系统框图
该系统采用单片机作为数据处理及控制核心，由单片机完成人机界面、系统控制、信号的采集分析以及信号的处理和变换，采用按键输入，利用虚拟示波器显示波形的方案。将设计任务分解为按键电路、输出转换电路等模块。图3-2为系统的总体框图。
 
 
系统仿真
单击仿真界面左下方的开始按扭，仿真就开始了。具体仿真过程如下：
（1）f=50HZ正弦波的调试结果
 

单片机源程序如下:

#include

#define  uchar unsigned char

#define  uint  unsigned int

#define DAdata  P0        //DA数据端口

sbit DA_S1= P2^0;   // 控制DAC0832的8位输入寄存器，仅当都为0时，可以输出数据(处于直通状态)，否则，输出将被锁存

sbit DA_S2= P2^1;   // 控制DAC0832的8位DAC寄存器，仅当都为0时，可以输出数据(处于直通状态)，否则，输出将被锁存

sbit key=   P3^2;

uchar wavecount;    //'抽点'计数

uchar THtemp,TLtemp;//传递频率的中间变量

uchar judge=1;      //在方波输出函数中用于简单判别作用

uchar waveform;            //当其为0、1、2时，分别代表三种波

uchar code freq_unit[3]={10,50,200}; //三种波的频率单位

uchar idata wavefreq[3]={1,1,1};           //给每种波定义一个数组单元，用于存放单位频率的个数

uchar code  lcd_hang1[]={"Sine Wave       " "Triangle Wave   " "Square Wave     " "Select Wave:    " "press No.1 key! "};

uchar idata lcd_hang2[16]={"f=    Hz        "};

uchar code waveTH[]={

    0xfd,0xfe,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,

0xfd,0xfe,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,

0xec,0xf6,0xf9,0xfb,0xfc,0xfc,0xfd,0xfd,0xfd,0xfe};

uchar code waveTL[]={ 

    0x06,0x8a,0x10,0x4e,0x78,0x93,0xa8,0xb3,0xbe,0xc6, //正弦波频率调整中间值

0xac,0xde,0x48,0x7a,0x99,0xaf,0xbb,0xc8,0xd0,0xde,        //三角波频率调整中间值

0x88,0x50,0x90,0x32,0x34,0xbe,0x4a,0xa3,0xe5,0x2c}; 

/*************************************************************************************************/

uchar code triangle_tab[]={         //每隔数字8，采取一次

0x00,0x08,0x10,0x18,0x20,0x28,0x30,0x38,0x40,0x48,0x50,0x58,0x60,0x68,0x70,0x78,

0x80,0x88,0x90,0x98,0,0xa8,0xb0,0xb8,0xc0,0xc8,0xd0,0xd8,0xe0,0xe8,0xf0,0xf8,0xff,

0xf8,0xf0,0xe8,0xe0,0xd8,0xd0,0xc8,0xc0,0xb8,0xb0,0xa8,0,0x98,0x90,0x88,0x80,

0x78,0x70,0x68,0x60,0x58,0x50,0x48,0x40,0x38,0x30,0x28,0x20,0x18,0x10,0x08,0x00};

uchar code sine_tab[256]={

//输出电压从0到最大值（正弦波1/4部分）

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,

//输出电压从最大值到0（正弦波1/4部分）

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,

//输出电压从0到最小值（正弦波1/4部分）

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,

//输出电压从最小值到0（正弦波1/4部分）

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}; 

void delay(uchar z)          

{

    uint x,y;

for(x=z;x>0;x--)

for(y=110;y>0;y--);

}

void triangle_out()        //三角波输出

{

    DAdata=triangle_tab[wavecount++];

if(wavecount>64) wavecount=0;

DA_S1=0;  //打开8位输入寄存器

DA_S1=1;  //关闭8位输入寄存器

}

void sine_out()         //正弦波输出

{

    DAdata=sine_tab[wavecount++];

DA_S1=0;  //打开8位输入寄存器

DA_S1=1;  //关闭8位输入寄存器

}

void square_out()  //方波输出

{

    judge=~judge;

    if(judge==1) DAdata=0xff;

else  DAdata=0x00;

DA_S1=0;  //打开8位输入寄存器

DA_S1=1;  //关闭8位输入寄存器

}

/************1602液晶的相关函数*************/

#define lcd_ports P1

sbit rs=P2^2;

sbit rw=P2^3;

sbit lcden=P2^4;

void write_com(uchar com)

{

rs=0;        //置零，表示写指令

lcden=0;

lcd_ports=com;

delay(5);

lcden=1;

delay(5);

lcden=0;

}

void write_date(uchar date)

{

rs=1;        //置1，表示写数据（在指令所指的地方写数据）

lcden=0;

lcd_ports=date;

delay(5);

lcden=1;

delay(5);

lcden=0;

}

void disp_lcd(uchar addr,uchar *temp1)

{

uchar num;

write_com(addr);

delay(1);   //延时一会儿???

for(num=0;num<16;num++)

{

write_date(temp1[num]);//或者这样写write_date(*(temp1+num));

delay(1);

}

}

void init_lcd()

{

//uchar num;

lcden=0;  //可有可无???

rw=0;  //初始化一定要设置为零，表示写数据

write_com(0x38);  //使液晶显示点阵，为下面做准备

write_com(0x0c);  //初始设置

write_com(0x06);  //初始设置

write_com(0x01);  //清零

write_com(0x80);  //使指针指向第一行第一格

    disp_lcd(0x80,&lcd_hang1[3*16]);  //在第一行显示

    disp_lcd(0xc0,&lcd_hang1[4*16]);  //在第二行显示

}

/********************1602液晶函数声明结束*********************/

void main()

{

    uchar i=0;

DA_S2=0;    //使DAC寄存器处于直通状态

DAdata=0;

DA_S1=1;    //关闭8位输入寄存器

init_lcd();

    waveform=0;

TMOD=0x01;  //设置定时器0为16位工作方式

IT0=1;      //设置外部中断0为下降沿触发

ET0=1;      //开定时器中断

EX0=1; 

EA=1;

while(1)

{

//DAout(0xff);           //可输出TTL波形

//DAout(0x80);

//T_temp=32;

}

}         

void timer0() interrupt 1

{

TH0=THtemp;

TL0=TLtemp;

if(waveform==0)      sine_out();

else if(waveform==1) triangle_out();

else if(waveform==2) square_out();

}

void key_int0() interrupt 0

{

    uchar keytemp;

uint total_freq; //总频率

EA=0; TR0=0;     //关总中断与定时器

delay(5);       //延时够吗???

if(key==0)       //确实有按键按下而引发中断

{

keytemp=P3&0xf0; //获取P3口高四位的值

switch(keytemp)

{

    case 0xe0:        //选择波形

     waveform++;

if(waveform>2) waveform=0;

break;

    case 0xd0:  //频率按规定单位依次增加

     wavefreq[waveform]++;

if(wavefreq[waveform]>10) wavefreq[waveform]=1; // /*这边要用“>10”，因为它比“=11”可靠

break;         //   性更高,使加数有个上限，不会一直加下去*/

……………………