arduinoでfft

概要

arduinoでfftやってみた。

参考にしたページ。

写真

サンプルコード

#include "fix_fft.h"
#include <Adafruit_GFX.h>
#include "Adafruit_TFTLCD.h"

#define LCD_CS              A3
#define LCD_CD              A2
#define LCD_WR              A1
#define LCD_RD              A0
#define LCD_RESET           A4
#define BLACK               0x0000
#define BLUE                0x001F
#define RED                 0xF800
#define GREEN               0x07E0
#define CYAN                0x07FF
#define MAGENTA             0xF81F
#define YELLOW              0xFFE0
#define WHITE               0xFFFF

Adafruit_TFTLCD tft(LCD_CS, LCD_CD, LCD_WR, LCD_RD, LCD_RESET);

#define SAMPLING_FREQUENCY      15000
#define TIME_FACTOR             2
#define SCALE_FACTOR            8
#ifdef LOG_OUTPUT
const float log_scale = 64. / log(64. / SCALE_FACTOR + 1.);
#endif
const float coeff = 1. / TIME_FACTOR;
const float anti_coeff = (TIME_FACTOR - 1.) / TIME_FACTOR;
const unsigned int sampling_period_us = round(1000000 * (2.0 / SAMPLING_FREQUENCY));
int8_t data[64],
    buff[32],
    peak[32];
unsigned long microseconds;
int summ,
    avg;
const char SPLASH_TITLE[] = "SPECTRUM SPEAKER\n @nori-dev-akg";
unsigned long t0;

void setup() {
    OSCCAL = 250;
    ADCSRA &= ~(bit(ADPS0) | bit(ADPS1) | bit(ADPS2));
    ADCSRA |= bit(ADPS2);
    ADCSRA |= bit(ADPS0);
    tft.reset();
    uint16_t identifier = 0x9341;
    tft.begin(identifier);
    tft.fillScreen(BLACK);
    tft.setTextColor(WHITE);
    tft.setTextSize(2);
    //tft.setRotation(3);
    t0 = millis();
};

void loop() {
    tft.fillScreen(BLACK);
    summ = 0;
    for (int i = 0; i < 64; i++)
    {
        microseconds = micros();
        int val = analogRead(A0);
   val = random(256);
        data[i] = (val >> 2) - 128;
        summ += data[i];
        while (micros() < (microseconds + sampling_period_us))
        {
        }
    }
    avg = summ / 64;
    for (int i = 0; i < 64; i++)
    {
        data[i] -= avg;
    }
    fix_fftr(data, 6, 0);
    int8_t reordered[32];
    for (int i = 0; i < 32; i++)
    {
        if (i % 2 != 0)
            reordered[i] = data[i / 2 + 16];
        else
            reordered[i] = data[i / 2];
    }
    for (int i = 0; i < 32; i++)
        data[i] = reordered[i];
    for (int count = 0; count < 32; count++)
    {
        if (data[count] < 0)
            data[count] = 0;
#ifdef LOG_OUTPUT
        else
            data[count] = log_scale * log((float) (data[count] + 1));
#else
        else
            data[count] *= SCALE_FACTOR;
#endif
        data[count] = (float) buff[count] * anti_coeff + (float) data[count] * coeff;
        buff[count] = data[count];
        if (data[count] > 63)
            data[count] = 63;
    }
    uint8_t x,
        y;
    int d;
    for (int i = 0; i < 32; i++)
    {
        d = data[i] / 2;
        x = i * 8;
        y = 200 - (d + 1) * 4;
        tft.fillRect(x, y, 7, 200 - y, WHITE);
        peak[i] = (peak[i] > y || peak[i] == 0) ? y : peak[i];
        //tft.drawLine(x, peak[i], x + 2, peak[i], RED);
    }
    unsigned long t = millis();
    if (t - t0 > 200)
    {
        for (int i = 0; i < 32; i++)
        {
            peak[i]++;
            if (peak[i] > 31)
                peak[i] = 31;
        }
        t0 = t;
    }
 delay(300);
}

以上。