此例程設(shè)置了按鍵可以調(diào)整100-1000hz的不同頻率（100的倍數(shù)）的方波，另外還加入了串口通信，可以通過串口發(fā)送來的數(shù)字來設(shè)置相對應(yīng)的頻率；

#include

#include"uart.h"

sbit PWMOUT = P1^0;

sbit led = P2^2;

sbit KEY1 = P1^2;

sbit KEY2 = P3^3;

unsigned char HighRH = 0; //高電平重載值的高字節(jié)

unsigned char HighRL = 0; //高電平重載值的低字節(jié)

unsigned char LowRH = 0; //低電平重載值的高字節(jié)

unsigned char LowRL = 0; //低電平重載值的低字節(jié)

unsigned int fr;

unsigned int k=0,t,i;

unsigned int s= 100;

unsigned char a[3];

unsigned int b=0;

void ConfigPWM(unsigned int fr, unsigned char dc);

void ConfigUART(unsigned int baud);

void delay(unsigned int n){ while (n--);}

void main()

{

bit backup1 = 1;

bit backup2 = 1;

bit keybuf1 = 1; //按鍵值暫存，臨時保存按鍵的掃描值

bit keybuf2 = 1; //按鍵值暫存，臨時保存按鍵的掃描值

//keybuf1 = KEY1; //把當(dāng)前掃描值暫存

EA=1;

led = 0;

ConfigUART(9600); //配置波特率為9600

ConfigPWM(100,50);

//Timer1Init();

while (1)

{

if(k==1)

{

k=0;

ConfigPWM(s,50);

led = ~led;delay(2000);

}

keybuf1 = KEY1; //把當(dāng)前掃描值暫存

if (keybuf1 != backup1) //當(dāng)前值與前次值不相等說明此時按鍵有動作

{

delay(1000); //延時大約10ms

if (keybuf1 == KEY1) //判斷掃描值有沒有發(fā)生改變，即按鍵抖動

{

if (backup1 == 0) //如果前次值為0，則說明當(dāng)前是彈起動作

{

s = s-50;

}

backup1 = keybuf1; //更新備份為當(dāng)前值，以備進行下次比較

}

ConfigPWM(s,50);

}

keybuf2 = KEY2; //把當(dāng)前掃描值暫存

if (keybuf2 != backup2) //當(dāng)前值與前次值不相等說明此時按鍵有動作

{

delay(1000); //延時大約10ms

if (keybuf2 == KEY2) //判斷掃描值有沒有發(fā)生改變，即按鍵抖動

{

if (backup2 == 0) //如果前次值為0，則說明當(dāng)前是彈起動作

{

s = s+50;

}

backup2 = keybuf2; //更新備份為當(dāng)前值，以備進行下次比較

}

ConfigPWM(s,50);

}

}

}

void ConfigUART(unsigned int baud)

{

SCON = 0x50; //配置串口為模式1

TMOD &= 0x0F; //清零T1的控制位

TMOD |= 0x20; //配置T1為模式2

TH1 = 256 - (11059200/12/32)/baud; //計算T1重載值

TL1 = TH1; //初值等于重載值

ET1 = 0; //中斷T1

ES = 1; //串口中斷

TR1 = 1; //啟動T1

}

void ConfigPWM(unsigned int fr, unsigned char dc)

{

unsigned int high, low;

unsigned long tmp;

tmp = (11059200/12)/fr; //計算一個周期所需的計數(shù)值

high = (tmp*dc) / 100; //計算高電平所需的計數(shù)值

low = tmp - high; //計算低電平所需的計數(shù)值

high = 65536 - high + 12; //計算高電平的重載值并補償中斷延時

low = 65536 - low + 12; //計算低電平的重載值并補償中斷延時

HighRH = (unsigned char)(high>>8); //高電平重載值拆分為高低字節(jié)

HighRL = (unsigned char)high;

LowRH = (unsigned char)(low>>8); //低電平重載值拆分為高低字節(jié)

LowRL = (unsigned char)low;

TMOD &= 0xF0; //清零 T0 的控制位

TMOD |= 0x01; //配置 T0 為模式 1

TH0 = HighRH; //加載 T0 重載值

TL0 = HighRL;

ET0 = 1; //使能 T0 中斷

TR0 = 1; //啟動 T0

PWMOUT = 1; //輸出高電平

}

void InterruptTimer0() interrupt 1

{

if (PWMOUT == 1) //當(dāng)前輸出為高電平時，裝載低電平值并輸出低電平

{

TH0 = LowRH;

TL0 = LowRL;

PWMOUT = 0;

}

else //當(dāng)前輸出為低電平時，裝載高電平值并輸出高電平

{

TH0 = HighRH;

TL0 = HighRL;

PWMOUT = 1;

}

}

/*void Timer1Init()

{

TMOD|=0X10;//選擇為定時器1模式，工作方式1，僅用TR1打開啟動。

TH1=0XFC; //給定時器賦初值，定時1ms

TL1=0X18;

ET1=1;//打開定時器1中斷允許

EA=1;//打開總中斷

TR1=1;//打開定時器

}

void Timer1() interrupt 3

{

static u16;

TH1=0XFC; //給定時器賦初值，定時1ms

TL1=0X18;

i++;

if(i==1000)

{

i=0;

t++;

if(t%2==0)

{

SBUF=t/10;

SBUF=t%10;

}

}

}*/

void ComINT() interrupt 4 //中斷接收程序

{

if(RI) //判斷是否接收完，接收完成后，由硬件置RI位

{

RI=0;

//SBUF=SBUF;

a[b]=SBUF;

b++;

if(b==3)

{

/*if(a[0]=='a'&&a[1]=='b'&&a[2]=='c')

{led = 0;delay(2000);}

else

{led = 1;}*/

b=0;s=(a[0]-0x30)*100+(a[1]-0x30)*10+(a[2]-0x30);

k=1;

//SBUF = 'T';

}

}

if(TI)

{

TI=0;

}

}