用VB实现基于USB的虚拟串口通讯

在VB中利用API进行串口通信一般来说，在VB中编写串口通讯程序，首先考虑到是使用MSComm控件，可是该控件不能设置超时，而且对许多内部的参数进行了隐藏，从而不能满足有些具体的工作。

而使用API进行串口通信，大多是使用VC，很少见到完整的VB代码，为此，我编写了这个模块。

同时，由于串口通信是基于字节流的，为方便程序设计，还编写了三个简单的辅助函数，并写了一个详细的测试代码。

Option ExplicitOption Base 0Private Declare Function CreateFile Lib "kernel32" Alias "CreateFileA" (ByVal lpFileName As String, ByVal dwDesiredAccess As Long, ByVal dwShareMode As Long, ByVal lpSecurityAttributes As Long, ByVal dwCreationDisposition As Long, ByVal dwFlagsAndAttributes As Long, ByVal hTemplateFile As Long) As LongPrivate Declare Function ReadFile Lib "kernel32" (ByVal hFile As Long, lpBuffer As Any, ByVal nNumberOfBytesToRead As Long, lpNumberOfBytesRead As Long, ByVal lpOverlapped As Long) As LongPrivate Declare Function WriteFile Lib "kernel32" (ByVal hFile As Long, lpBuffer As Any, ByVal nNumberOfBytesToWrite As Long, lpNumberOfBytesWritten As Long, ByVal lpOverlapped As Long) As LongPrivate Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long Private Const GENERIC_READ = &H80000000Private Const GENERIC_WRITE = &H40000000Private Const OPEN_EXISTING = 3Private Const INVALID_HANDLE_VALUE = -1Private Declare Function GetCommState Lib "kernel32" (ByVal nCid As Long, lpDCB As DCB) As LongPrivate Declare Function SetCommState Lib "kernel32" (ByVal hCommDev As Long, lpDCB As DCB) As LongPrivate Declare Function SetCommTimeouts Lib "kernel32" (ByVal hFile As Long, lpCommTimeouts As COMMTIMEOUTS) As LongPrivate Declare Function SetupComm Lib "kernel32" (ByVal hFile As Long, ByVal dwInQueue As Long, ByVal dwOutQueue As Long) As LongPrivate Declare Function PurgeComm Lib "kernel32" (ByVal hFile As Long, ByVal dwFlags As Long) As LongPrivate Const PURGE_TXABORT = &H1 ' Kill the pending/current writes to the comm port.Private Const PURGE_RXABORT = &H2 ' Kill the pending/current reads to the comm port.Private Const PURGE_TXCLEAR = &H4 ' Kill the transmit queue if there. Private Const PURGE_RXCLEAR = &H8 ' Kill the typeahead buffer if there. Private Type DCBDCBlength As LongBaudRate As LongfBitFields As Long 'See Comments in Win32API.TxtwReserved As IntegerXonLim As IntegerXoffLim As IntegerByteSize As ByteParity As ByteStopBits As ByteXonChar As ByteXoffChar As ByteErrorChar As ByteEOFChar As ByteEvtChar As BytewReserved1 As Integer 'Reserved; Do Not UseEnd TypePrivate Type COMMTIMEOUTSReadIntervalTimeout As LongReadTotalTimeoutMultiplier As LongReadTotalTimeoutConstant As LongWriteTotalTimeoutMultiplier As LongWriteTotalTimeoutConstant As LongEnd TypePrivate Declare Function SafeArrayGetDim Lib "oleaut32.dll" (ByRef saArray() As Any) As Long'串口操作演示Sub Main()Dim hComm As LongDim szTest As String'打开串口1hComm = OpenComm(1)If hComm <> 0 Then'设置串口通讯参数SetCommParam hComm'设置串口超时SetCommTimeOut hComm, 2, 3'向串口写入字符串123szTest = "123"WriteComm hComm, StringToBytes(szTest)'读串口szTest = BytesToString(ReadComm(hComm))Debug.Print szTest'关闭串口CloseComm hCommEnd IfEnd Sub'打开串口Function OpenComm(ByVal lComPort As Long) As LongDim hComm As LonghComm = CreateFile("COM" & lComPort, GENERIC_READ Or GENERIC_WRITE, 0, 0, OPEN_EXISTING, 0, 0)If hComm = INVALID_HANDLE_VALUE ThenOpenComm = 0ElseOpenComm = hCommEnd IfEnd Function'关闭串口Sub CloseComm(hComm As Long)CloseHandle hCommhComm = 0End Sub'读串口Function ReadComm(ByVal hComm As Long) As Byte()Dim dwBytesRead As LongDim BytesBuffer() As ByteReDim BytesBuffer(4095)ReadFile hComm, BytesBuffer(0), UBound(BytesBuffer) + 1, dwBytesRead, 0 If dwBytesRead > 0 ThenReDim Preserve BytesBuffer(dwBytesRead)ReadComm = BytesBufferEnd IfEnd Function'写串口Function WriteComm(ByVal hComm As Long, BytesBuffer() As Byte) As LongDim dwBytesWriteIf SafeArrayGetDim(BytesBuffer) = 0 Then Exit FunctionWriteFile hComm, BytesBuffer(0), UBound(BytesBuffer) + 1, dwBytesWrite, 0 WriteComm = dwBytesWriteEnd Function'设置串口通讯参数Function SetCommParam(ByVal hComm As Long, Optional ByVal lBaudRate As Long = 9600, _Optional ByVal cByteSize As Byte = 8, Optional ByVal cStopBits As Byte = 0, _Optional ByVal cParity As Byte = 0, Optional ByVal cEOFChar As Long = 26) As BooleanDim dc As DCBIf hComm = 0 Then Exit FunctionIf GetCommState(hComm, dc) Thendc.BaudRate = lBaudRatedc.ByteSize = cByteSizedc.StopBits = cStopBitsdc.Parity = cParitydc.EOFChar = cEOFCharSetCommParam = CBool(SetCommState(hComm, dc))End IfEnd Function'设置串口超时Function SetCommTimeOut(ByVal hComm As Long, Optional ByVal dwReadTimeOut As Long = 2, _Optional ByVal dwWriteTimeOut As Long = 3) As BooleanDim ct As COMMTIMEOUTSIf hComm = 0 Then Exit Functionct.ReadIntervalTimeout = dwReadTimeOut '读操作时，字符间超时ct.ReadTotalTimeoutMultiplier = dwReadTimeOut '读操作时，每字节超时ct.ReadTotalTimeoutConstant = dwReadTimeOut '读操作时，固定超时（总超时=每字节超时*字节数+固定超时）ct.WriteTotalTimeoutMultiplier = dwWriteTimeOut '写操作时，每字节超时ct.WriteTotalTimeoutConstant = dwWriteTimeOut '写操作时，固定超时（总超时=每字节超时*字节数+固定超时）SetCommTimeOut = CBool(SetCommTimeouts(hComm, ct))End Function'设置串口读写缓冲区大小Function SetCommBuffer(ByVal hComm As Long, Optional ByVal dwBytesRead As Long = 1024, _Optional ByVal dwBytesWrite As Long = 512) As BooleanIf hComm = 0 Then Exit FunctionSetCommBuffer = CBool(SetupComm(hComm, dwBytesRead, dwBytesWrite))End Function'清空串口缓冲区Sub ClearComm(ByVal hComm As Long, Optional ByVal InBuffer As Boolean = True, Optional ByVal OutBuffer As Boolean = True)If hComm = 0 Then Exit SubIf InBuffer And OutBuffer Then '清空输入输出缓冲区PurgeComm hComm, PURGE_TXABORT Or PURGE_RXABORT Or PURGE_TXCLEAR Or PURGE_RXCLEARElseIf InBuffer Then '清空输入缓冲区PurgeComm hComm, PURGE_RXABORT Or PURGE_RXCLEARElseIf OutBuffer Then '清空输出缓冲区PurgeComm hComm, PURGE_TXABORT Or PURGE_TXCLEAREnd IfEnd Sub'辅助函数：BSTR字符串转换为CHAR字符串Function StringToBytes(ByVal szText As String) As Byte()If Len(szText) > 0 ThenStringToBytes = StrConv(szText, vbFromUnicode)End IfEnd Function'辅助函数：CHAR字符串转换为BSTR字符串Function BytesToString(bytesText() As Byte) As StringIf SafeArrayGetDim(bytesText) <> 0 ThenBytesToString = StrConv(bytesText, vbUnicode)End IfEnd Function'辅助函数：获得CHAR字符串长度Function Byteslen(bytesText() As Byte) As LongIf SafeArrayGetDim(bytesText) <> 0 Then Byteslen = UBound(bytesText) + 1 End IfEnd Function。

