Question

我需要帮助读取带有modbus协议的串口告诉我从芯片组读取HEX值，需要在阅读之前发送：

1E 03 00 0C 00 01 46 66 ..

回复示例是：

1E 03 02 xx yy ch cl

Imports System          'To Access Console.WriteLine()
Imports System.IO.Ports 'To Access the SerialPort Object
Module Module1

Sub Main()
    Console.WriteLine(ReceiveSerialData())
    Console.Read()
End Sub

Function ReceiveSerialData() As String
    'modbas
    ' Receive strings from a serial port.
    Dim returnStr As String = ""
    Dim com9 As IO.Ports.SerialPort = Nothing
    Try
        com9 = My.Computer.Ports.OpenSerialPort("COM9")
        com9.ReadTimeout = 5000
        com9.BaudRate = 19200
        com9.Parity = Parity.None
        com9.DataBits = 8
        com9.StopBits = StopBits.One
       ' com9.Write("1E 03 00 0C 00 01 46 66") ' stringa che serve per farsi rispondere dal chip, obbligo di inviarla
        ' com9.Read("1E 03 00 0C 00 01 46 66",0,8)
        Do
            Dim Incoming As String = com9.ReadLine()
            If Incoming Is Nothing Then
                Exit Do
            Else
                returnStr &= Incoming & vbCrLf
            End If
        Loop
    Catch ex As TimeoutException
        returnStr = "Error: Serial Port read timed out."
    Finally
        If com9 IsNot Nothing Then com9.Close()
    End Try
    Return returnStr
End Function

End Module

Answer 1

如果您使用的是Modbus RTU串行协议。如果你是，你不想写一个字符串，你想写原始字节，如：

byte[] request = new byte[]{1E,03,00,0C,00,01,46,66};
com9.Write(request, 0, request.Length);

您还需要读取原始字节。类似的东西：

byte [] response = new byte [256]; com9.Read（回复，0,7）; //＆lt; - count（7）实际上取决于响应包

这不是最佳阅读方式，您可能会收到异常响应等，但它应该可以用于快速测试。

您确定您的COM设置是否正确？按照标准，你应该每个字节发送11位，所以：

1) Even/Odd/Mark parity bit
9600/19200 BAUD
8 data bits
1 Stop Bit

OR

2) No parity bit
9600/19200 BAUD
8 data bits
2 Stop Bits <- an extra stop bit

当然，有些设备支持其他组合。

Vbnet 2017，第一次在modbus上拍摄

1 个答案: