通过 COM 从秤中请求重量值

Question

我一直在尝试使用 COM 串行端口从两个不同的秤中检索重量值。

天平是 CAS ER Plus 和 UWE AM-15K。

我已经设法创建了一个小程序来启动 PC 和 Scales 之间的通信，但我运行遇到了一个问题，我一直找不到解决方案。

我可以发送 ENQ 命令并从两个秤成功接收到 ACK，但是当我发送 DC1 命令检索重量时，我总是从消息中得到各种变化

"Hex number must be smaller than 7fffffffffffffff"

和

"Hex Value Must be Maximum Length of 32 characters."

我配置 COM 端口的代码如下：

Try
        comport.PortName = "COM1"
        comport.BaudRate = 9600
        comport.Parity = Parity.None
        comport.DataBits = 8
        comport.StopBits = StopBits.One
        comport.Handshake = Handshake.XOnXOff
        If DTRCheck.Checked Then
            comport.DtrEnable = True
        End If
        If RTSCheck.Checked Then
            comport.RtsEnable = True
        End If
        'Dim encoding As System.Text.Encoding = System.Text.Encoding.GetEncoding("IBM860")
        Dim encoding As System.Text.Encoding = System.Text.Encoding.ASCII
        comport.Encoding = encoding
        comport.Open()
        erroCOM = False
    Catch ex As Exception
        erroCOM = True
    End Try

我发送命令的代码：

 If comport.IsOpen Then
        TxtValor.Clear()
        Try
            If EnqComBtn.Checked Then 'Verify if the scale is "listening"
                ListBox1.Items.Add("PC: ENQ - >")
                comport.Write(New Byte() {&H5}, 0, 1)
                Thread.Sleep(20)
                ListBox1.Items.Add("PC: DC1 - >")
                comport.Write(New Byte() {&H11}, 0, 1)
            End If
            If DC1ComBtn.Checked Then 'Request weight value
                ListBox1.Items.Add("PC: DC1 - >")
                comport.Write(New Byte() {&H11}, 0, 1)
                Thread.Sleep(20)
            End If
        Catch ex As Exception

        End Try

    End If

发送命令后，我让程序从 COM 串行端口读取通过 DataReceived 事件接收到的值，并将十六进制值转换为十进制值。

编辑：

这是我用来读取接收到的字节并将其从字节转换为十六进制的代码。我在 Whosebug 上的另一个 post 上找到了这段代码，并编辑了空格部分。

Private Sub comport_DataReceived(sender As Object, e As SerialDataReceivedEventArgs) 句柄 comport.DataReceived

    Dim RXByte As Byte
    Do
        RXCnt = 0
        Do
            RXByte = comport.ReadByte
            RXArray(RXCnt) = LookUpTable(RXByte >> 4) ' Convert each byte to two hexadecimal characters 
            RXCnt = RXCnt + 1
            RXArray(RXCnt) = LookUpTable(RXByte And 15)
            RXCnt = RXCnt + 1
        Loop Until (comport.BytesToRead = 0)
        '----- End of communication protocol handling ------------------------------------------------------------- 

        Me.Invoke(New MethodInvoker(AddressOf Display)) ' Start "Display" on the UI thread 

    Loop Until (comport.BytesToRead = 0)  ' Don't return if more bytes have become available in the meantime 

End Sub

有没有人以前发现过这个问题，如果有，你找到解决方案了吗？谢谢！

Answer 1

我找到了解决问题的方法！

问题是我正在逐字节读取 BytesToRead，我必须执行 ReadExisting。

前一个代码：

Dim RXByte As Byte
    'Dim RXBytes() As Byte
    Dim bytString As String = ""
    Do
        RXCnt = 0
        Do
            RXByte = comport.ReadByte
            RXArray(RXCnt) = LookUpTable(RXByte >> 4) ' Convert each byte to two hexadecimal characters 
            RXCnt = RXCnt + 1
            RXArray(RXCnt) = LookUpTable(RXByte And 15)
            RXCnt = RXCnt + 1
        Loop Until (comport.BytesToRead = 0)
        '----- End of communication protocol handling ------------------------------------------------------------- 

    Me.Invoke(New MethodInvoker(AddressOf Display)) ' Start "Display" on the UI thread 

    Loop Until (comport.BytesToRead = 0)  ' Don't return if more bytes have become available in the meantime

解决方案：

RXValue = ""

    Try

        RXValue = comport.ReadExisting()
        If RXValue <> "" Then
            Me.Invoke(New MethodInvoker(AddressOf Display)) ' Start "Display" on the UI thread 
        Else

        End If
    Catch ex As Exception

    End Try

希望对遇到同样问题的人有所帮助！

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