引发异常-从Arduino到Visual Basic接收数据

问题描述

我正在尝试从Arduino发送串行数据并在Visual Basic上读取它。当我执行代码时，有时可以工作，有时不能：抛出异常，System.ArgumentOutOfRangeException：'索引和长度必须引用字符串中的位置。你能帮助我吗？ 我是Visual Basic的新手，谢谢。

Imports System.IO
Imports System.IO.Ports
Imports System.Threading

Public Class Form1
Dim TWSL,TWAL,THL,AoAL,WAL,PeL,RoilL,RyL,RydL As Integer
Dim TWS,TWA,TH,AoA,WA,Pe,Roil,Ry,Ryd,TWSResult,TWAResult,THResult,AoAResult,WAResult,PeResult,RoilResult,RyResult,RydResult As String
Dim StrSerialIn,StrSerialInRam As String

Private Sub Form1_Load(sender As Object,e As EventArgs) Handles MyBase.Load
    Me.CenterToParent()
    SerialPort1.PortName = "COM4"
    SerialPort1.Baudrate = 9600
    SerialPort1.open()
    Timer1.Start()
    SerialPort1.Write(TrackBaraWA.Value & Chr(10))
End Sub

Private Sub Timer1_Tick(sender As Object,e As EventArgs) Handles Timer1.Tick
    Try
        StrSerialIn = SerialPort1.ReadExisting

        Dim TB As New TextBox
        TB.Multiline = True
        TB.Text = StrSerialIn

        If TB.Lines.Count > 0 Then
            If TB.Lines(0) = "Failed to read" Then
                Timer1.Stop()
                SerialPort1.Close()
                Return
            End If

            StrSerialInRam = TB.Lines(0).Substring(0,2)
            If StrSerialInRam = "A" Then
                TWS = TB.Lines(0)
                TWSL = TWS.Length
            Else
                TWS = TWS
            End If

            StrSerialInRam = TB.Lines(1).Substring(0,3)
            If StrSerialInRam = "B" Then
                TWA = TB.Lines(1)
                TWAL = TWA.Length
            Else
                TWA = TWA
            End If

            StrSerialInRam = TB.Lines(2).Substring(0,3)
            If StrSerialInRam = "C" Then
                TH = TB.Lines(2)
                THL = TH.Length
            Else
                TH = TH
            End If

            StrSerialInRam = TB.Lines(3).Substring(0,2)
            If StrSerialInRam = "D" Then
                AoA = TB.Lines(3)
                AoAL = AoA.Length
            Else
                AoA = AoA
            End If

            StrSerialInRam = TB.Lines(4).Substring(0,1)
            If StrSerialInRam = "E" Then
                WA = TB.Lines(4)
                WAL = WA.Length
            Else
                WA = WA
            End If

            StrSerialInRam = TB.Lines(5).Substring(0,3)
            If StrSerialInRam = "F" Then
                Pe = TB.Lines(5)
                PeL = Pe.Length
            Else
                Pe = Pe
            End If

            StrSerialInRam = TB.Lines(6).Substring(0,3)
            If StrSerialInRam = "G" Then
                Roil = TB.Lines(6)
                RoilL = Roil.Length
            Else
                Roil = Roil
            End If

            StrSerialInRam = TB.Lines(7).Substring(0,3)
            If StrSerialInRam = "H" Then
                Ry = TB.Lines(7)
                RyL = Ry.Length
            Else
                Ry = Ry
            End If

            StrSerialInRam = TB.Lines(8).Substring(0,3)
            If StrSerialInRam = "I" Then
                Ryd = TB.Lines(8)
                RydL = Ryd.Length
            Else
                Ryd = Ryd
            End If

            TWSResult = Mid(TWS,2,TWSL)
            TWAResult = Mid(TWA,TWAL)
            THResult = Mid(TH,THL)
            AoAResult = Mid(AoA,AoAL)
            WAResult = Mid(WA,WAL)
            PeResult = Mid(Pe,PeL)
            RoilResult = Mid(Roil,RoilL)
            RyResult = Mid(Ry,RyL)
            RydResult = Mid(Ryd,RydL)

            TWSvalue.Text = TWSResult
            TWAvalue.Text = TWAResult
            THvalue.Text = THResult
            AoAvalue.Text = AoAResult
            WAvalue.Text = WAResult
            PeValue.Text = PeResult
            RoilValue.Text = RoilResult
            RyValue.Text = RyResult
            RydValue.Text = RydResult

解决方法

根据我的收集，您正在尝试从文本框的特定行中的特定位置获取字符。根据您在问题中包含的错误消息，我假设该错误发生在包含“ String。Substring”方法的代码行上。如果从中获取子字符串的字符串太短而无法覆盖您在子字符串方法中指定的范围，则会收到此错误。例如，如果您从第2行开始的子字符串长度为3个字符，且从字符0开始，并且少于3个字符，则会出现此错误。

请参阅有关String.Substring方法here

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