1 | // FFT-based audio visualizer for Adafruit Circuit Playground: uses the |
---|
2 | // built-in mic on A4, 10x NeoPixels for display. Built on the ELM-Chan |
---|
3 | // FFT library for AVR microcontrollers. |
---|
4 | |
---|
5 | // The fast Fourier transform (FFT) algorithm converts a signal from the |
---|
6 | // time domain to the frequency domain -- e.g. turning a sampled audio |
---|
7 | // signal into a visualization of frequencies and magnitudes -- an EQ meter. |
---|
8 | |
---|
9 | // The FFT algorithm itself is handled in the Circuit Playground library; |
---|
10 | // the code here is mostly for converting that function's output into |
---|
11 | // animation. In most AV gear it's usually done with bargraph displays; |
---|
12 | // with a 1D output (the 10 NeoPixels) we need to get creative with color |
---|
13 | // and brightness...it won't look great in every situation (seems to work |
---|
14 | // best with LOUD music), but it's colorful and fun to look at. So this |
---|
15 | // code is mostly a bunch of tables and weird fixed-point (integer) math |
---|
16 | // that probably doesn't make much sense even with all these comments. |
---|
17 | |
---|
18 | #include <Adafruit_CircuitPlayground.h> |
---|
19 | #include <Wire.h> |
---|
20 | #include <SPI.h> |
---|
21 | |
---|
22 | // GLOBAL STUFF ------------------------------------------------------------ |
---|
23 | |
---|
24 | // Displaying EQ meter output straight from the FFT may be 'correct,' but |
---|
25 | // isn't always visually interesting (most bins spend most time near zero). |
---|
26 | // Dynamic level adjustment narrows in on a range of values so there's |
---|
27 | // always something going on. The upper and lower range are based on recent |
---|
28 | // audio history, and on a per-bin basis (some may be more active than |
---|
29 | // others, so this keeps one or two "loud" bins from spoiling the rest. |
---|
30 | |
---|
31 | #define BINS 10 // FFT output is filtered down to this many bins |
---|
32 | #define FRAMES 4 // This many FFT cycles are averaged for leveling |
---|
33 | uint8_t lvl[FRAMES][BINS], // Bin levels for the prior #FRAMES frames |
---|
34 | avgLo[BINS], // Pseudo rolling averages for bins -- lower and |
---|
35 | avgHi[BINS], // upper limits -- for dynamic level adjustment. |
---|
36 | frameIdx = 0; // Counter for lvl storage |
---|
37 | |
---|
38 | // CALIBRATION CONSTANTS --------------------------------------------------- |
---|
39 | |
---|
40 | const uint8_t PROGMEM |
---|
41 | // Low-level noise initially subtracted from each of 32 FFT bins |
---|
42 | noise[] = { 0x04,0x03,0x03,0x03, 0x02,0x02,0x02,0x02, |
---|
43 | 0x02,0x02,0x02,0x02, 0x01,0x01,0x01,0x01, |
---|
44 | 0x01,0x01,0x01,0x01, 0x01,0x01,0x01,0x01, |
---|
45 | 0x01,0x01,0x01,0x01, 0x01,0x01,0x01,0x01 }, |
---|
46 | // FFT bins (32) are then filtered down to 10 output bins (to match the |
---|
47 | // number of NeoPixels on Circuit Playground). 10 arrays here, one per |
