计米器

概述

介绍解析计米器数据

稳定解析

2025年11月28日，鼎盈（沪联）反应软件中获取计米器数据不稳定，一直跳，是因为之前的解析没有校验 CRC ，今日在解析时加入该功能后接受数据很稳定

下面是 MudBus RTU 通信时进行 CRC64 校验时使用的工具，只需要使用一个函数 GetCRC，传入要被计算的字符串，得到4个字符长度的 CRC 的校验码

Option Explicit

'VB6实现CRC的工具类
'字节值表的方法

Private Function GetCRCHi(Ind As Long) As Byte
    GetCRCHi = Choose(Ind + 1, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, _
    &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, _
    &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, _
    &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, _
    &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, _
    &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, _
    &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, _
    &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, _
    &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, _
    &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, _
    &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, _
    &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, _
    &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, _
    &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, _
    &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H0, &HC1, &H81, _
    &H40, &H1, &HC0, &H80, &H41, &H0, &HC1, &H81, &H40, &H1, &HC0, &H80, &H41, &H1, &HC0, &H80, _
    &H41, &H0, &HC1, &H81, &H40)
End Function

Private Function GetCRCLo(Ind As Long) As Byte
    GetCRCLo = Choose(Ind + 1, &H0, &HC0, &HC1, &H1, &HC3, &H3, &H2, &HC2, &HC6, &H6, &H7, &HC7, _
    &H5, &HC5, &HC4, &H4, &HCC, &HC, &HD, &HCD, &HF, &HCF, &HCE, &HE, &HA, &HCA, &HCB, &HB, &HC9, _
    &H9, &H8, &HC8, &HD8, &H18, &H19, &HD9, &H1B, &HDB, &HDA, &H1A, &H1E, &HDE, &HDF, &H1F, &HDD, _
    &H1D, &H1C, &HDC, &H14, &HD4, &HD5, &H15, &HD7, &H17, &H16, &HD6, &HD2, &H12, &H13, &HD3, &H11, _
    &HD1, &HD0, &H10, &HF0, &H30, &H31, &HF1, &H33, &HF3, &HF2, &H32, &H36, &HF6, &HF7, &H37, &HF5, _
    &H35, &H34, &HF4, &H3C, &HFC, &HFD, &H3D, &HFF, &H3F, &H3E, &HFE, &HFA, &H3A, &H3B, &HFB, &H39, _
    &HF9, &HF8, &H38, &H28, &HE8, &HE9, &H29, &HEB, &H2B, &H2A, &HEA, &HEE, &H2E, &H2F, &HEF, &H2D, _
    &HED, &HEC, &H2C, &HE4, &H24, &H25, &HE5, &H27, &HE7, &HE6, &H26, &H22, &HE2, &HE3, &H23, &HE1, _
    &H21, &H20, &HE0, &HA0, &H60, &H61, &HA1, &H63, &HA3, &HA2, &H62, &H66, &HA6, &HA7, &H67, &HA5, _
    &H65, &H64, &HA4, &H6C, &HAC, &HAD, &H6D, &HAF, &H6F, &H6E, &HAE, &HAA, &H6A, &H6B, &HAB, &H69, _
    &HA9, &HA8, &H68, &H78, &HB8, &HB9, &H79, &HBB, &H7B, &H7A, &HBA, &HBE, &H7E, &H7F, &HBF, &H7D, _
    &HBD, &HBC, &H7C, &HB4, &H74, &H75, &HB5, &H77, &HB7, &HB6, &H76, &H72, &HB2, &HB3, &H73, &HB1, _
    &H71, &H70, &HB0, &H50, &H90, &H91, &H51, &H93, &H53, &H52, &H92, &H96, &H56, &H57, &H97, &H55, _
    &H95, &H94, &H54, &H9C, &H5C, &H5D, &H9D, &H5F, &H9F, &H9E, &H5E, &H5A, &H9A, &H9B, &H5B, &H99, _
    &H59, &H58, &H98, &H88, &H48, &H49, &H89, &H4B, &H8B, &H8A, &H4A, &H4E, &H8E, &H8F, &H4F, &H8D, _
    &H4D, &H4C, &H8C, &H44, &H84, &H85, &H45, &H87, &H47, &H46, &H86, &H82, &H42, &H43, &H83, &H41, _
    &H81, &H80, &H40)
End Function

'将使用字符串表示的数值转换为字节数组
Public Function String2ByteArray(ByVal vData As String) As Byte()
    Dim byteInstruction() As Byte
    Dim i As Long
    If Len(vData) Mod 2 = 0 And Len(vData) <> 0 Then '检验16进制字符串长
        ReDim byteInstruction(Len(vData) / 2 - 1)
        For i = 0 To Len(vData) - 1 Step 2
           byteInstruction(i / 2) = Val("&H" & Mid(vData, i + 1, 2))
        Next
    End If

    String2ByteArray = byteInstruction
End Function


'传入字符串
'返回CRC的校验码
'返回值是用字符串表示的16进制
Public Function GetCRC(ByVal vData As String) As String
    Dim arrByteInstruction() As Byte
    arrByteInstruction = String2ByteArray(vData)

    Dim lCRC As Long
    lCRC = CRC16(arrByteInstruction)

    Dim szCRC As String
    szCRC = Hex(lCRC)

    GetCRC = szCRC
End Function

'传入：字节数组
'返回：CRC校验码的整数类型
'将返回的整数类型通过Hex(整数类型校验码)转换为16进制的字符串
Public Function CRC16(data() As Byte) As Long

    Dim CRC16Hi As Byte
    Dim CRC16Lo As Byte

    CRC16Hi = &HFF
    CRC16Lo = &HFF

    Dim i As Integer
    Dim iIndex As Long

    For i = 0 To UBound(data)

    iIndex = CRC16Hi Xor data(i)

    CRC16Hi = CRC16Lo Xor GetCRCHi(iIndex) '低位处理

    CRC16Lo = GetCRCLo(iIndex) '高位处理

    Next i

    Dim ReturnData(1) As Byte
    Dim test As Long

    ReturnData(0) = CRC16Hi 'CRC低位

    ReturnData(1) = CRC16Lo 'CRC高位

    test = Val(str(ReturnData(0))) * 256 + Val(str(ReturnData(1)))

    CRC16 = test

End Function

下面是对接收到的数据进行 CRC 校验，传入参数是下位机响应来的一个完整的数据（包含最后4位长度的 CRC），校验通过返回 True 相反则返回 false 表示数据非法，不要显示给用户使用

Public Function CheckCRC(ByVal str As String) As Boolean
    If Len(str) < 4 Then
        CheckCRC = False
        Exit Function
    End If
    
    Dim actualCRC As String
    actualCRC = Right$(str, 4)
    
    Dim leftStr As String
    leftStr = Left$(str, Len(str) - 4)
    
    Dim expectedCRC As String
    expectedCRC = crc.GetCRC(leftStr)

    If expectedCRC = actualCRC Then
        CheckCRC = True
    Else
        CheckCRC = False
    End If
End Function

在解析电子秤、计米器数据方法的最后调用上面函数 CheckCRC 作为最后一道防线，非法数据不显示到前端，防止解析后的数据不稳定的跳。