51单片机用矩阵按键控制无源蜂鸣器发Do Re Mi Fa So La Si Do,用定时器实现代码

以下是51单片机使用矩阵按键控制无源蜂鸣器发Do Re Mi Fa So La Si Do的示例代码，使用定时器实现：

#include <reg52.h>

#define uchar unsigned char
#define uint unsigned int

uchar code DO = 0x3f;
uchar code RE = 0x5f;
uchar code MI = 0x6f;
uchar code FA = 0x77;
uchar code SO = 0x7b;
uchar code LA = 0x7d;
uchar code SI = 0x7e;

uchar code Keytable[] = {0xee, 0xde, 0xbe, 0x7e, 0xed, 0xdd, 0xbd, 0x7d, 0xeb, 0xdb, 0xbb, 0x7b, 0xe7, 0xd7, 0xb7, 0x77};

uchar code Tone[] = {DO, RE, MI, FA, SO, LA, SI, DO};

uchar music = 0xff;
uchar keyvalue = 0xff;

void delay(uint z)
{
    uint x,y;
    for(x=z;x>0;x--)
        for(y=110;y>0;y--);
}

void keyscan()
{
    uchar i;
    P1 = 0x0f;
    if(P1 != 0x0f)
    {
        delay(10);
        if(P1 != 0x0f)
        {
            P1 = 0x0f;
            keyvalue = P1;
            P1 |= 0xf0;
            keyvalue |= P1;
            for(i=0;i<16;i++)
            {
                if(keyvalue == Keytable[i])
                {
                    music = i;
                    break;
                }
            }
        }
    }
}

void tm0() interrupt 1
{
    TH0 = (65536-5000)/256;
    TL0 = (65536-5000)%256;
    P2 = Tone[music];
}

void main()
{
    TMOD = 0x01;
    TH0 = (65536-5000)/256;
    TL0 = (65536-5000)%256;
    EA = 1;
    ET0 = 1;
    TR0 = 1;
    while(1)
    {
        keyscan();
        if(music != 0xff)
        {
            TR0 = 0;
            TH0 = (65536-5000)/256;
            TL0 = (65536-5000)%256;
            TR0 = 1;
        }
    }
}

在此示例代码中，`Keytable`数组存储了矩阵按键的扫描码，`Tone`数组存储了发声的频率。`keyscan()`函数用于扫描矩阵按键，若检测到有按键按下，则根据按下的键值设置`music`变量的值。`tm0()`函数为定时器0的中断服务程序，每次中断时将`Tone[music]`输出到P2口，从而使蜂鸣器发声。主函数中不断调用`keyscan()`函数进行按键扫描，并根据按键设置`music`变量的值。若`music`变量不为0xff，则表示有按键按下，此时停止定时器0的计数，重新设置计数值，然后再次启动计数，从而使蜂鸣器发出对应的音符。