相信大家玩过用0832做信号发生器的朋友一定见过下面这个程序，我看到频率的计算时，依据我的理解，信号的频率是根据定时器的时间决定每个点的函数持续时间，比如10hz sin函数 选取的定时是TH0=0XFD,TL0=0X06 (也就是在波频率调整中间值选 waveTH[0]和waveTL[0])
20hz sin函数 选取的定时是TH0=0XFE,TL0=0X8A (也就是在波频率调整中间值选 waveTH[1]和waveTL[1])
。因为sin函数有256个点，所以，定时器定的应该是1/256的周期时间，
。
。但是通过计算我发现用所给的频率调整中间值得出的周期值和预期的不一样，请问我是计算错了还是理解错了？请看以下程序1602显示的相关程序我已经忽略
#include
#define uchar unsigned char
#define uint unsigned int
#define DAdata P0 //DA数据端口
***it 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
***it 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
***it key= P3^2;
uchar wavecount; //'抽点'计数
uchar THtemp,TLtemp;//传递频率的中间变量
//uint T_temp;
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 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 waveTH[]={
0xfd,0xfe,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff, //正弦波频率调整中间值
0xfd,0xfe,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff, //三角波频率调整中间值
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,
0x80,0x88,0x90,0x98,0xa0,0xa8,0xb0,0xb8,0xc0,0xc8,0xd0,0xd8,0xe0,0xe8,0xf0,0xf8,0xff,
0xf8,0xf0,0xe8,0xe0,0xd8,0xd0,0xc8,0xc0,0xb8,0xb0,0xa8,0xa0,0x98,0x90,0x88,0x80,
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
{
DA_S1=0;
DAdata=triangle_tab[wavecount++];
if(wavecount>64) wavecount=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
{
DA_S1=0; //打开8位输入寄存器
DAdata=sine_tab[wavecount++];
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
}
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*/
case 0xb0: //频率按规定单位依次衰减
wavefreq[waveform]--;
if(wavefreq[waveform]<1) wavefreq[waveform]=10; //这边要用“<1”，因为它比“=0”可靠性更高
break;
case 0x70: //TTL输出
DA_S2=1; //使DAC寄存器关闭
break;
}
THtemp=waveTH[waveform*10+(wavefreq[waveform]-1)]; //方括号中选取第几个数后，并把该值赋给T_temp
TLtemp=waveTL[waveform*10+(wavefreq[waveform]-1)];
total_freq= wavefreq[waveform] * freq_unit[waveform]; //求输出频率（个数*单位）
举报
