帮忙解答

只看该作者 · 2009-8-27 14:05

#define uint  unsigned int
#define uchar unsigned char
#include <at89x51.h>
unsigned char code sinrom[] =
{
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,
};
//函数的前向声明
uint keydown(void);
uchar keyscan();
void rectangle();
void triangle();
void sin();
void delay1ms(uint k);
void delay10us();
char main()
{
  uchar key;
while(1)
{
  if( keydown())//调用键盘扫描，
  {key=keyscan();
  switch(key)
  {
case 0xfe:
rectangle();
break;
case 0xfd:
triangle();
break;
case 0xfc:
sin();
break;
default:
break;
  }
  }
}
}
//1ms延时函数
void delay1ms(uint k)
{
uint i,j;
for(i=0;i<k;i++)
{
  for(j=0;j<121;j++)
  ;
}
}
//11微秒延时函数
void delay10us(uint t)
{
for(;t>0;t--);
}
uint keydown(void) //判断按键
{
P2=0xf0;
if(P2!=0xf0)
return 1;
else
return 0;
}
uchar keyscan(void)//键盘扫描函数，使用行列反转扫描法
{
uchar cord_h,cord_l;//行列值
P2=0x0f;          //行线输出全为0
cord_h=P2&0x0f;    //读入列线值
if(cord_h!=0x0f) //先检测有无按键按下
{
  delay1ms(100);       //去抖
  if(cord_h!=0x0f)
  {
cord_h=P2&0x0f;  //读入列线值
P2=cord_h|0xf0;  //输出当前列线值
cord_l=P2&0xf0;  //读入行线值
return(cord_h+cord_l);//键盘最后组合码值
}
  }return(0xff);    //返回该值
}

//方波发生函数
void rectangle()
{
P0=0xff;
delay1ms(10);
P0=0x01;
delay1ms(10);
}
//三角波发生函数
void triangle()
{
unsigned char i=0x00;
if(i == 0x00)
{
  for(;i<0xff;i++)
  {
P0=i;
delay10us(100);
  }
}
if(i == 0xff)
{
  for(;i>0;i--)
  {
P0 = i;
delay10us(100);
  }

}
}
//正弦波发生函数
void sin()
{
unsigned char i=0x00;
for(;i<0xff;i++)
{
  P0 = sinrom[i];
  delay10us(100);
}
}

我朋友今天问我一个问题，他说，怎么可以通过改变电阻大小的方式改变各个输出波形的频率，我也是一个初学者，一点设计思路都没有，恳请各位大侠出手相助