📄 ds18b20数字温度计使用.htm
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<P style="TEXT-ALIGN: center" align=center>名称</P></TD>
<TD
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<P style="TEXT-ALIGN: center"
align=center>引脚功能描述</P></TD></TR>
<TR>
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<P>1</P></TD>
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<P>GND</P></TD>
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<P>地信号</P></TD></TR>
<TR>
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<P>2</P></TD>
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<P>DQ</P></TD>
<TD
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<P>数据输入/输出引脚。开漏单总线接口引脚。当被用着在寄生电源下，也可以向器件提供电源。</P></TD></TR>
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<P>3</P></TD>
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<P>VDD</P></TD>
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<P>可选择的VDD引脚。当工作于寄生电源时，此引脚必须接地。</P></TD></TR></TBODY></TABLE>
<P
style="MARGIN-LEFT: 39pt; TEXT-INDENT: -39pt; tab-stops: list 39.0pt left 54.0pt; mso-list: l0 level2 lfo1">3．
DS18B20的使用方法
<P
style="TEXT-INDENT: 21pt; tab-stops: 54.0pt">由于DS18B20采用的是1－Wire总线协议方式，即在一根数据线实现数据的双向传输，而对AT89S51单片机来说，硬件上并不支持单总线协议，因此，我们必须采用软件的方法来模拟单总线的协议时序来完成对DS18B20芯片的访问。
<P
style="TEXT-INDENT: 21pt; tab-stops: 54.0pt">由于DS18B20是在一根I/O线上读写数据，因此，对读写的数据位有着严格的时序要求。DS18B20有严格的通信协议来保证各位数据传输的正确性和完整性。该协议定义了几种信号的时序：初始化时序、读时序、写时序。所有时序都是将主机作为主设备，单总线器件作为从设备。而每一次命令和数据的传输都是从主机主动启动写时序开始，如果要求单总线器件回送数据，在进行写命令后，主机需启动读时序完成数据接收。数据和命令的传输都是低位在先。
<P style="TEXT-INDENT: 21pt; tab-stops: 54.0pt">DS18B20的复位时序
<P style="tab-stops: 54.0pt"><IMG height=142
src="DS18B20数字温度计使用.files/200692185725580.gif" width=544
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<P>DS18B20的读时序
<P
style="TEXT-INDENT: 21pt; tab-stops: 54.0pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt">对于DS18B20的读时序分为读0时序和读1时序两个过程。
<P
style="TEXT-INDENT: 21pt; tab-stops: 54.0pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt">对于DS18B20的读时隙是从主机把单总线拉低之后，在15秒之内就得释放单总线，以让DS18B20把数据传输到单总线上。DS18B20在完成一个读时序过程，至少需要60us才能完成。
<P style="tab-stops: 54.0pt"><IMG height=152
src="DS18B20数字温度计使用.files/200692185726621.gif" width=544
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<P style="tab-stops: 54.0pt">DS18B20的写时序
<P
style="TEXT-INDENT: 21pt; tab-stops: 54.0pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt">对于DS18B20的写时序仍然分为写0时序和写1时序两个过程。
<P
