一，所需元器件

二，电路图

三，代码

#include<reg51.h>

sbit wrd=P3^6;
sbit rdd=P3^2;
sbit key0=P1^0; //定义P1.0脚的按键为正弦波键key0
sbit key1=P1^1; //定义P1.1脚的按键为方波键key1
sbit key2=P1^2; //定义P1.2脚的按键为三角波键key2
sbit key3=P1^3; //定义P1.3脚的按键为梯形波键key3
sbit key4=P1^4; //定义P1.3脚的按键为锯齿波键key4
unsigned char flag; //flag为1、2、3、4、5时对应
//正弦波、方波、三角波、梯形波、锯齿波
unsigned char const code //以下为正弦波采样点数组256个数据
SIN_code[256]={0x80,0x83,0x86,0x89,0x8c,0x8f,0x92,0x95,0x98,0x9c,0x9f,0xa2,0xa5,0xa8,0xab,0xae,
0xb0,0xb3,0xb6,0xb9,0xbc,0xbf,0xc1,0xc4,0xc7,0xc9,0xcc,0xce,0xd1,0xd3,0xd5,0xd8,0xda,0xdc,0xde,0xe0,0xe2,
0xe4,0xe6,0xe8,0xea,0xec,0xed,0xef,0xf0,0xf2,0xf3,0xf4,0xf6,0xf7,0xf8,0xf9,0xfa,0xfb,0xfc,0xfc,0xfd,0xfe,0xfe,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xfe,0xfe,0xfd,0xfc,0xfc,0xfb,0xfa,0xf9,0xf8,0xf7,0xf6,
0xf5,0xf3,0xf2,0xf0,0xef,0xed,0xec,0xea,0xe8,0xe6,0xe4,0xe3,0xe1,0xde,0xdc,0xda,0xd8,0xd6,0xd3,0xd1,0xce,0xcc,
0xc9,0xc7,0xc4,0xc1,0xbf,0xbc,0xb9,0xb6,0xb4,0xb1,0xae,0xab,0xa8,0xa5,0xa2,0x9f,0x9c,0x99,0x96,0x92,0x8f,0x8c,
0x89,0x86,0x83,0x80,0x7d,0x79,0x76,0x73,0x70,0x6d,0x6a,0x67,0x64,0x61,0x5e,0x5b,0x58,0x55,0x52,0x4f,0x4c,0x49,
0x46,0x43,0x41,0x3e,0x3b,0x39,0x36,0x33,0x31,0x2e,0x2c,0x2a,0x27,0x25,0x23,0x21,0x1f,0x1d,0x1b,0x19,0x17,0x15,
0x14,0x12,0x10,0xf,0xd,0xc,0xb,0x9,0x8,0x7,0x6,0x5,0x4,0x3,0x3,0x2,0x1,0x1,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,0x0,
0x0,0x0,0x1,0x1,0x2,0x3,0x3,0x4,0x5,0x6,0x7,0x8,0x9,0xa,0xc,0xd,0xe,0x10,0x12,0x13,0x15,0x17,0x18,0x1a,
0x1c,0x1e,0x20,0x23,0x25,0x27,0x29,0x2c,0x2e,0x30,0x33,0x35,0x38,0x3b,0x3d,0x40,0x43,0x46,0x48,0x4b,0x4e,0x51,
0x54,0x57,0x5a,0x5d,0x60,0x63,0x66,0x69,0x6c,0x6f,0x73,0x76,0x79,0x7c};

unsigned char keyscan();
void init_DA0832();
void SIN();
void square();
void triangle();
void sawtooth();
void trapezoidal();

void main()
{
init_DA0832(); // DA0832的初始化函数
do {
flag=keyscan(); //将键盘扫描函数得到的键值赋给flag
}while(!flag);
while(1)
{

switch(flag)
{
case 1:
do{
flag=keyscan();
SIN();
}while(flag==1);
break;
case 2:
square ();
do{
flag=keyscan();
}while(flag==2);
TR0=0;
break;
case 3:
do{
flag=keyscan();
triangle ();
}while(flag==3);
break;
case 4:
do{
flag=keyscan();
trapezoidal ();
}while(flag==4);
break;
case 5:
do{
flag=keyscan();
sawtooth ();
}while(flag==5);
break;
default:
flag=keyscan();
break;
}
}
}

unsigned char keyscan()
{
unsigned char keyscan_num,temp;
P1=0xff; // P1口输入
temp=P1; //从P1口读入键值，存入temp中
//判是否有键按下，即键值不为0xff，则有键按下
if(~(temp&0xff))
{
if(key0==0) //产生正弦波的按键按下，P1.0=0
{
keyscan_num=1; //得到的键值为1，表示产生正弦波
}
else if(key1==0) //产生方波的按键按下，P1.1=0
{
keyscan_num=2; //得到键值为2，表示产生方波
}
else if(key2==0)
{ //产生三角波的按键按下， P1.2=0
keyscan_num=3; //得到的键值为3，表示产生三角波
}
else if(key3==0)
{ //产生梯形波的按键按下，P1.3=0
keyscan_num=4; //得到的键值为4，表示产生梯形波
}
else if(key4==0)
{ //产生锯齿波的按键按下， P1.3=0
keyscan_num=5; //得到的键值为5，表示产生锯齿波
}
else
{
keyscan_num=0; //没有按键按下，键值为0
}
//得到的键值返回
}
return keyscan_num; // ############################
}

void init_DA0832()
{
rdd=0;
wrd=0;
}
void SIN()
{ //正弦波函数
unsigned int i;
do{
P2=SIN_code[i]; //由P2口输出给DAC0832正弦波数据
i=i+1; //数组数据指针增1
}while(i<256); //判是否已输出完256个波形数据，
i=0; //未完继续输出数据 #############################
}

void square()
{ //方波函数
EA=1; //总中断允许
ET0=1; //允许T0中断
TMOD=1; //T0工作在方式1
TH0=0xff; //给T0高8位装入时间常数
TL0=0x83; //给T0低8位装入时间常数
TR0=1; //启动T0
}

void triangle()
{ //三角波函数
P2=0x00; //三角波函数初始值为0
do{
P2=P2+1; //三角波上升沿
}while(P2<0xff); //判是否已经输出为0xff
P2=0xff;
do{
P2=P2-1; //三角波下降沿
}while(P2>0x00); //判是否已经输出为0
P2=0x00;
}

void sawtooth()
{ //锯齿波函数
P2=0x00;
do{
P2=P2+1; //产生锯齿波的上升沿
}while(P2<0xff); //判上升沿是否已经 结束
}

void trapezoidal()

{ //梯形波函数

unsigned char i;

P2=0x00;

do{

P2=P2+1;

//产生梯形波的上升沿

}while(P2<0xff);

P2=0xff;

//产生梯形波的平顶

for(i=255;i>0;i--)

{ //梯形波的平顶延时
P2=0xff; //产生梯形波的下降沿
} do{
P2=P2-1; //产生梯形波的下降沿
}while(P2>0x00); //判梯形波的下降沿是否结束
P2=0x00;
}

void timer0(void) interrupt 1//定时器T0的中断函数
{
P2=~P2; //方波的输出电平求反
TH0=0xff; //重装定时时间常数
TL0=0x83;
TR0=1; //启动定时器T0
}

后面注释#########部分与课本不同，分别修改了，编译过程中，返回值警告；信号输出过程中无法产生连续正弦波的问题。