Arduino FFT Spectrum analyzer on VFD display GP1287

1#include "U8g2lib.h"
2#include "fix_fft.h"
3#include <SPI.h>
4int buttonPin = 2; 
5int oldButtonVal = 0;
6// u8g2 set up, bar, line position L & R
7#define LINEY 40
8#define LINEXL 0
9#define LINEXR 256
10
11#define SAMPLES 128
12
13#define AUDIO A0
14 U8G2_GP1287AI_256X50_1_4W_SW_SPI u8g2(U8G2_R0, /* clock=*/ 13, /* data=*/ 11, /* cs=*/ 10, /* dc=*/ 9, /* reset=*/ 8);
15//U8GLIB_ST7920_128X64_1X lcd(EN, RW, CS); // serial use, PSB = GND
16
17char im[SAMPLES];
18char data[SAMPLES];
19int barht[SAMPLES];
20int nPatterns = 2;
21int lightPattern = 1;
22void setup()
23{
24  u8g2.begin(); // inti u8g2
25  u8g2.setContrast(25); 
26  pinMode(2, INPUT_PULLUP);
27}
28
29void loop()
30{
31  static int i, j;
32  int val;
33  
34
35  // get audio data
36  for(i = 0; i < SAMPLES; i++)
37  {
38    val = analogRead(AUDIO)* 50; // 0-1023
39    data[i] = (char)(val/4 - 128); // store as char
40    im[i] = 0; // init all as 0
41  }
42
43
44  // run FFT
45  fix_fft(data, im, 7, 0);
46
47  // extract absolute value of data only, for 64 results
48  for(i = 0; i < SAMPLES/2; i++)
49  {
50    barht[i] = (int)sqrt(data[i] * data[i] + im[i] * im[i]);
51  }
52  
53  for(i = 0, j = 0; i < SAMPLES/2; i++, j += 2)
54  {
55    barht[i] = barht[j] + barht[j + 1];
56  }
57  
58  // u8g2 barchart
59  barchart(SAMPLES/4, barht); // plot SAMPLES / 4 = 32 as barchart gen cannot handle 128 bars
60} 
61
62// plot line and bar at position and height
63void barchart(int n, int bh[])
64{
65  int i, s, w; // bars, spacing and width
66  
67  s = (LINEXR - LINEXL) / n;
68  int buttonVal = digitalRead(buttonPin);
69  if (buttonVal == LOW && oldButtonVal == HIGH) {// button has just been pressed
70    lightPattern = lightPattern + 1;
71  }
72  if (lightPattern > nPatterns) lightPattern = 1;
73  oldButtonVal = buttonVal;
74  
75  switch(lightPattern) {
76    case 1:
77     w = s / 2;
78      break;
79    case 2:
80     w = s / 1;
81  }
82  
83  u8g2.firstPage();
84  do
85  {
86    u8g2.setFont(u8g2_font_6x12_tf);
87    u8g2.drawStr(80, 7, "FFT Audio Spectrum");
88    u8g2.drawLine(LINEXL, LINEY, LINEXR, LINEY);
89    u8g2.drawStr(0, LINEY + 10, "0");
90    u8g2.drawStr(50, LINEY + 10, "1k");
91    u8g2.drawStr(110, LINEY + 10, "2k");
92    u8g2.drawStr(164, LINEY + 10, "3k");
93    u8g2.drawStr(220, LINEY + 10, "4k");
94    u8g2.drawStr(240, LINEY + 10, "Hz");
95    for(i = 0; i < n; i++)
96    {
97      u8g2.drawBox(LINEXL + s * i, LINEY - bh[i], w, bh[i] + 1); // u8glib doesn't accept box height of 0
98    }
99      
100  }while(u8g2.nextPage()); 
101}