style="TEXT-INDENT: 21pt; tab-stops: 54.0pt; mso-char-indent-count: 2.0; mso-char-indent-size: 10.5pt">对于DS18B20写0时序和写1时序的要求不同，当要写0时序时，单总线要被拉低至少60us，保证DS18B20能够在15us到45us之间能够正确地采样IO总线上的“0”电平，当要写1时序时，单总线被拉低之后，在15us之内就得释放单总线。
<P style="tab-stops: 54.0pt"><IMG height=168
src="DS18B20数字温度计使用.files/200692185726360.gif" width=544
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<P
style="MARGIN-LEFT: 39pt; TEXT-INDENT: -39pt; tab-stops: list 39.0pt left 54.0pt; mso-list: l0 level2 lfo1">4．
实验任务
<P
style="TEXT-INDENT: 21pt; tab-stops: 54.0pt">用一片DS18B20构成测温系统，测量的温度精度达到0.1度，测量的温度的范围在－20度到＋100度之间，用8位数码管显示出来。
<P
style="MARGIN-LEFT: 36pt; TEXT-INDENT: -36pt; tab-stops: list 36.0pt left 54.0pt; mso-list: l5 level1 lfo8">5．
电路原理图
<P style="tab-stops: 54.0pt"><IMG height=564
src="DS18B20数字温度计使用.files/200692185726371.gif" width=544
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<P style="tab-stops: 54.0pt">
<P
style="MARGIN-LEFT: 36pt; TEXT-INDENT: -36pt; tab-stops: list 36.0pt left 54.0pt; mso-list: l5 level1 lfo8">6．
系统板上硬件连线
<P
style="MARGIN-LEFT: 70.3pt; TEXT-INDENT: -49.3pt; tab-stops: list 0cm left 54.0pt; mso-list: l4 level1 lfo3">（1）．
把“单片机系统”区域中的P0.0－P0.7用8芯排线连接到“动态数码显示”区域中的ABCDEFGH端子上。
<P
style="MARGIN-LEFT: 70.3pt; TEXT-INDENT: -49.3pt; tab-stops: list 0cm left 54.0pt; mso-list: l4 level1 lfo3">（2）．
把“单片机系统”区域中的P2.0－P2.7用8芯排线连接到“动态数码显示”区域中的S1S2S3S4S5S6S7S8端子上。
<P
style="MARGIN-LEFT: 70.3pt; TEXT-INDENT: -49.3pt; tab-stops: list 0cm left 54.0pt; mso-list: l4 level1 lfo3">（3）．
把DS18B20芯片插入“四路单总线”区域中的任一个插座中，注意电源与地信号不要接反。
<P
style="MARGIN-LEFT: 70.3pt; TEXT-INDENT: -49.3pt; tab-stops: list 0cm left 54.0pt; mso-list: l4 level1 lfo3">（4）．
把“四路单总线”区域中的对应的DQ端子连接到“单片机系统”区域中的P3.7/RD端子上。
<P
style="MARGIN-LEFT: 36pt; TEXT-INDENT: -36pt; tab-stops: list 36.0pt left 54.0pt; mso-list: l5 level1 lfo8">7．
C语言源程序<BR>#include <AT89X52.H><BR>#include
<INTRINS.h><BR> <BR>unsigned char code
displaybit[]={0xfe,0xfd,0xfb,0xf7,<BR>0xef,0xdf,0xbf,0x7f};<BR>unsigned
char code
displaycode[]={0x3f,0x06,0x5b,0x4f,<BR>0x66,0x6d,0x7d,0x07,<BR>0x7f,0x6f,0x77,0x7c,<BR>0x39,0x5e,0x79,0x71,0x00,0x40};<BR>unsigned
char code
dotcode[32]={0,3,6,9,12,16,19,22,<BR>25,28,31,34,38,41,44,48,<BR>50,53,56,59,63,66,69,72,<BR>75,78,81,84,88,91,94,97};<BR>unsigned
char displaycount;<BR>unsigned char
displaybuf[8]={16,16,16,16,16,16,16,16};<BR>unsigned char
timecount;<BR>unsigned char readdata[8]; <BR>sbit
DQ=P3^7;<BR>bit sflag;<BR> <BR>bit
resetpulse(void)<BR>{<BR>unsigned char
i;<BR> <BR>DQ=0;<BR>for(i=255;i>0;i--);<BR>DQ=1;<BR>for(i=60;i>0;i--);<BR>return(DQ);<BR>for(i=200;i>0;i--);<BR>}<BR> <BR>void
writecommandtods18b20(unsigned char command)<BR>{<BR>unsigned
char i;<BR>unsigned char
j;<BR> <BR>for(i=0;i<8;i++)<BR>{<BR>if((command &
0x01)==0)<BR>{<BR>DQ=0;<BR>for(j=35;j>0;j--);<BR>DQ=1;<BR>}<BR>else<BR>{<BR>DQ=0;<BR>for(j=2;j>0;j--);<BR>DQ=1;<BR>for(j=33;j>0;j--);<BR>}<BR>command=_cror_(command,1);<BR>}<BR>}<BR> <BR>unsigned
char readdatafromds18b20(void)<BR>{<BR>unsigned char
i;<BR>unsigned char j;<BR>unsigned char
temp;<BR> <BR>temp=0;<BR>for(i=0;i<8;i++)<BR>{<BR>temp=_cror_(temp,1);<BR>DQ=0;<BR>_nop_();<BR>_nop_();<BR>DQ=1;<BR>for(j=10;j>0;j--);<BR>if(DQ==1)<BR>{<BR>temp=temp
| 0x80;<BR>}<BR>else<BR>{<BR>temp=temp |
0x00;<BR>}<BR>for(j=200;j>0;j--);<BR>}<BR>return(temp);<BR>}<BR> <BR>void
main(void)<BR>{<BR>TMOD=0x01;<BR>TH0=(65536-4000)/256;<BR>TL0=(65536-4000)%256;<BR>ET0=1;<BR>EA=1;<BR> <BR>while(resetpulse());<BR>writecommandtods18b20(0xcc);<BR>writecommandtods18b20(0x44);<BR>TR0=1;<BR>while(1)<BR>{<BR>;<BR>}<BR>}<BR> <BR>void
t0(void) interrupt 1 using 0<BR>{<BR>unsigned char
x;<BR>unsigned int
result;<BR> <BR>TH0=(65536-4000)/256;<BR>TL0=(65536-4000)%256;<BR>if(displaycount==2)<BR>{<BR>P0=displaycode[displaybuf[displaycount]]
|
0x80;<BR>}<BR>else<BR>{<BR>P0=displaycode[displaybuf[displaycount]];<BR>}<BR>P2=displaybit[displaycount];<BR>displaycount++;<BR>if(displaycount==8)<BR>{<BR>displaycount=0;<BR>}<BR> <BR>timecount++;<BR>if(timecount==150)<BR>{<BR>timecount=0;<BR>while(resetpulse());<BR>writecommandtods18b20(0xcc);<BR>writecommandtods18b20(0xbe);<BR>readdata[0]=readdatafromds18b20();<BR>readdata[1]=readdatafromds18b20();<BR>for(x=0;x<8;x++)<BR>{<BR>displaybuf[x]=16;<BR>}<BR>sflag=0;<BR>if((readdata[1]
&
0xf8)!=0x00)<BR>{<BR>sflag=1;<BR>readdata[1]=~readdata[1];<BR>readdata[0]=~readdata[0];<BR>result=readdata[0]+1;<BR>readdata[0]=result;<BR>if(result>255)<BR>{<BR>readdata[1]++;<BR>}<BR>}<BR>readdata[1]=readdata[1]<<4;<BR>readdata[1]=readdata[1]
& 0x70;<BR>x=readdata[0];<BR>x=x>>4;<BR>x=x &
0x0f;<BR>readdata[1]=readdata[1] |
x;<BR>x=2;<BR>result=readdata[1];<BR>while(result/10)<BR>{<BR>displaybuf[x]=result%10;<BR>result=result/10;<BR>x++;<BR>}<BR>displaybuf[x]=result;<BR>if(sflag==1)<BR>{<BR>displaybuf[x+1]=17;<BR>}<BR>x=readdata[0]
&
0x0f;<BR>x=x<<1;<BR>displaybuf[0]=(dotcode[x])%10;<BR>displaybuf[1]=(dotcode[x])/10;<BR>while(resetpulse());<BR>writecommandtods18b20(0xcc);<BR>writecommandtods18b20(0x44);<BR>}<BR>}
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