2009年2月第2期电子测试ELECTRONIC T ESTJan.2009No.2电子测试E LECTRO NIC TE ST基于VB的串口通信在虚拟现实系统中的应用高杰,张玉(合肥电子工程学院合肥230037)摘要:在W indo wsXP的软件环境下,以3D引擎技术为基础,创建3D虚拟空间,利用影像处理系统获取现实场景中的影像并与虚拟场景合成,实现最佳的图像融合效果;利用V B中的M SCo mm控件实现工业控制计算机与动力系统、影像处理系统、灯光照明系统的串口通信,将现实世界中的速度信息通过采集处理程序传递给虚拟场景,控制场景的视角变化和位移变化,较好地保证了任意时间作用于虚拟空间的信号与现实中变送器发出的信号的同步性,最终达到对3D虚拟空间的综合控制。

关键词:串口通信;虚拟空间;速度;方向中图分类号:T P274文献标识码:AApplication of serial port comm unicatio n in thevirtual reality system based on VBGao Jie,Zhang Yu(EEI,Hefei230037)Abstract:Based on technolo gy of3D engine,the paper establishes3D virtual space,acquire actu-al image w ith imag e m anipulation system and com pose it w ith virtual screen in the softw are cir-cum stance of w indow sXP;realizes the Serial Port Comm unicatio n in com puter,motivity system, im age m anipulatio n sy stem and lig hting system by MSCom m control of VB.T ransfer actual speed to virtual screen w ith collectio n and disposing process to contr ol visual ang le and displace-m ent,guarantee iso chronous betw een virtual sig nal and actual signal and finally achieves sy n-thetical co ntro l to3D virtual space.Keywords:Serial Po rt Comm unication;virtual space;speed;dir ectio n0引言虚拟现实(Virtua-l Reality,简称VR)作为一门新兴的技术,其应用已从游戏机和主题游乐园扩展到工业、商业、医学和军事等多个领域。

用VB写的modbusrtu模式通讯源码‘用VB 写的modbus rtu模式通讯源码，已在台达PLC上调试通过Private Sub CmdOpen_Click()On Error Resume NextIf (MSComm1.PortOpen) Then ‘打开/关闭串口MSComm1.PortOpen = FalseElseMSComm1.PortOpen = TrueEnd IfIf (MSComm1.PortOpen) ThenCmdOpen.Caption = "关闭串口"Shape5.FillStyle = vbFSSolidElseCmdOpen.Caption = "打开串口"Shape5.FillStyle = vbFSTransparentEnd IfIf Err ThenMsgBox Error$, 48, "错误码信息"Exit SubEnd IfEnd SubPrivate Sub Combo1_Click()/doc/df18763589.html,mPort = Combo1.ListIndex + 1End SubPrivate Sub Combo2_Click()Call SettingEnd SubPrivate Sub Combo3_Click()Call SettingEnd SubPrivate Sub Combo4_Click()Call SettingEnd SubPrivate Sub Combo5_Click()Call SettingEnd SubPrivate Sub Command1_Click()‘S hape1.FillStyle = vbFSSolidDim Y0_status As ByteDim Sendstr As StringDim i As Integer, j As IntegerSendstr = "01 01 05 00 00 10 "HexSend (Sendstr)Sleep (30)HexSend (Sendstr)End SubPrivate Function HexSend(Sendstr As String) As Integer Dim outbuf() As ByteDim Temp(0) As ByteDim crc As String, Sendstrls As StringDim sendlen As IntegerDim i As Integer, j As IntegerIf Sendstr = "" ThenMsgBox "发送数据不能为空！"HexSend = 0Exit FunctionEnd IfS endstrls = Trim(Sendstr) ‘去掉空格sendlen = Len(Sendstrls) + 1 ‘取长度j = 0ReDim outbuf(1 To sendlen \ 3) As ByteFor i = 1 To sendlen Step 3j = j + 1outbuf(j) = Val("&H" & CStr(Mid(Sendstrls, i, 2)))Next icrc = Crc16(outbuf)ReDim Preserve outbuf(1 T o (sendlen \ 3 + 2)) As Byte ‘加上CRC校验码outbuf(sendlen \ 3 + 1) = Val("&H" & CStr(Mid(crc, 1, 2)))outbuf(sendlen \ 3 + 2) = Val("&H" & CStr(Mid(crc, 3, 2)))For i = 1 To (sendlen \ 3 + 2)Temp(0) = outbuf(i)MSComm1.Output = TempNext iFor i = 1 To 2000Next iHexSend = 1End FunctionPrivate Function Setting()MSComm1.Settings = CStr(Combo2.Text) & "," & CStr(Combo3.Text) & "," & CStr(Combo4.Text) & "," & CStr(Combo5.Text) End FunctionPrivate Sub Command2_Click()‘If (MSComm1.RThreshold = 0) Then‘MSComm1.RTh reshold = 1‘Else‘MSComm1.RThreshold = 0‘End IfLabel11.Caption = "接收个数:" & CStr(ReceCount) & " " & "接收帧数：" & CStr(Framecount) End SubPrivate Sub Form_Load()Combo1.AddItem ("COM1")Combo1.AddItem ("COM2")Combo1.AddItem ("COM3")Combo1.AddItem ("COM4")Combo1.AddItem ("COM5")Combo1.ListIndex = 0Combo2.AddItem ("2400")Combo2.AddItem ("4800")Combo2.AddItem ("9600")Combo2.AddItem ("11520")Combo2.ListIndex = 0Combo3.AddItem ("E")Combo3.AddItem ("O")Combo3.AddItem ("N")Combo3.ListIndex = 2Combo4.AddItem ("6")Combo4.AddItem ("7")Combo4.AddItem ("8")Combo4.ListIndex = 2Combo5.AddItem ("1")Combo5.AddItem ("2")Combo5.ListIndex = 0ReceCount = 0End SubPrivate Function Crc16(data() As Byte) As StringDim CRC16Lo As Byte, CRC16Hi As Byte ‘CRC寄存器Dim CL As Byte, CH As Byte ‘多项式码&HA001Dim CrcLo As String, CrcHi As StringDim SaveHi As Byte, SaveLo As ByteDim i As IntegerDim Flag As IntegerCRC16Lo = &HFFCRC16Hi = &HFFCL = &H1CH = &HA0For i = 1 To UBound(data)CRC16Lo = CRC16Lo Xor data(i) ‘每一个数据与CRC寄存器进行异或For Flag = 0 To 7SaveHi = CRC16HiSaveLo = CRC16LoCRC16Hi = CRC16Hi \ 2 ‘高位右移一位CRC16Lo = CRC16Lo \ 2 ‘低位右移一位If ((SaveHi And &H1) = &H1) Then ‘如果高位字节最后一位为1CRC16Lo = CRC16Lo Or &H80 ‘则低位字节右移后前面补1 End If ‘否则自动补0If ((SaveLo And &H1) = &H1) Then ‘如果LSB为1，则与多项式码进行异或CRC16Hi = CRC16Hi Xor CHCRC16Lo = CRC16Lo Xor CLEnd IfNext FlagNext iIf Len(Hex(CRC16Hi)) = 1 ThenCrcHi = "0" + Hex(CRC16Hi)ElseCrcHi = Hex(CRC16Hi)End IfIf Len(Hex(CRC16Lo)) = 1 ThenCrcLo = "0" + Hex(CRC16Lo)ElseCrcLo = Hex(CRC16Lo)End IfCrc16 = CrcLo & CrcHiEnd FunctionPrivate Sub MSComm1_OnComm()Dim inpu() As ByteDim i As IntegerDim tempstr As String, Strdata As StringSelect Case /doc/df18763589.html,mEvent Case comEvReceive ‘接收事件tempstr = MSComm1.Inputinpu() = tempstrFramecount = Framecount + 1 ‘帧个数加1If (Framecount = 1) Thenframepoint(Framecount) = UBound(inpu) + 1 ‘第一帧帧尾Elseframepoint(Framecount) = framepoint(Framecount - 1) + UBound(inpu) + 1 ‘第二帧开始指针End IfFor i = 0 To UB ound(inpu) ‘将字符转换为数组If (Len(Hex(inpu(i))) = 1) ThenStrdata = Strdata & "0" & Hex(inpu(i)) & " "ElseStrdata = Strdata & Hex(inpu(i)) & " "End IfNext iFor i = ReceCount + 1 To UBound(inpu) + 1 ‘数据进入缓冲区Recebuf(i) = inpu(i - 1)NextReceCount = ReceCount + UBound(inpu) + 1TextReceive.Text = TextReceive.Text & StrdataStrdata = ""Case comEvSendEnd SelectEnd SubPrivate Function RtuCheck(data() As Byte) As IntegerDim CrcHi As Byte, CrcLo As ByteDim Checkdata() As ByteDim i As IntegerDim crc As StringCrcHi = data(UBound(data))CrcLo = data(UBound(data) - 1)ReDim Checkdata(1 To (UBound(data) - 1)) As ByteFor i = 1 To (UBound(data) - 1) ‘附值Checkdata(i) = data(i - 1)Nextcrc = Crc16(Checkdata)If (CrcLo = Val("&H" & CStr(Mid(crc, 1, 2))) And CrcHi = Val("&H" & CStr(Mid(crc, 3, 2)))) Then RtuCheck = 1ElseRtuCheck = 0End IfEnd Function。

串口通讯及其在VB平台下的实现摘要：本文首先介绍串行通讯的基础知识，然后结合示例剖析在VB平台下的串口通讯的编程技巧。

随着计算机系统的普及与外围设备技术的发展，计算机与外围设备之间的通讯就显得越来越重要了。

由于串行通信是在一根传输线上一位一位的传送信息，所用的传输线少，并且可以借助现成的电话网进行信息传送，因此，特别适合于远距离传输。

对于那些与计算机相距不远的人－机交换设备和串行存储的外部设备如终端、打印机、逻辑分析仪、磁盘等，采用串行方式交换数据也很普遍。

在实时控制和管理方面，采用多台微机处理机组成分级分布控制系统中，各CPU之间的通信一般都是串行方式。

所以串行接口是微机应用系统常用的接口，而相应的应用程序也成为今年来研究的热点。

本文旨在阐述一般的穿口通讯的原理及其程序设计，希望借此能够抛砖引玉，为更深入的研究打下一定的基础。

一、串行通讯的基本原理所谓"串行通信"是指外设和计算机间使用一根数据信号线,数据在一根数据信号线上按位进行传输，每一位数据都占据一个固定的时间长度。

这种通信方式使用的数据线少，在远距离通信中可以节约通信成本，当然，其传输速度比并行传输慢。

相比之下，由于高速率的要求，处于计算机内部的CPU与串口之间的通讯仍然采用并行的通讯方式，所以串行口的本质就是实现CPU与外围数据设备的数据格式转换（或者称为串并转换器），即当数据从外围设备输入计算机时，数据格式由位(bit)转化为字节数据；反之，当计算机发送下行数据到外围设备时，串口又将字节数据转化为位数据。

二、串口通讯的程序设计原理前面介绍了串行通讯的基本原理，那么如何在程序设计中实现它呢？事实上，这个过程并不复杂，一般有两种实现途径：其一就是使用MSCOMM控件，此控件提供很多方便操作的属性和方法，利用它们可以很方便地实现你的目的；另外一种途径就是使用Windows API，微软为开发者提供了很多相关的串行操作的编程接口，使用这些接口，可以很完成更为强大的功能。

VB串口编程实例介绍VB（Visual Basic）是一种基于对象的编程语言，可用于开发Windows应用程序。

串口编程是指通过串行通信接口与外部设备进行数据交互。

本文将介绍如何使用VB进行串口编程，以实现与外部设备的通信。

前提条件在开始编写VB串口程序之前，需要确保以下条件已满足： - 安装了Visual Studio开发环境，可以选择最新版本的Visual Studio Community免费版。

- 确保计算机上有可用的串口（如COM1、COM2等）或USB转串口适配器。

步骤1. 创建新项目打开Visual Studio，选择创建一个新的VB Windows应用程序项目。

2. 添加控件在窗体上添加以下控件： - 一个ListBox控件用于显示接收到的数据。

- 两个Button控件分别用于打开和关闭串口。

- 一个ComboBox控件用于选择串口号。

- 一个TextBox控件用于输入要发送的数据。

- 一个Button控件用于发送数据。

3. 设置串口属性在窗体代码中添加如下代码：Imports System.IO.PortsPublic Class Form1Dim serialPort As New SerialPort()Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Lo ad' 获取可用的串口号并添加到ComboBox中Dim ports As String() = SerialPort.GetPortNames()ComboBox1.Items.AddRange(ports)End SubPrivate Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click' 打开串口TryserialPort.PortName = ComboBox1.SelectedItem.ToString()serialPort.BaudRate = 9600serialPort.Parity = Parity.NoneserialPort.DataBits = 8serialPort.StopBits = StopBits.OneserialPort.Open()Button1.Enabled = FalseButton2.Enabled = TrueCatch ex As ExceptionMessageBox.Show("无法打开串口：" + ex.Message)End TryEnd SubPrivate Sub Button2_Click(sender As Object, e As EventArgs) Handles Button 2.Click' 关闭串口TryserialPort.Close()Button1.Enabled = TrueButton2.Enabled = FalseCatch ex As ExceptionMessageBox.Show("无法关闭串口：" + ex.Message)End TryEnd SubEnd Class4. 接收数据和发送数据在窗体代码中添加如下代码：Imports System.IO.PortsPublic Class Form1Dim serialPort As New SerialPort()Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Lo ad' 获取可用的串口号并添加到ComboBox中Dim ports As String() = SerialPort.GetPortNames()ComboBox1.Items.AddRange(ports)End SubPrivate Sub Button1_Click(sender As Object, e As EventArgs) Handles Button 1.Click' 打开串口' 省略部分代码...AddHandler serialPort.DataReceived, AddressOf DataReceivedHandlerserialPort.Open()Button1.Enabled = FalseButton2.Enabled = TrueEnd SubPrivate Sub Button2_Click(sender As Object, e As EventArgs) Handles Button 2.Click' 关闭串口' 省略部分代码...RemoveHandler serialPort.DataReceived, AddressOf DataReceivedHandler serialPort.Close()Button1.Enabled = TrueButton2.Enabled = FalseEnd SubPrivate Sub DataReceivedHandler(sender As Object, e As SerialDataReceivedE ventArgs)' 接收数据并显示在ListBox中Dim data As String = serialPort.ReadLine()ListBox1.Invoke(Sub() ListBox1.Items.Add(data))End SubPrivate Sub Button3_Click(sender As Object, e As EventArgs) Handles Button 3.Click' 发送数据If serialPort.IsOpen ThenDim dataToSend As String = TextBox1.TextserialPort.WriteLine(dataToSend)TextBox1.Clear()ElseMessageBox.Show("请先打开串口")End IfEnd SubEnd Class5. 运行程序点击运行按钮，程序将打开一个窗口，其中包含串口选择、打开/关闭串口、接收数据和发送数据的功能。

VB6.0环境下基于USB的虚拟串口通讯实现摘要：以ftdi公司的ft232bl芯片为核心设计并实现了基于usb 接口的计算机与单片机之间的虚拟串口通讯。

单片机采用philips 公司p89系列单片机，完成数据的存储。

计算机在windows环境下利用mscomm通讯控件实现上位机与下位机之间的数据传输。

在此提出了pc机对虚拟串口的自动识别方法，并提供了程序的源代码。

实验结果表明，用虚拟串口实现计算机与单片机之间的usb通信，具有速度快，软件实现简单等优点。

关键词：vb6.0； usb口； ft232bl；虚拟串口引言数据传输是现代通讯过程中的一个重要环节，在数据传输过程中，不仅要求数据传输的准确率要高，而且要求速度快、连接方便。

传统的rs 232串口通讯和并口通讯都存在传输速度低、扩展性差、安装麻烦等缺点，而基于usb接口的数据传输系统能够较好地解决这些问题。

目前，usb接口以其传输速率高、即插即用、支持热插拔等优点，逐步成为pc机的标准接口。

本文中的数据传输系统采用了usb接口进行上位机与下位机之间的数据通讯。

下位机采用philips 公司p89系列单片机，完成数据的存储。

上位机通过vb6.0编程，实现上位机与下位机之间的数据传输。

1数据传输系统的总体设计系统的硬件部分主要包括2部分：上位机端和下位机端。

上位机采用pc机或笔记本电脑，操作系统为windows xp，实现上位机和下位机之间的数据传输、显示、处理、存储及查询功能。

系统的下位机采用philips公司p89系列单片机，完成数据的存储。

下位机为一个手持的数据存储仪，由usb转串口数据转换模块、ttl转rs 422总线模块、中央处理模块、显示模块、存储模块、电源模块等组成。

上位机与下位机的连接利用pc机自带的usb接口，原理框图如图1所示。

图1数据传输系统原理框图把数据记录卡插入数据存储仪内，可把卡内数据转存到存储模块。

数据存储仪通过usb口与pc机连接，把所存数据传输到上位机，上位机对数据进行显示、处理及存储。

VB中串口通讯的实现VB中串口通讯的实现一、概述串口通讯作为一种古老而又灵活的通讯方式，被广泛地应用于PC间的通讯以及PC和单片机之间的通讯之中。

提到串口通讯的编程，人们往往立刻想到C、汇编等对系统底层操作支持较好的编程语言以及大串繁琐的代码。

实际上，只要我们借助相关ActiveX控件的帮助，即使是在底层操作一向不被人看好的VB 中，一样能够实现串口通讯，甚至其实现方法和C、汇编相比，要更加快捷方便。

下面，笔者就介绍一下在VB中实现串口通讯的方法。

在Visual Basic中有一个名为Microsoft Communication Control（简称MSComm）的通讯控件。

我们只要通过对此控件的属性和事件进行相应编程操作，就可以轻松地实现串口通讯。

下面，笔者就简要地介绍一下MSComm控件的使用方法。

二、MSComm控件的主要属性、事件1、MSComm的属性由于MSComm控件属性很多，在此笔者仅介绍与实现串口通讯密切相关的核心属性。

Commport：设置通讯所占用的串口号。

如设成1（默认值），表示对Com1进行操作。

Setting：对串口通讯的相关参数。

包括串口通讯的比特率，奇偶校验，数据位长度、停止位等。

其默认值是“9600,N,8,1”，表示串口比特率是9600bit/s，不作奇偶校验，8位数据位，1个停止位。

Portopen：设置串口状态，值为True时打开串口，值为False时关闭串口。

Input：从输入寄存器读取数据，返回值为从串口读取的数据内容，同时输入寄存器将被清空。

Ouput：发送数据到输出寄存器。

InBufferCount：设置输入寄存器所存储的字符数，当将其值设为0时，则输入寄存器将被清空。

InputMode：设置从输入寄存器中读取数据的形式。

若值为0，则表示以文本形式读取；值为1，则表示以二进制形式读取。

OutBufferCount：设置输出寄存器所存储的字符数，当将其值设为0时，则输出寄存器将被清空。