#include <Audio.h>
+#include <Wire.h>
+#include <SD.h>
+#include <SPI.h>
+
+// The display size and color to use
+const unsigned int matrix_width = 60;
+const unsigned int matrix_height = 32;
+const unsigned int myColor = 0x400020;
+
+// These parameters adjust the vertical thresholds
+const float maxLevel = 0.5;      // 1.0 = max, lower is more "sensitive"
+const float dynamicRange = 40.0; // total range to display, in decibels
+const float linearBlend = 0.3;   // useful range is 0 to 0.7
+
+CRGB leds[matrix_width * matrix_height];
+
+// Audio library objects
+AudioInputAnalog         adc1(A3);       //xy=99,55
+AudioAnalyzeFFT1024      fft;            //xy=265,75
+AudioConnection          patchCord1(adc1, fft);
+
+
+// This array holds the volume level (0 to 1.0) for each
+// vertical pixel to turn on.  Computed in setup() using
+// the 3 parameters above.
+float thresholdVertical[matrix_height];
+
+// This array specifies how many of the FFT frequency bin
+// to use for each horizontal pixel.  Because humans hear
+// in octaves and FFT bins are linear, the low frequencies
+// use a small number of bins, higher frequencies use more.
+int frequencyBinsHorizontal[matrix_width] = {
+   1,  1,  1,  1,  1,  1,  1,  1,  1,  1,
+   2,  2,  2,  2,  2,  2,  2,  2,  2,  3,
+   3,  3,  3,  3,  4,  4,  4,  4,  4,  5,
+   5,  5,  6,  6,  6,  7,  7,  7,  8,  8,
+   9,  9, 10, 10, 11, 12, 12, 13, 14, 15,
+  15, 16, 17, 18, 19, 20, 22, 23, 24, 25
+};
+
+
+
+// Run setup once
+void setup() {
+  // the audio library needs to be given memory to start working
+  AudioMemory(12);
+
+  // compute the vertical thresholds before starting
+  computeVerticalLevels();
+
+  // turn on the display
+  FastLED.addLeds<OCTOWS2811>(leds,(matrix_width * matrix_height) / 8);
+}
+
+// A simple xy() function to turn display matrix coordinates
+// into the index numbers OctoWS2811 requires.  If your LEDs
+// are arranged differently, edit this code...
+unsigned int xy(unsigned int x, unsigned int y) {
+  if ((y & 1) == 0) {
+    // even numbered rows (0, 2, 4...) are left to right
+    return y * matrix_width + x;
+  } else {
+    // odd numbered rows (1, 3, 5...) are right to left
+    return y * matrix_width + matrix_width - 1 - x;
+  }
+}
+
+// Run repetitively
+void loop() {
+  unsigned int x, y, freqBin;
+  float level;
+
+  if (fft.available()) {
+    // freqBin counts which FFT frequency data has been used,
+    // starting at low frequency
+    freqBin = 0;
+
+    for (x=0; x < matrix_width; x++) {
+      // get the volume for each horizontal pixel position
+      level = fft.read(freqBin, freqBin + frequencyBinsHorizontal[x] - 1);
+
+      // uncomment to see the spectrum in Arduino's Serial Monitor
+      // Serial.print(level);
+      // Serial.print("  ");
+
+      for (y=0; y < matrix_height; y++) {
+        // for each vertical pixel, check if above the threshold
+        // and turn the LED on or off
+        if (level >= thresholdVertical[y]) {
+          leds[xy(x,y)] = CRGB(myColor);
+        } else {
+          leds[xy(x,y)] = CRGB::Black;
+        }
+      }
+      // increment the frequency bin count, so we display
+      // low to higher frequency from left to right
+      freqBin = freqBin + frequencyBinsHorizontal[x];
+    }
+    // after all pixels set, show them all at the same instant
+    FastLED.show();
+    // Serial.println();
+  }
+}
+
+
+// Run once from setup, the compute the vertical levels
+void computeVerticalLevels() {
+  unsigned int y;
+  float n, logLevel, linearLevel;
+
+  for (y=0; y < matrix_height; y++) {
+    n = (float)y / (float)(matrix_height - 1);
+    logLevel = pow10f(n * -1.0 * (dynamicRange / 20.0));
+    linearLevel = 1.0 - n;
+    linearLevel = linearLevel * linearBlend;
+    logLevel = logLevel * (1.0 - linearBlend);
+    thresholdVertical[y] = (logLevel + linearLevel) * maxLevel;
+  }
+}