STM32使用无源蜂鸣器演奏歌曲

上一次使用了有源蜂鸣器，只能发出固定的”滴滴“声，当然不能满足于此呀。使用无源蜂鸣器，只要输出不同频率的PWM波，即可发出不同的音符。

不同的音符组合起来就是一个曲子了。

改变PWM的音调，可以输出Do re mi fa so la si do这样的7个音符，还可以输出不同音调的Do re mi fa so la si do。

在实例程序里面，我定义了低中高三个音阶。音符的频率则是mbed提供的。已经宏定义好了。

只要改变PWM的输出周期，即可发出不同的音调（频率是周期的倒数）。

为了方便起见，写了一个音阶类（Pitch），虚基类。里面有一个perform函数，参数是音符和持续时间。例如要发出Do这个声音，持续0.5s，只要perform(1,0.5)就好。

还有一个Stop函数，停止响声0.5s则stop（0.5），无参数则直接停止。后面的Low、Mid、High类则是派生类，实现了Pitch的虚函数。

程序里面包括：

1、发出低中高三个声调的Do re mi fa so la si do音。

2、中音版的小星星。

3、低音版的小星星。

#include "mbed.h"

#define NOTE_B0  31

#define NOTE_C1  33

#define NOTE_CS1 35

#define NOTE_D1  37

#define NOTE_DS1 39

#define NOTE_E1  41

#define NOTE_F1  44

#define NOTE_FS1 46

#define NOTE_G1  49

#define NOTE_GS1 52

#define NOTE_A1  55

#define NOTE_AS1 58

#define NOTE_B1  62

#define NOTE_C2  65

#define NOTE_CS2 69

#define NOTE_D2  73

#define NOTE_DS2 78

#define NOTE_E2  82

#define NOTE_F2  87

#define NOTE_FS2 93

#define NOTE_G2  98

#define NOTE_GS2 104

#define NOTE_A2  110

#define NOTE_AS2 117

#define NOTE_B2  123

#define NOTE_C3  131

#define NOTE_CS3 139

#define NOTE_D3  147

#define NOTE_DS3 156

#define NOTE_E3  165

#define NOTE_F3  175

#define NOTE_FS3 185

#define NOTE_G3  196

#define NOTE_GS3 208

#define NOTE_A3  220

#define NOTE_AS3 233

#define NOTE_B3  247

#define NOTE_C4  262

#define NOTE_CS4 277

#define NOTE_D4  294

#define NOTE_DS4 311

#define NOTE_E4  330

#define NOTE_F4  349

#define NOTE_FS4 370

#define NOTE_G4  392

#define NOTE_GS4 415

#define NOTE_A4  440

#define NOTE_AS4 466

#define NOTE_B4  494

#define NOTE_C5  523

#define NOTE_CS5 554

#define NOTE_D5  587

#define NOTE_DS5 622

#define NOTE_E5  659

#define NOTE_F5  698

#define NOTE_FS5 740

#define NOTE_G5  784

#define NOTE_GS5 831

#define NOTE_A5  880

#define NOTE_AS5 932

#define NOTE_B5  988

#define NOTE_C6  1047

#define NOTE_CS6 1109

#define NOTE_D6  1175

#define NOTE_DS6 1245

#define NOTE_E6  1319

#define NOTE_F6  1397

#define NOTE_FS6 1480

#define NOTE_G6  1568

#define NOTE_GS6 1661

#define NOTE_A6  1760

#define NOTE_AS6 1865

#define NOTE_B6  1976

#define NOTE_C7  2093

#define NOTE_CS7 2217

#define NOTE_D7  2349

#define NOTE_DS7 2489

#define NOTE_E7  2637

#define NOTE_F7  2794

#define NOTE_FS7 2960

#define NOTE_G7  3136

#define NOTE_GS7 3322

#define NOTE_A7  3520

#define NOTE_AS7 3729

#define NOTE_B7  3951

#define NOTE_C8  4186

#define NOTE_CS8 4435

#define NOTE_D8  4699

#define NOTE_DS8 4978

//7个音符组成了美妙的音乐

//低   Do re mi fa so la si do
int melody[] = {  NOTE_C4, NOTE_D4,NOTE_E4, NOTE_F4, NOTE_G4,NOTE_A4,NOTE_B4,NOTE_C5};

//中   Do re mi fa so la si do
int melody2[] = {  NOTE_C5, NOTE_D5,NOTE_E5, NOTE_F5, NOTE_G5,NOTE_A5,NOTE_B5,NOTE_C6};

