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一、什么是蜂鸣器？

蜂鸣器是一种将电信号转换为声音信号的器件，常用来产生设备的按键音、报警音等提示信号。

蜂鸣器按驱动方式可分为有源蜂鸣器和无源蜂鸣器：

有源蜂鸣器：内部自带振荡源，将正负极接上直流电压即可持续发声，频率固定。
无源蜂鸣器：内部不带振荡源，需要控制器提供振荡脉冲才可发声，调整提供振荡脉冲的频率，可发出不同频率的声音。

二、51蜂鸣器原理：

同理，一种单片机一个样，本篇只讲51。

蜂鸣器原理图：很简单，BZ接通即响，BZ则接通到五线四相步进电机上。

五线四相步进电机：BZ由P1_5控制，给1则蜂鸣器响。

内部原理图：（扩展）

三、音高：控制频率：

方法：定时器中断：

sbit Buzzer = P1 ^ 5;//蜂鸣器//低音L，中音M，高音H，后面为数组FreqTable的对应位置
#define P   0
#define L1  1     //低音1
#define L1_ 2     //1#，右边'_'标明#
#define L2  3
#define L2_ 4
#define L3  5
#define L4  6
#define L4_ 7
#define L5  8
#define L5_ 9
#define L6  10
#define L6_ 11
#define L7  12
#define M1  13     //中音1
#define M1_ 14     //1#
#define M2  15
#define M2_ 16
#define M3  17
#define M4  18
#define M4_ 19
#define M5  20
#define M5_ 21
#define M6  22
#define M6_ 23
#define M7  24
#define H1  25     //高音1
#define H1_ 26     //1#
#define H2  27
#define H2_ 28
#define H3  29
#define H4  30
#define H4_ 31
#define H5  32
#define H5_ 33
#define H6  34
#define H6_ 35
#define H7  36//前面0的目的是休止，后面是，音高所对应的，定时器起始时长
unsigned int FreqTable[] = { 0,63628,63731,63835,63928,64021,64103,64185,64260,64331,64400
,64463,64528,64580,64633, 64684, 64732,64777, 64820, 64860, 64898, 64934,64968,65000,
65030,65058, 65085,65110, 65134, 65157, 65178, 65198, 65217,65235,65252,65268, 65283, };void Timer0_Routine() interrupt 1
{if (FreqTable[FreqSelect]){TH0 = FreqTable[FreqSelect] / 256;TL0 = FreqTable[FreqSelect] % 256 + 1;Buzzer = !Buzzer;}
}

三、实战：蜂鸣器播放音乐：小星星

//低音L，中音M，高音H，后面为数组FreqTable的对应位置
#define P   0
#define L1  1     //低音1
#define L1_ 2     //1#，右边'_'标明#
#define L2  3
#define L2_ 4
#define L3  5
#define L4  6
#define L4_ 7
#define L5  8
#define L5_ 9
#define L6  10
#define L6_ 11
#define L7  12
#define M1  13     //中音1
#define M1_ 14     //1#
#define M2  15
#define M2_ 16
#define M3  17
#define M4  18
#define M4_ 19
#define M5  20
#define M5_ 21
#define M6  22
#define M6_ 23
#define M7  24
#define H1  25     //高音1
#define H1_ 26     //1#
#define H2  27
#define H2_ 28
#define H3  29
#define H4  30
#define H4_ 31
#define H5  32
#define H5_ 33
#define H6  34
#define H6_ 35
#define H7  36//前面0的目的是休止，后面是，音高所对应的，定时器起始时长
unsigned int FreqTable[] = { 0,63628,63731,63835,63928,64021,64103,64185,64260,64331,64400
,64463,64528,64580,64633, 64684, 64732,64777, 64820, 64860, 64898, 64934,64968,65000,
65030,65058, 65085,65110, 65134, 65157, 65178, 65198, 65217,65235,65252,65268, 65283, };unsigned char Music_LittleStar[] = { 13,1,13,1,20,1,20,1,22,1,22,1,20,2,18,1,18,1,17,1,17,1,15,1,15,1,13,2,0xFF };
unsigned char FreqSelect, MusicSelect;void main()
{Time0_Init();while (1){if (Music[MusicSelect] != 0xFF){FreqSelect = Music[MusicSelect];MusicSelect++;Delay(500 * Music[++MusicSelect]);//停顿，让同一音符分开TR0 = 0;Buzzer = 0;Delay(50);TR0 = 1;} else{//播放结束TR0 = 0;Buzzer = 0;while (1);}}
}void Timer0_Routine() interrupt 1
{if (FreqTable[FreqSelect]){TH0 = FreqTable[FreqSelect] / 256;TL0 = FreqTable[FreqSelect] % 256 + 1;Buzzer = !Buzzer;}
}