📄 上海齐济电子-应用技巧-pic16系列单片机与pc机串行通信的软硬件实现.htm
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<P align=justify><SPAN style="FONT-SIZE: 9pt">
cDCBConfig.parity = None</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> cDCBConfig.data
= 8</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> cDCBConfig.stop
= 1</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> lResult =
BuildCommDCB（cDCBConfig，DCB_COMM）
’按用户设定配置一个DCB结构</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> If lResult = 0
Then</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
OpenThePort = False</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> MsgBox
“无法建立DCB设备控制块”</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> Exit
Function</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> End
If</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> lResult =
SetCommState（lHandle，DCB_Comm）
’实际设置一个串口的DCB
</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> If lResult = 0
Then</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
OpenThePort = False</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> MsgBox
“无法建立DCB设备控制块”</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> Exit
Function</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> End
If</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> OpenThePort =
True</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt">End Function</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt">Private Sub SendHand ( )
’发送握手信号的子过程</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> Dim Nchars As
Long</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> Static Readbuff
As String * 1</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> Static
Writebuff As String * 1</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> Dim lpDCB As
DCB</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> Dim lRet As
Long</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> Dim lHandle As
Long</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> Dim
lpOverlapped As OVERLAPPED</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> Dim RNum As
Integer</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> MsgBox
“请把读卡器插在串口2上！”，</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
48，“提示窗口”</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> lHandle =
OpenThePort（COMM1,2400,None,8,1）</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> lRet =
PurgeComm( lHandle，1 ) ’清输出缓冲区</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> lRet =
PurgeComm( lHandle，0 ) ’清输入缓冲区</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> lRet =
GetCommState ( lHandle，lpDCB ) ’获得通讯口的状态</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt">Shand：</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> Writebuff＄=
Chr＄(&H8F)</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> lRet =
WriteFile (lHandle,Writebuff＄,1,Nchars,lpOverlapped ) </SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
’送握手信号入串口缓冲区</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> If lRet <= 0
Then</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
MsgBox “发送操作出错，卡握手信号未发送成功”， 16</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
GoTo Shand ’不成功则重发</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> Else</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
GoTo Qtest</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> End If</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> GoTo
Shand</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt">Qtest：</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> Readbuff$ =“ ”
’清除缓冲区为空</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt">Do While lHandle
’循环查询串口</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> RNum = 0
’设置读串口次数的指针为0</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt">ReadAgain：</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> lRet =
ReadFile( lHandle， Readbuff＄，1，Nchars，lpOverlapped
)</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> If lRet < 0
Then</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> MsgBox “读取应答信号时出错”，
16</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> End If</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> If lRet = 0
Then</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> If
RNum > 1000 Then ’只读1000次串口，以免陷入死循环</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
MsgBox </SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
"卡没有插接好或卡没有接在串口上!"</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
GoTo CloseP</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> End
If</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> RNum =
RNum + 1</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> GoTo
ReadAgain</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> End
If</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> If
Hex＄(Asc(Readbuff)) <> Hex＄(&HFF) Then GoTo Shand </SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
’回送码不正确则返回继续发送握手信号</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> Else</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> Label1.Caption =
“握手信号是：”</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
＋Hex＄(Asc(Readbuff＄))</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> Msgbox
“握手信号正确，已正确联机”</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt"> GoTo
CloseP</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt"> End
If</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt">Loop</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt">CloseP：lRet = CloseHandle(
lHandle )</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
If lRet = 0 Then</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
MsgBox “串行通讯口关闭成功”，</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
48，“提示窗口”</SPAN></P>
<P align=justify><SPAN
style="FONT-SIZE: 9pt">
End If</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt">End Sub</SPAN></P>
<P align=justify><SPAN style="FONT-SIZE: 9pt">
这里要注意的是：当PC机与单片机系统通信时，单片机数据存储区( RAM
)内的数据是十六进制，在信号线上传输的是十六进制数的ASCII码的二进制形式；而Windows系统下使用的是ANSI码，ANSI码仅在前126个与ASCII码相同。即在Win95下接收到的是十六进制数的ASCII码的字符串，可先转换为ANSI码后再在Win95下还原为十六进制数。<BR>
具体为：Code$=Hex＄(Asc ( Readbuff$ ) )<BR>
另外，由于32位API函数参数的数据类型的变化，所有整形参数都被换为长整型（Long）以支持32位的处理，这一点在设置返回值时尤其如此。</SPAN></P><B>
<P align=justify><SPAN style="FONT-SIZE: 9pt"><FONT color=#800080>6
结束语</FONT></SPAN></P></B>
<P align=justify><SPAN style="FONT-SIZE: 9pt">
以上的软硬件在我们的实践中达到了较为理想的效果。通过软件节省了硬件的开销，并通过在PIC16F84单片机系统和PC机双方的通信软件内增加握手信号，达到了软件数据校验的目的，获得了较高的通信可靠性。</SPAN></P><B>
<P align=center><SPAN style="FONT-SIZE: 9pt"><FONT color=#800080>参 考 文
献</FONT></SPAN></P></B>
<P align=justify><SPAN style="FONT-SIZE: 9pt">1 MICROCHIP CO. PIC16/17
MICROCO-NTROLLER DATA BOOK. 1995/1996 <BR>2 李东星等.
PIC16CXX系列单片机应用设计. 高奇电子科技公司，1996.10 <BR>3 美 Darwin Boyle等. Visual Basic 4
Developer’s Guide. 北京：机械工<BR> 业出版社，1997.
</SPAN><!-- InstanceEndEditable --></P></TD></TR>
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