//高
int melody3[] = {  NOTE_C6, NOTE_D6,NOTE_E6, NOTE_F6, NOTE_G6,NOTE_A6,NOTE_B6,NOTE_C7};

//PWM输出口
PwmOut m(PB_13);

//音调类
class Pitch{

    public:

      virtual void perfrom(int,double)=;

      void stop(double time = ){

          if(time==)
            m = ;
          else{

            m = ;
            wait(time);  

              }//end else

          }//end stop

};

class Low:public Pitch{

    public:
    void perfrom(int index,double time){

            m.period_us(/melody[index-]);

            m.write(0.5);

            wait(time);

        }

};

class Mid:public Pitch{

    public:
    void perfrom(int index,double time){

            m.period_us(/melody2[index-]);

            m.write(0.5);

            wait(time);

        }

};

class Hig:public Pitch{

    public:
    void perfrom(int index ,double time){

            m.period_us(/melody3[index-]);

            m.write(0.5);

            wait(time);

        }

};

int main()

{
    /*试音
      for (int thisNote = 0; thisNote < 8; thisNote++) {

        m.period_us(1000000/melody[thisNote]);

        m.write(0.5);

        wait(0.5);

      }

      for (int thisNote = 0; thisNote < 8; thisNote++) {

        m.period_us(1000000/melody2[thisNote]);

        m.write(0.5);

        wait(0.5);

      }

      for (int thisNote = 0; thisNote < 8; thisNote++) {

        m.period_us(1000000/melody3[thisNote]);

        m.write(0.5);

        wait(0.5);

      }

    m = 1;
    */

    /*中音版
    Mid mid;

    //11 55 66 5
    mid.perfrom(1,0.5);
    mid.perfrom(1,0.5);
    mid.perfrom(5,0.5);
    mid.perfrom(5,0.5);
    mid.perfrom(6,0.5);
    mid.perfrom(6,0.5);
    mid.perfrom(5,0.8);
    mid.stop(0.2);

    //44 33 22 1
    mid.perfrom(4,0.5);
    mid.perfrom(4,0.5);
    mid.perfrom(3,0.5);
    mid.perfrom(3,0.5);
    mid.perfrom(2,0.5);
    mid.perfrom(2,0.5);
    mid.perfrom(1,0.5);
    mid.stop(0.2);

    //55 44 33 2
    mid.perfrom(5,0.5);
    mid.perfrom(5,0.5);
    mid.perfrom(4,0.5);
    mid.perfrom(4,0.5);
    mid.perfrom(3,0.5);
    mid.perfrom(3,0.5);
    mid.perfrom(2,0.5);
    mid.stop(0.2);

    //55 44 33 2
    mid.perfrom(5,0.5);
    mid.perfrom(5,0.5);
    mid.perfrom(4,0.5);
    mid.perfrom(4,0.5);
    mid.perfrom(3,0.5);
    mid.perfrom(3,0.5);
    mid.perfrom(2,0.5);
    mid.stop(0.2);

    //11 55 66 5
    mid.perfrom(1,0.5);
    mid.perfrom(1,0.5);
    mid.perfrom(5,0.5);
    mid.perfrom(5,0.5);
    mid.perfrom(6,0.5);
    mid.perfrom(6,0.5);
    mid.perfrom(5,0.5);
    mid.stop(0.2);

    //44 33 22 1
    mid.perfrom(4,0.5);
    mid.perfrom(4,0.5);
    mid.perfrom(3,0.5);
    mid.perfrom(3,0.5);
    mid.perfrom(2,0.5);
    mid.perfrom(2,0.5);
    mid.perfrom(1,0.5);

    mid.stop();
    */

    //低音版

    Low low;

    //11 55 66 5
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.8);
    low.stop(0.2);

    //44 33 22 1
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.stop(0.2);

    //55 44 33 2
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.stop(0.2);

    //55 44 33 2
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.stop(0.2);

    //11 55 66 5
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.stop(0.2);

    //44 33 22 1
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);
    low.perfrom(,0.5);

    low.stop();

}

蜂鸣器比较刺耳其实，听久了还是很难受。

在代码里面是不能调节音量的，要调低音量，加个电阻就好。最大的音量是无电阻+高电压。

没法录音，所以还是上图。

效果可以上秒拍听一下：http://video.weibo.com/show?fid=1034:aee9c2288407e28eca7eb89d5ecc8a1d