vb_mscomm

我曾经在工程中使用的部分源代码

发送子程序：
   length = strHexToByteArray("1b70", bytSendByte())
   If length > 0 Then
       MSComm1.Output = bytSendByte
   End If


接收子程序：
Private Sub MSComm1_OnComm()
Select Case MSComm1.CommEvent
'错误事件
    Case comEventBreak
    Case comEventCDTO  'CD (RLSD) 超时
    Case comEventCTSTO  'CTS 超时
    Case comEvReceive
    lbl(0).Caption = lbl(0).Caption & MSComm1.Input
End Select
End Sub

必须调用的子函数：
Function strHexToByteArray(strText As String, bytByte() As Byte) As Integer
    Dim HexData As Integer          '十六进制(二进制)数据字节对应值
    Dim hstr As String * 1          '高位字符
    Dim lstr As String * 1          '低位字符
    Dim HighHexData As Integer      '高位数值
    Dim LowHexData As Integer       '低位数值
    Dim HexDataLen As Integer       '字节数
    Dim StringLen As Integer        '字符串长度
    Dim Account As Integer          '计数
    strTestn = ""                   '设初值
    HexDataLen = 0
    strHexToByteArray = 0
    StringLen = Len(strText)
    Account = StringLen \ 2
    ReDim bytByte(Account)
    For n = 1 To StringLen
        Do                                              '清除空格
            hstr = Mid(strText, n, 1)
            n = n + 1
            If (n - 1) > StringLen Then
                HexDataLen = HexDataLen - 1
                Exit For
            End If
        Loop While hstr = " "
        
        Do
            lstr = Mid(strText, n, 1)
            n = n + 1
            If (n - 1) > StringLen Then
                HexDataLen = HexDataLen - 1
                
                Exit For
            End If
        Loop While lstr = " "
        n = n - 1
        If n > StringLen Then
            HexDataLen = HexDataLen - 1
            Exit For
        End If
        
        HighHexData = ConvertHexChr(hstr)
        LowHexData = ConvertHexChr(lstr)
        
        If HighHexData = -1 Or LowHexData = -1 Then     '遇到非法字符中断转化
            HexDataLen = HexDataLen - 1
            
            Exit For
        Else
            
            HexData = HighHexData * 16 + LowHexData
            bytByte(HexDataLen) = HexData
            HexDataLen = HexDataLen + 1
        End If
                        
    Next n
    
    If HexDataLen > 0 Then                              '修正最后一次循环改变的数值
        HexDataLen = HexDataLen - 1
        ReDim Preserve bytByte(HexDataLen)
    Else
        ReDim Preserve bytByte(0)
    End If
    
    
    If StringLen = 0 Then                               '如果是空串,则不会进入循环体
        strHexToByteArray = 0
    Else
        strHexToByteArray = HexDataLen + 1
    End If
End Function

Function ConvertHexChr(str As String) As Integer
    Dim test As Integer
    test = Asc(str)
    If test >= Asc("0") And test <= Asc("9") Then
        test = test - Asc("0")
    ElseIf test >= Asc("a") And test <= Asc("f") Then
        test = test - Asc("a") + 10
    ElseIf test >= Asc("A") And test <= Asc("F") Then
        test = test - Asc("A") + 10
    Else
        test = -1                                       '出错信息
    End If
    ConvertHexChr = test
End Function