蜂鸣器

控制蜂鸣器的发声频率 ，让其发出不同种声音

#include <reg52.h>


sbit pwm = P1^3;


unsigned char T0RH = 0;
unsigned char T0RL = 0;
unsigned int i;


void OpenPwm (unsigned int frequ);
void StopPwm ();


void main()
{
  EA = 1;        //打开中断
  TMOD = 0x01;//打开定时器
       
       
       
        while(1)
        {
          OpenPwm(4000);//设置频率
                for(i=0;i<40000;i++);
                StopPwm();
                for(i=0;i<2000;i++);
          OpenPwm(1000);
                for(i=0;i<40000;i++);
                StopPwm();
                for(i=0;i<40000;i++);




        }
}


void OpenPwm (unsigned int frequ)
{
unsigned int reload;
       
        reload = 65536 -(12000000/12)/(frequ*2);//计算溢出
        T0RH = (unsigned char) (reload>>8);
        T0RL = (unsigned char) reload;
        TH0 = 0xFE;
        TL0 = 0xFE;
        ET0 = 1;
        TR0 = 1;
}
void StopPwm()
{
  ET0 = 0;
        TR0 = 0;
}


void InterruptTimer0() interrupt 1
{
  TH0 = T0RH;
        TL0 = T0RL;
        pwm = ~pwm;
}