Question

我正在尝试使用mbed LPC微控制器调整吉他。下面是一个项目示例链接。 https://developer.mbed.org/users/adurand/notebook/guitar-tuner/

但是，我遇到了一些问题。首先，我使用任意波形发生器在每个弦的所需频率下模拟吉他输入。放大器电路构造相同。我也更改了代码以使用Mbed LCD代替诺基亚。我使用示波器验证进入Mbed的AnalogueIn p20的输出是否被放大并且频率正确。这是我遇到问题的地方。

以下是代码（由Andrew Durand负责）：

#include "mbed.h"
#include "adc.h"
#include "C12832.h"
#include <math.h>
#define PI 3.1415
#define SAMPLE_RATE 24000

InterruptIn button1(p12);
C12832 lcd(p5, p7, p6, p8, p11);
DigitalOut myled1(LED1);
DigitalOut myled2(LED2);
DigitalOut myled3(LED3);

//LCD and Other Random Variables
int string_select = 0;
float high, high1, in_tune, in_tune1, in_tune2, in_tune3,
low, low1, note, low_mod, high_mod;
char* key;
int Counter = 0;
int Buffer[6000];

float goertzelFilter(int samples[], float freq, int N) {
    float s_prev = 0.0;
    float s_prev2 = 0.0;
    float coeff,normalizedfreq,power,s;
    int i;
    normalizedfreq = freq / SAMPLE_RATE;
    coeff = 2*cos(2*PI*normalizedfreq);
    for (i=0; i<N; i++) {
        s = samples[i] + coeff * s_prev - s_prev2;
        s_prev2 = s_prev;
        s_prev = s;
    }
    power = s_prev2*s_prev2+s_prev*s_prev-coeff*s_prev*s_prev2;
    return power;
}

ADC adc(SAMPLE_RATE, 1);

void sample_audio(int chan, uint32_t value) {
    Buffer[Counter] = adc.read(p20);
    Counter += 1;
}

void button1_pressed() {
    string_select++;
    if (string_select > 5) string_select = 0;
}

int main() {
    //Interupt for Switching Strings
    button1.mode(PullDown);
    button1.rise(&button1_pressed);

    while (1) {

        switch (string_select) {
            case 0:
                note = 82;
                key= "E2";
                break;
            case 1:
                note = 110;
                key= "A2";
                break;
            case 2:
                note = 147;
                key= "D3";
                break;
            case 3:
                note = 196;
                key= "G3";
                break;
            case 4:
                note = 247;
                key= "B3";
                break;
            case 5:
                note = 330;
                key= "E4";
                break;
        }

        //Prepare for burst mode on all ADC pins and set up interrupt handler (using ADC library from Simon Blandford
        adc.append(sample_audio);
        adc.startmode(0,0);
        adc.burst(1);
        adc.setup(p20,1);

        //start the interrupt and wait for about 4096 samples
        adc.interrupt_state(p20,1);
        wait(.2);

        //Finsh up - Unset pin 20
        adc.interrupt_state(p20,0);
        adc.setup(p20,0);
        int actual_rate = adc.actual_sample_rate();

        //for debugging tell the terminal sample rate and how many samples we took
        printf("Requested max sample rate is %u, actual max sample rate is %u.\n",
               SAMPLE_RATE, actual_rate);
        printf("We did %i samples\n",Counter);

high = 0;
low = 0;
for (int i=3; i<46; i+=3) {
    high1 = goertzelFilter(Buffer, (note + i ), Counter);
    if (high1 > high) high=high1;
}
for (int i=3; i<46; i+=3) {
    low1 = goertzelFilter(Buffer, (note - i ), Counter);
    if (low1 > low) low=low1;
}
        in_tune1 =  goertzelFilter(Buffer, (note+1), Counter);
        in_tune2 =  goertzelFilter(Buffer, note, Counter);
        in_tune3 =  goertzelFilter(Buffer, (note-1), Counter);

        if ((in_tune1 > in_tune2) && (in_tune1 > in_tune3)) in_tune = in_tune1;
        else if ((in_tune2 > in_tune1) && (in_tune2 > in_tune3)) in_tune = in_tune2;
        else in_tune = in_tune3;
        printf("high = %.2f, low = %.2f, in_tune = %.2f", high, low, in_tune);
       high_mod = high/in_tune;
      low_mod = low/in_tune; 
        if ((high_mod > .8)&&(low_mod > .8)) {
            myled1 = 0;
            myled2 = 0;
            myled3 = 0; 
        }
                if ((high_mod < .8)&&(low_mod > .8)) {
            myled1 = 0;
            myled2 = 0;
            myled3 = 0;
        }
        if ((high > in_tune) && (low < in_tune)) {         //Guitar string is at correct frequency
            myled1 = 0;
            myled2 = 1;
            myled3 = 0;

        } else if (high > in_tune) {                     // String is higher than the desired frequency
            myled1 = 1;
            myled2 = 0;
            myled3 = 0;

        } else if (low < in_tune){                     // String is below that of the desired frequency
            myled1 = 0;
            myled2 = 0;
            myled3 = 1;

        } else {                                       // Else no input, display squiggles
            myled1 = 0;
            myled2 = 0;
            myled3 = 0;
        }

        // Display on the LCD
        lcd.cls();
        lcd.locate(0,0);
        lcd.printf("Tuning String: %i", (6-string_select));
        lcd.locate(0,11);
        lcd.printf("%s at %i Hz",key, (int) note);
        lcd.locate(0,23);
        if (myled2) lcd.printf("In Tune!");              // if myled2 is on, guitar is in tune
        else if (myled3) lcd.printf("Too Low ");         // if myled3 is on, guitar is lower than desired tone
        else if (myled1) lcd.printf("Too High");         // if myled1 is on, guitar is higher than desired tone
        else lcd.printf("No Input Detected");                     // corresponds to led case 4 - no guitar input present

        Counter = 0;

    }



}

现在，当我编译程序时，打印消息。但是，LED在＆＃34;太高＆＃34;，＆＃34;太低＆＃34;和波浪线之间交替。我是第一个承认我不是最好的程序员的人，我将在夏天真正开展这项工作。代码可能存在非常严重的问题，或者它可能相对简单。所有投入都表示赞赏。

注意：我没有在面包板上连接去抖电路 - 它连接到我没有使用的诺基亚LCD。我可以使用mbed应用板上的操纵杆改变1-6之间的所需字符串。这样可以吗？或者去抖动电路是否至关重要？再次感谢。

Answer 1

找到low的循环（几乎）与在此代码中找到high的循环相同：

high = 0;
low = 0;
for (int i=3; i<46; i+=3) {
    high1 = goertzelFilter(Buffer, (note + i ), Counter);
    if (high1 > high) high=high1;
}
for (int i=3; i<46; i+=3) {
    low1 = goertzelFilter(Buffer, (note - i ), Counter);
    if (low1 > low) low=low1;
}

我建议low部分应该是这样的

low = FLT_MAX;
for (int i=3; i<46; i+=3) {
    low1 = goertzelFilter(Buffer, (note - i ), Counter);
    if (low1 < low) low=low1;
}

......虽然我可能会误认为low的预期用途。

Mbed Guitar Tuner Code问题？

1 个答案: