How to read data from serial port in vb.net? - vb.net

Question

I made a class and there is this sub named SendUSSD, when this is called it sends a ussd code like *123# to a COM port where a gsm mobile is connected. This ussd is supposed to return the mobile balance.
If IsOpen = True Then 'checks if the port is open
SMSPort.WriteLine("AT+CUSD=1,""*123#""" vbCr) 'this sends the ussd code
Form1.TextBox2.Text = SMSPort.ReadLine().ToString() 'this shows the response
End If
Now the problem is sometimes I get the full response like "Your current balance is so and so". But, most of the time I get a part of the message like "Your curr". My guess is that it takes some time to get the response, so how do I make this Form1.TextBox2.Text = SMSPort.ReadLine().ToString() line wait until the last character which is a full-stop to appear and then execute the line?

Answer 1

im using this class to connect com ports.
'connect like this
Public comm As New CommunicationManager
comm.Parity = "None"
comm.StopBits = "One"
comm.DataBits = "8"
comm.BaudRate = "38400"
comm.PortName = comport_ismi
comm.OpenPort()
and the class
Imports System.Text
Imports System.Drawing
Imports System.IO.Ports
Imports System.Windows.Forms
Public Class CommunicationManager
#Region "Manager Enums"
''' <summary>
''' enumeration to hold our transmission types
''' </summary>
Public Enum TransmissionType
Text
Hex
End Enum
''' <summary>
''' enumeration to hold our message types
''' </summary>
Public Enum MessageType
Incoming
Outgoing
Normal
Warning
[Error]
End Enum
#End Region
#Region "Manager Variables"
'property variables
Private _baudRate As String = String.Empty
Private _parity As String = String.Empty
Private _stopBits As String = String.Empty
Private _dataBits As String = String.Empty
Private _portName As String = String.Empty
Private _transType As TransmissionType
Private _displayWindow As RichTextBox
'global manager variables
Private MessageColor As Color() = {Color.Blue, Color.Green, Color.Black, Color.Orange, Color.Red}
Private comPort As New SerialPort()
#End Region
#Region "Manager Properties"
''' <summary>
''' Property to hold the BaudRate
''' of our manager class
''' </summary>
Public Property BaudRate() As String
Get
Return _baudRate
End Get
Set(value As String)
_baudRate = value
End Set
End Property
''' <summary>
''' property to hold the Parity
''' of our manager class
''' </summary>
Public Property Parity() As String
Get
Return _parity
End Get
Set(value As String)
_parity = value
End Set
End Property
''' <summary>
''' property to hold the StopBits
''' of our manager class
''' </summary>
Public Property StopBits() As String
Get
Return _stopBits
End Get
Set(value As String)
_stopBits = value
End Set
End Property
''' <summary>
''' property to hold the DataBits
''' of our manager class
''' </summary>
Public Property DataBits() As String
Get
Return _dataBits
End Get
Set(value As String)
_dataBits = value
End Set
End Property
''' <summary>
''' property to hold the PortName
''' of our manager class
''' </summary>
Public Property PortName() As String
Get
Return _portName
End Get
Set(value As String)
_portName = value
End Set
End Property
''' <summary>
''' property to hold our TransmissionType
''' of our manager class
''' </summary>
Public Property CurrentTransmissionType() As TransmissionType
Get
Return _transType
End Get
Set(value As TransmissionType)
_transType = value
End Set
End Property
''' <summary>
''' property to hold our display window
''' value
''' </summary>
Public Property DisplayWindow() As RichTextBox
Get
Return _displayWindow
End Get
Set(value As RichTextBox)
_displayWindow = value
End Set
End Property
#End Region
#Region "Manager Constructors"
''' <summary>
''' Constructor to set the properties of our Manager Class
''' </summary>
''' <param name="baud">Desired BaudRate</param>
''' <param name="par">Desired Parity</param>
''' <param name="sBits">Desired StopBits</param>
''' <param name="dBits">Desired DataBits</param>
''' <param name="name">Desired PortName</param>
Public Sub New(baud As String, par As String, sBits As String, dBits As String, name As String, rtb As RichTextBox)
_baudRate = baud
_parity = par
_stopBits = sBits
_dataBits = dBits
_portName = name
_displayWindow = rtb
'now add an event handler
AddHandler comPort.DataReceived, New SerialDataReceivedEventHandler(AddressOf comPort_DataReceived)
End Sub
''' <summary>
''' Comstructor to set the properties of our
''' serial port communicator to nothing
''' </summary>
Public Sub New()
_baudRate = String.Empty
_parity = String.Empty
_stopBits = String.Empty
_dataBits = String.Empty
_portName = comport_ismi
_displayWindow = Nothing
'add event handler
AddHandler comPort.DataReceived, New SerialDataReceivedEventHandler(AddressOf comPort_DataReceived)
End Sub
#End Region
#Region "WriteData"
Public Sub WriteData(msg As String)
Select Case CurrentTransmissionType
Case TransmissionType.Text
'first make sure the port is open
'if its not open then open it
If Not (comPort.IsOpen = True) Then
comPort.Open()
End If
'send the message to the port
comPort.Write(msg)
'display the message
DisplayData(MessageType.Outgoing, msg & Convert.ToString(vbLf))
Exit Select
Case TransmissionType.Hex
Try
'convert the message to byte array
Dim newMsg As Byte() = HexToByte(msg)
'send the message to the port
comPort.Write(newMsg, 0, newMsg.Length)
'convert back to hex and display
DisplayData(MessageType.Outgoing, ByteToHex(newMsg) & Convert.ToString(vbLf))
Catch ex As FormatException
'display error message
DisplayData(MessageType.[Error], ex.Message)
Finally
_displayWindow.SelectAll()
End Try
Exit Select
Case Else
'first make sure the port is open
'if its not open then open it
If Not (comPort.IsOpen = True) Then
comPort.Open()
End If
'send the message to the port
comPort.Write(msg)
'display the message
DisplayData(MessageType.Outgoing, msg & Convert.ToString(vbLf))
Exit Select
End Select
End Sub
#End Region
#Region "HexToByte"
''' <summary>
''' method to convert hex string into a byte array
''' </summary>
''' <param name="msg">string to convert</param>
''' <returns>a byte array</returns>
Private Function HexToByte(msg As String) As Byte()
'remove any spaces from the string
msg = msg.Replace(" ", "")
'create a byte array the length of the
'divided by 2 (Hex is 2 characters in length)
Dim comBuffer As Byte() = New Byte(msg.Length / 2 - 1) {}
'loop through the length of the provided string
For i As Integer = 0 To msg.Length - 1 Step 2
'convert each set of 2 characters to a byte
'and add to the array
comBuffer(i / 2) = CByte(Convert.ToByte(msg.Substring(i, 2), 16))
Next
'return the array
Return comBuffer
End Function
#End Region
#Region "ByteToHex"
''' <summary>
''' method to convert a byte array into a hex string
''' </summary>
''' <param name="comByte">byte array to convert</param>
''' <returns>a hex string</returns>
Private Function ByteToHex(comByte As Byte()) As String
'create a new StringBuilder object
Dim builder As New StringBuilder(comByte.Length * 3)
'loop through each byte in the array
For Each data As Byte In comByte
'convert the byte to a string and add to the stringbuilder
builder.Append(Convert.ToString(data, 16).PadLeft(2, "0"c).PadRight(3, " "c))
Next
'return the converted value
Return builder.ToString().ToUpper()
End Function
#End Region
#Region "DisplayData"
''' <summary>
''' method to display the data to & from the port
''' on the screen
''' </summary>
''' <param name="type">MessageType of the message</param>
''' <param name="msg">Message to display</param>
<STAThread> _
Private Sub DisplayData(type As MessageType, msg As String)
'_displayWindow.Invoke(New EventHandler(Sub()
' _displayWindow.SelectedText = String.Empty
' _displayWindow.SelectionFont = New Font(_displayWindow.SelectionFont, FontStyle.Bold)
' _displayWindow.SelectionColor = MessageColor(CInt(type))
' _displayWindow.AppendText(msg)
' _displayWindow.ScrollToCaret()
' End Sub))
End Sub
#End Region
#Region "OpenPort"
Public Function OpenPort() As Boolean
Try
'first check if the port is already open
'if its open then close it
If comPort.IsOpen = True Then
comPort.Close()
End If
'set the properties of our SerialPort Object
comPort.BaudRate = Integer.Parse(_baudRate)
'BaudRate
comPort.DataBits = Integer.Parse(_dataBits)
'DataBits
comPort.StopBits = DirectCast([Enum].Parse(GetType(StopBits), _stopBits), StopBits)
'StopBits
comPort.Parity = DirectCast([Enum].Parse(GetType(Parity), _parity), Parity)
'Parity
comPort.PortName = _portName
'PortName
'now open the port
comPort.Open()
'display message
DisplayData(MessageType.Normal, "Port AÇILDI: " + DateTime.Now + vbLf)
'return true
Return True
Catch ex As Exception
DisplayData(MessageType.[Error], ex.Message)
Return False
End Try
End Function
#End Region
#Region "ClosePort"
Public Function ClosePort() As Boolean
Try
'first check if the port is already open
'if its open then close it
If comPort.IsOpen = True Then
comPort.Close()
End If
'display message
DisplayData(MessageType.Normal, "Port KAPANDI: " + DateTime.Now + vbLf)
'return true if port is closed
If comPort.IsOpen = False Then
Return True
End If
DisplayData(MessageType.Normal, "Kapatmada hata oluştu" & vbLf)
Return False
Catch ex As Exception
DisplayData(MessageType.[Error], ex.Message)
Return False
End Try
End Function
#End Region
#Region "SetParityValues"
Public Sub SetParityValues(obj As Object)
For Each str As String In [Enum].GetNames(GetType(Parity))
DirectCast(obj, ComboBox).Items.Add(str)
Next
End Sub
#End Region
#Region "SetStopBitValues"
Public Sub SetStopBitValues(obj As Object)
For Each str As String In [Enum].GetNames(GetType(StopBits))
DirectCast(obj, ComboBox).Items.Add(str)
Next
End Sub
#End Region
#Region "SetPortNameValues"
Public Sub SetPortNameValues(obj As Object)
For Each str As String In SerialPort.GetPortNames()
DirectCast(obj, ComboBox).Items.Add(str)
Next
End Sub
#End Region
#Region "comPort_DataReceived"
''' <summary>
''' method that will be called when theres data waiting in the buffer
''' </summary>
''' <param name="sender"></param>
''' <param name="e"></param>
Private Sub comPort_DataReceived(sender As Object, e As SerialDataReceivedEventArgs)
'determine the mode the user selected (binary/string)
Select Case CurrentTransmissionType
'user chose string
Case TransmissionType.Text
'read data waiting in the buffer
Dim msg As String = comPort.ReadExisting()
'display the data to the user
DisplayData(MessageType.Incoming, msg)
' + "\n"); **************
Exit Select
'user chose binary
Case TransmissionType.Hex
'retrieve number of bytes in the buffer
Dim bytes As Integer = comPort.BytesToRead
'create a byte array to hold the awaiting data
Dim comBuffer As Byte() = New Byte(bytes - 1) {}
'read the data and store it
comPort.Read(comBuffer, 0, bytes)
'display the data to the user
DisplayData(MessageType.Incoming, ByteToHex(comBuffer))
' + "\n");
Exit Select
Case Else
'read data waiting in the buffer
Dim str As String = comPort.ReadExisting()
'display the data to the user
DisplayData(MessageType.Incoming, str)
' + "\n");
Exit Select
End Select
End Sub
#End Region
End Class

Answer 2

I guess you are using the DataReceived event, if so, you can just take the data and split it by the lastIndexOf(Enviroment.NewLine).
you will have two part the first one is a string with some amount of lines and the second one is a string that contain no more lines.
You can take the first part and split it by new line and even create a new event (LineReceived).
for the second part(the part after the lastIndexOf(Enviroment.NewLine)) of the data just concatenate it to the beginning of the data that will arrive the next time.

Answer 3

Try setting comm.Newline. Probably should be vbCR.