物理學中我們知道，頻率增加（或降低）一倍聲音就提高{或降低）8度。
因為單片機用的是二進制，左移或右移就是增減幾倍。所以頻率就同比例增減。
下面以播放《祝你平安》為例：其實實現起來非常簡單，多一個聲道就多加一個蜂鳴器或揚聲器。相應新加的播放時左右移就行了。
同樣道理，也能實現和弦等。具體單片機代碼如下：
#include "reg52.h"
unsigned char Count;
sbit _Speak =P3^4 ; //訊響器控制腳
usbit _Speakr =P3^7; //新加訊響器控制腳
nsigned char code SONG[] ={ //祝你平安
0x26,0x20,0x20,0x20,0x20,0x20,0x26,0x10,0x20,0x10,0x20,0x80,0x26,0x20,0x30,0x20,
0x30,0x20,0x39,0x10,0x30,0x10,0x30,0x80,0x26,0x20,0x20,0x20,0x20,0x20,0x1c,0x20,
0x20,0x80,0x2b,0x20,0x26,0x20,0x20,0x20,0x2b,0x10,0x26,0x10,0x2b,0x80,0x26,0x20,
0x30,0x20,0x30,0x20,0x39,0x10,0x26,0x10,0x26,0x60,0x40,0x10,0x39,0x10,0x26,0x20,
0x30,0x20,0x30,0x20,0x39,0x10,0x26,0x10,0x26,0x80,0x26,0x20,0x2b,0x10,0x2b,0x10,
0x2b,0x20,0x30,0x10,0x39,0x10,0x26,0x10,0x2b,0x10,0x2b,0x20,0x2b,0x40,0x40,0x20,
0x20,0x10,0x20,0x10,0x2b,0x10,0x26,0x30,0x30,0x80,0x18,0x20,0x18,0x20,0x26,0x20,
0x20,0x20,0x20,0x40,0x26,0x20,0x2b,0x20,0x30,0x20,0x30,0x20,0x1c,0x20,0x20,0x20,
0x20,0x80,0x1c,0x20,0x1c,0x20,0x1c,0x20,0x30,0x20,0x30,0x60,0x39,0x10,0x30,0x10,
0x20,0x20,0x2b,0x10,0x26,0x10,0x2b,0x10,0x26,0x10,0x26,0x10,0x2b,0x10,0x2b,0x80,
0x18,0x20,0x18,0x20,0x26,0x20,0x20,0x20,0x20,0x60,0x26,0x10,0x2b,0x20,0x30,0x20,
0x30,0x20,0x1c,0x20,0x20,0x20,0x20,0x80,0x26,0x20,0x30,0x10,0x30,0x10,0x30,0x20,
0x39,0x20,0x26,0x10,0x2b,0x10,0x2b,0x20,0x2b,0x40,0x40,0x10,0x40,0x10,0x20,0x10,
0x20,0x10,0x2b,0x10,0x26,0x30,0x30,0x80,0x00,
//路邊的野華不要采
0x30,0x1C,0x10,0x20,0x40,0x1C,0x10,0x18,0x10,0x20,0x10,0x1C,0x10,0x18,0x40,0x1C,
0x20,0x20,0x20,0x1C,0x20,0x18,0x20,0x20,0x80,0xFF,0x20,0x30,0x1C,0x10,0x18,0x20,
0x15,0x20,0x1C,0x20,0x20,0x20,0x26,0x40,0x20,0x20,0x2B,0x20,0x26,0x20,0x20,0x20,
0x30,0x80,0xFF,0x20,0x20,0x1C,0x10,0x18,0x10,0x20,0x20,0x26,0x20,0x2B,0x20,0x30,
0x20,0x2B,0x40,0x20,0x20,0x1C,0x10,0x18,0x10,0x20,0x20,0x26,0x20,0x2B,0x20,0x30,
0x20,0x2B,0x40,0x20,0x30,0x1C,0x10,0x18,0x20,0x15,0x20,0x1C,0x20,0x20,0x20,0x26,
0x40,0x20,0x20,0x2B,0x20,0x26,0x20,0x20,0x20,0x30,0x80,0x20,0x30,0x1C,0x10,0x20,
0x10,0x1C,0x10,0x20,0x20,0x26,0x20,0x2B,0x20,0x30,0x20,0x2B,0x40,0x20,0x15,0x1F,
0x05,0x20,0x10,0x1C,0x10,0x20,0x20,0x26,0x20,0x2B,0x20,0x30,0x20,0x2B,0x40,0x20,
0x30,0x1C,0x10,0x18,0x20,0x15,0x20,0x1C,0x20,0x20,0x20,0x26,0x40,0x20,0x20,0x2B,
0x20,0x26,0x20,0x20,0x20,0x30,0x30,0x20,0x30,0x1C,0x10,0x18,0x40,0x1C,0x20,0x20,
0x20,0x26,0x40,0x13,0x60,0x18,0x20,0x15,0x40,0x13,0x40,0x18,0x80,0x00,
};
void Time0_Init()
{
TMOD = 0x01;
IE = 0x82;
TH0 = 0xD8;
TL0 = 0xEF; //12MZ晶振，10ms
}
void Time0_Int() interrupt 1
{
TH0 = 0xD8;
TL0 = 0xEF;
Count++; //長度加1
}
/*-------------------------------------------------
功能:1MS延時子程序
-------------------------------------------------*/
void Delay_xMs(unsigned int x)
{
unsigned int i,j;
for( i =0;i < x;i++ )
{
for( j =0;j<3;j++ );
}
}
/*-------------------------------------------------
功能:歌曲播放子程序i為播放哪一段曲目
-------------------------------------------------*/
void Play_Song(unsigned char i)
{
unsigned char Temp1,Temp2;
unsigned int Addr;
Count = 0; //中斷計數器清0
Addr = i * 217;
while(1)
{
Temp1 = SONG[Addr++];
if ( Temp1 == 0xFF ) //休止符
{
TR0 = 0;
Delay_xMs(100);
}
else if ( Temp1 == 0x00 ) //歌曲結束符
{
return;
}
else
{
Temp2 = SONG[Addr++];
TR0 = 1;
while(1)
{
_Speak = ~_Speak;
Delay_xMs(Temp1);
if ( Temp2 == Count )
{
Count = 0;
break;
}
//以下為新加的聲道播放
_Speakr = ~_Speakr;//新加的蜂鳴器或揚聲器發聲
Delay_xMs(Temp1>>1);//新加的發音聲道頻率，左移或右移。
if ( Temp2 == Count )
{
Count = 0;
break;
}
}
}
}
/*-------------------------------------------------
功能:主程序
-------------------------------------------------*/
void main()
{
Time0_Init(); //定時器0中斷初始化
while(1)
{
Play_Song(0); //播放
}
}
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