单片机C51产生正弦波可控制周期（通过计时器）

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使用软件keli和proteus

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代码如下（示例）：

#include
#define uchar unsigned char 
#define uint unsigned int
sbit P1_0=P1^0;
sbit P1_1=P1^1;
sbit P1_2=P1^2;
sbit P1_3=P1^3;
sbit P2_4=P2^4;
sbit P2_5=P2^5;
sbit P2_6=P2^6;
sbit P2_7=P2^7;
uchar code sin[256]={0x80,0x83,0x86,0x89,0x8d,0x90,0x93,0x96,0x99,0x9c,0x9f,
0xa2,0xa5,0xa8,0xab,0xae,0xb1,0xb4,0xb7,0xba,0xbc,0xbf,0xc2,0xc5,0xc7,
0xca,0xcc,0xcf,0xd1,0xd4,0xd6,0xd8,0xda,0xdd,0xdf,0xe1,0xe3,0xe5,0xe7,
0xe9,0xea,0xec,0xee,0xef,0xf1,0xf2,0xf4,0xf5,0xf6,0xf7,0xf8,0xf9,0xfa,
0xfb,0xfc,0xfd,0xfd,0xfe,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xfe,0xfd,0xfd,0xfc,0xfb,0xfa,0xf9,0xf8,0xf7,
0xf6,0xf5,0xf4,0xf2,0xf1,0xef,0xee,0xec,0xea,0xe9,0xe7,0xe5,0xe3,0xe1,0xde,0xdd,
0xda,0xd8,0xd6,0xd4,0xd1,0xcf,0xcc,0xca,0xc7,0xc5,0xc2,0xbf,0xbc,0xba,
0xb7,0xb4,0xb1,0xae,0xab,0xa8,0xa5,0xa2,0x9f,0x9c,0x99,0x96,0x93,0x90,
0x8d,0x89,0x86,0x83,0x80,
0x80,0x7c,0x79,0x76,0x72,0x6f,0x6c,0x69,0x66,0x63,0x60,0x5d,0x5a,0x57,0x55,0x51,
0x4e,0x4c,0x48,0x45,0x43,0x40,0x3d,
0x3a,0x38,0x35,0x33,0x30,0x2e,0x2b,0x29,0x27,0x25,0x22,0x20,0x1e,0x1c,
0x1a,0x18,0x16,0x15,0x13,0x11,0x10,0x0e,0x0d,0x0b,0x0a,0x09,0x08,0x07,
0x06,0x05,0x04,0x03,0x02,0x02,0x01,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x02,0x02,0x03,0x04,0x05,0x06,0x07,0x08,
0x09,0x0a,0x0b,0x0d,0x0e,0x10,0x11,0x13,0x15,0x16,0x18,0x1a,0x1c,0x1e,
0x20,0x22,0x25,0x27,0x29,0x2b,0x2e,0x30,0x33,0x35,0x38,0x3a,0x3d,0x40,
0x43,0x45,0x48,0x4c,0x4e,0x51,0x55,0x57,0x5a,0x5d,0x60,0x63,0x66,0x69,
0x6c,0x6f,0x72,0x76,0x79,0x7c,0x80};  //???
uchar a=0,k=20;
uint flag=1,changeflag=1;
void delay(uint x)
{
	uint i;uint j;
	for(j=0;j
	TMOD=0x02;
	TH0=0xb2;//78us
	TL0=0xb2;
	EA=1;
	ET0=1;
	TR0=0;
}
void main(void)
{
	uint i=0;	uint count=5;
	Inittimer();
		while(1)
	{
	if(P0!=0xff)
	{
			if(P1_0==0){TR0=1;}//¿ª
			if(P1_1==0){TR0=0;}//¹Ø
			if(P1_2==0){delay(1500);if(P1_2==0&&count<9){count++;}}//µ÷´óƵÂÊ
			if(P1_3==0){delay(1500);if(P1_3==0&&count>1){count--;}}//µ÷СƵÂÊ
			switch(count)
			{
				case 1:k=100;P2=0xfe;break;//10hz
				case 2:k=50;P2=0xfd;break;//20hz
				case 3:k=33;P2=0xfb;break;//30hz
				case 4:k=25;P2=0xf7;break;//40hz
				case 5:k=20;break;//50hz
				case 6:k=16;P2=0xef;break;//60hz
				case 7:k=14;P2=0xdf;break;//70hz
				case 8:k=12;P2=0xbf;break;//80hz
				case 9:k=11;P2=0x7f;break;//90hz
			}	
			
	}
	if(i==256)i=0;
	while(flag){P0=sin[i];i++;flag=0;}
}
}
void timer0() interrupt 1//定时器0中断函数
{	
	a++;
	if(a==k){flag=1;a=0;}
}

• 第一点

（如果有大佬知道的，望纠正！）

proteus的时钟频率必须为240MHz，因为经过实测当时钟周期在12MHz的时候无论怎么怎么减少计数值都维持在一定数值。初步判断好像是因为时钟频率的瓶颈，编者只能通过增大时钟频率来将正弦函数的周期维持在1ms，而通过中断函数中参数进行累加的方式来调整时钟的周期（降低误差）。以下是编者测量定时器与正弦函数周期的一些过程值，仅供读者参考：
采用定时器方式2，8位自动重置定时计数器方式
TMOD=0x02；
64当初值为100，计数值156，周期为40ms
f6当初值为246，计数值10，出错无法正常显示正弦信号
ec当初值为236，计数值为20，出错
e2当初值为226，计数值为30，14ms
c8当初值为200，计数值为56，14ms
还有在定时器0工作在方式1时候的数据，我觉还需要核实一下就不放出来了。

• 第二点

由于对时钟周期进行改变，导致对延迟函数会有影响，需要增大原来的延迟数这里1500是编者粗略的计算。

就是通过即使定时器不断的修改标志位flag，从而让数组sin每隔一定的时间对P0口进行赋值，进而通过数模转换器进行模拟量的输出。进而输入到示波器。

关于上面的第一点编者还存在疑惑，有大佬知道，望能告知！！
有人与需要电路图和hex文件私信！！
初次发稿，有错误望能指正！！