---|
48 | // output bin. First element of each is the number of input bins to |
---|
49 | // merge, second element is index of first merged bin, remaining values |
---|
50 | // are scaling weights as each input bin is merged into output. The |
---|
51 | // merging also "de-linearizes" the FFT output, so it's closer to a |
---|
52 | // logarithmic scale with octaves evenly-ish spaced, music looks better. |
---|
53 | bin0data[] = { 1, 2, 147 }, |
---|
54 | bin1data[] = { 2, 2, 89, 14 }, |
---|
55 | bin2data[] = { 2, 3, 89, 14 }, |
---|
56 | bin3data[] = { 4, 3, 15, 181, 58, 3 }, |
---|
57 | bin4data[] = { 4, 4, 15, 181, 58, 3 }, |
---|
58 | bin5data[] = { 6, 5, 6, 89, 185, 85, 14, 2 }, |
---|
59 | bin6data[] = { 7, 7, 5, 60, 173, 147, 49, 9, 1 }, |
---|
60 | bin7data[] = { 10, 8, 3, 23, 89, 170, 176, 109, 45, 14, 4, 1 }, |
---|
61 | bin8data[] = { 13, 11, 2, 12, 45, 106, 167, 184, 147, 89, 43, 18, 6, 2, 1 }, |
---|
62 | bin9data[] = { 18, 14, 2, 6, 19, 46, 89, 138, 175, 185, 165, 127, 85, 51, 27, 14, 7, 3, 2, 1 }, |
---|
63 | // Pointers to 10 bin arrays, because PROGMEM arrays-of-arrays are weird: |
---|
64 | * const binData[] = { bin0data, bin1data, bin2data, bin3data, bin4data, |
---|
65 | bin5data, bin6data, bin7data, bin8data, bin9data }, |
---|
66 | // R,G,B values for color wheel covering 10 NeoPixels: |
---|
67 | reds[] = { 0xAD, 0x9A, 0x84, 0x65, 0x00, 0x00, 0x00, 0x00, 0x65, 0x84 }, |
---|
68 | greens[] = { 0x00, 0x66, 0x87, 0x9E, 0xB1, 0x87, 0x66, 0x00, 0x00, 0x00 }, |
---|
69 | blues[] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0xC3, 0xE4, 0xFF, 0xE4, 0xC3 }, |
---|
70 | gamma8[] = { // Gamma correction improves the appearance of midrange colors |
---|
71 | 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, |
---|
72 | 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, |
---|
73 | 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, |
---|
74 | 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x03, 0x03, 0x03, 0x03, |
---|
75 | 0x03, 0x03, 0x04, 0x04, 0x04, 0x04, 0x05, 0x05, 0x05, 0x05, 0x05, 0x06, |
---|
76 | 0x06, 0x06, 0x06, 0x07, 0x07, 0x07, 0x08, 0x08, 0x08, 0x09, 0x09, 0x09, |
---|
77 | 0x0A, 0x0A, 0x0A, 0x0B, 0x0B, 0x0B, 0x0C, 0x0C, 0x0D, 0x0D, 0x0D, 0x0E, |
---|
78 | 0x0E, 0x0F, 0x0F, 0x10, 0x10, 0x11, 0x11, 0x12, 0x12, 0x13, 0x13, 0x14, |
---|
79 | 0x14, 0x15, 0x15, 0x16, 0x16, 0x17, 0x18, 0x18, 0x19, 0x19, 0x1A, 0x1B, |
---|
80 | 0x1B, 0x1C, 0x1D, 0x1D, 0x1E, 0x1F, 0x1F, 0x20, 0x21, 0x22, 0x22, 0x23, |
---|
81 | 0x24, 0x25, 0x26, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2A, 0x2B, 0x2C, 0x2D, |
---|
82 | 0x2E, 0x2F, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, |
---|
83 | 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F, 0x40, 0x41, 0x42, 0x44, 0x45, 0x46, |
---|
84 | 0x47, 0x48, 0x49, 0x4B, 0x4C, 0x4D, 0x4E, 0x50, 0x51, 0x52, 0x54, 0x55, |
---|
85 | 0x56, 0x58, 0x59, 0x5A, 0x5C, 0x5D, 0x5E, 0x60, 0x61, 0x63, 0x64, 0x66, |
---|
86 | 0x67, 0x69, 0x6A, 0x6C, 0x6D, 0x6F, 0x70, 0x72, 0x73, 0x75, 0x77, 0x78, |
---|
87 | 0x7A, 0x7C, 0x7D, 0x7F, 0x81, 0x82, 0x84, 0x86, 0x88, 0x89, 0x8B, 0x8D, |
---|
88 | 0x8F, 0x91, 0x92, 0x94, 0x96, 0x98, 0x9A, 0x9C, 0x9E, 0xA0, 0xA2, 0xA4, |
---|
89 | 0xA6, 0xA8, 0xAA, 0xAC, 0xAE, 0xB0, 0xB2, 0xB4, 0xB6, 0xB8, 0xBA, 0xBC, |
---|
90 | 0xBF, 0xC1, 0xC3, 0xC5, 0xC7, 0xCA, 0xCC, 0xCE, 0xD1, 0xD3, 0xD5, 0xD7, |
---|
91 | 0xDA, 0xDC, 0xDF, 0xE1, 0xE3, 0xE6, 0xE8, 0xEB, 0xED, 0xF0, 0xF2, 0xF5, |
---|
92 | 0xF7, 0xFA, 0xFC, 0xFF }; |
---|
93 | const uint16_t PROGMEM |
---|
94 | // Scaling values applied to each FFT bin (32) after noise subtraction |
---|
95 | // but prior to merging/filtering. When multiplied by these values, |
---|
96 | // then divided by 256, these tend to produce outputs in the 0-255 |
---|
97 | // range (VERY VERY "ISH") at normal listening levels. These were |
---|
98 | // determined empirically by throwing lots of sample audio at it. |
---|
99 | binMul[] = { 405, 508, 486, 544, 533, 487, 519, 410, |
---|
100 | 481, 413, 419, 410, 397, 424, 412, 411, |
---|
101 | 511, 591, 588, 577, 554, 529, 524, 570, |
---|
102 | 546, 559, 511, 552, 439, 488, 483, 547, }, |
---|
103 | // Sums of bin weights for bin-merging tables above. |
---|
104 | binDiv[] = { 147, 103, 103, 257, 257, 381, 444, 634, 822, 1142 }; |
---|
105 | |
---|
106 | // SETUP FUNCTION - runs once ---------------------------------------------- |
---|
107 | |
---|
108 | void setup() { |
---|
109 | CircuitPlayground.begin(); |
---|
110 | CircuitPlayground.setBrightness(255); |
---|
111 | CircuitPlayground.clearPixels(); |
---|
112 | |
---|
113 | // Initialize rolling average ranges |
---|
114 | uint8_t i; |
---|
115 | for(i=0; i<BINS; i++) { |
---|
116 | avgLo[i] = 0; |
---|
117 | avgHi[i] = 255; |
---|
118 | } |
---|
119 | for(i=0; i<FRAMES; i++) { |
---|
120 | memset(&lvl[i], 127, sizeof(lvl[i])); |
---|
121 | } |
---|
122 | } |
---|
123 | |
---|
124 | // LOOP FUNCTION - runs over and over - does animation --------------------- |
---|
125 | |
---|
126 | void loop() { |
---|
127 | uint16_t spectrum[32]; // FFT spectrum output buffer |
---|
128 | |
---|
129 | CircuitPlayground.mic.fft(spectrum); |
---|
130 | |
---|
131 | // spectrum[] is now raw FFT output, 32 bins. |
---|
132 | |
---|
133 | // Remove noise and apply EQ levels |
---|
134 | uint8_t i, N; |
---|
135 | uint16_t S; |
---|
136 | for(i=0; i<32; i++) { |
---|
137 | N = pgm_read_byte(&noise[i]); |
---|
138 | if(spectrum[i] > N) { // Above noise threshold: scale & clip |
---|
139 | S = ((spectrum[i] - N) * |
---|
140 | (uint32_t)pgm_read_word(&binMul[i])) >> 8; |
---|
141 | spectrum[i] = (S < 255) ? S : 255; |
---|
142 | } else { // Below noise threshold: clip |
---|
143 | spectrum[i] = 0; |
---|
144 | } |
---|
145 | } |
---|
146 | // spectrum[] is now noise-filtered, scaled & clipped |
---|
147 | // FFT output, in range 0-255, still 32 bins. |
---|
148 | |
---|
149 | // Filter spectrum[] from 32 elements down to 10, |
---|
150 | // make pretty colors out of it: |
---|
151 | |
---|
152 | uint16_t sum, level; |
---|
153 | uint8_t j, minLvl, maxLvl, nBins, binNum, *data; |
---|
154 | |
---|
155 | for(i=0; i<BINS; i++) { // For each output bin (and each pixel)... |
---|
156 | data = (uint8_t *)pgm_read_word(&binData[i]); |
---|
157 | nBins = pgm_read_byte(&data[0]); // Number of input bins to merge |
---|
158 | binNum = pgm_read_byte(&data[1]); // Index of first input bin |
---|
159 | data += 2; |
---|
160 | for(sum=0, j=0; j<nBins; j++) { |
---|
161 | sum += spectrum[binNum++] * pgm_read_byte(&data[j]); // Total |
---|
162 | } |
---|
163 | sum /= pgm_read_word(&binDiv[i]); // Average |
---|
164 | lvl[frameIdx][i] = sum; // Save for rolling averages |
---|
165 | minLvl = maxLvl = lvl[0][i]; // Get min and max range for bin |
---|
166 | for(j=1; j<FRAMES; j++) { // from prior stored frames |
---|
167 | if(lvl[j][i] < minLvl) minLvl = lvl[j][i]; |
---|
168 | else if(lvl[j][i] > maxLvl) maxLvl = lvl[j][i]; |
---|
169 | } |
---|
170 | |
---|
171 | // minLvl and maxLvl indicate the extents of the FFT output for this |
---|
172 | // bin over the past few frames, used for vertically scaling the output |
---|
173 | // graph (so it looks interesting regardless of volume level). If too |
---|
174 | // close together though (e.g. at very low volume levels) the graph |
---|
175 | // becomes super coarse and 'jumpy'...so keep some minimum distance |
---|
176 | // between them (also lets the graph go to zero when no sound playing): |
---|
177 | if((maxLvl - minLvl) < 23) { |
---|
178 | maxLvl = (minLvl < (255-23)) ? minLvl + 23 : 255; |
---|
179 | } |
---|
180 | avgLo[i] = (avgLo[i] * 7 + minLvl) / 8; // Dampen min/max levels |
---|
181 | avgHi[i] = (maxLvl >= avgHi[i]) ? // (fake rolling averages) |
---|
182 | (avgHi[i] * 3 + maxLvl) / 4 : // Fast rise |
---|
183 | (avgHi[i] * 31 + maxLvl) / 32; // Slow decay |
---|
184 | |
---|
185 | // Second fixed-point scale then 'stretches' each bin based on |
---|
186 | // dynamic min/max levels to 0-256 range: |
---|
187 | level = 1 + ((sum <= avgLo[i]) ? 0 : |
---|
188 | 256L * (sum - avgLo[i]) / (long)(avgHi[i] - avgLo[i])); |
---|
189 | // Clip output and convert to color: |
---|
190 | if(level <= 255) { |
---|
191 | uint8_t r = (pgm_read_byte(&reds[i]) * level) >> 8, |
---|
192 | g = (pgm_read_byte(&greens[i]) * level) >> 8, |
---|
193 | b = (pgm_read_byte(&blues[i]) * level) >> 8; |
---|
194 | CircuitPlayground.strip.setPixelColor(i, |
---|
195 | pgm_read_byte(&gamma8[r]), |
---|
196 | pgm_read_byte(&gamma8[g]), |
---|
197 | pgm_read_byte(&gamma8[b])); |
---|
198 | } else { // level = 256, show white pixel OONTZ OONTZ |
---|
199 | CircuitPlayground.strip.setPixelColor(i, 0x56587F); |
---|
200 | } |
---|
201 | } |
---|
202 | CircuitPlayground.strip.show(); |
---|
203 | |
---|
204 | if(++frameIdx >= FRAMES) frameIdx = 0; |
---|
205 | } |
---|