[RESOLVED] [2005] Reading Serial Port

Im currently working on serial port RS232 communication, im able to set configurations thru serial port to my device, but having problems reading from the port. So im posting the same questions in a few VB forum, with the hope to obtain various valuable comments and suggestions..

I'm sending out command in ascii form, for example:

I want to set the "run" state of spectrum analyzer, its command is Q1 CR

therefore, inside a button event handler, i wrote:

Try

SerialPort1.Write(Chr(81) & Chr(49) & Chr(13))

Catch ex As Exception

MsgBox(ex.ToString)

End Try






As for reading from the serial port part, the problems come where, i put the below source codes, and the results is that the value is changing extremely fast like overflow that i cant really read the values measured. The values received from the spectrum analyzer are integer value. like, -70, etc...sometimes the value remain constant... how do i set the timer so that the port will poll for new incoming data at certain interval, say 1second,... and it discards the same incoming value as the present one, and only display an incoming data which is different from present.

But then, im confused because the fast changing figure are not really numbers we can read, instead i get something like, n ? E, etc.. What should i do with them so that i can read the actual value.

Besides, if i want to display the incoming data in an an real time graph, what should i use inside the toolbox?

'Read signals

Private Sub Button8_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button8.Click

SerialPort1.WriteLine(Chr(82) & Chr(51) & Chr(13) & vbCrLf)

End Sub

Private Sub DataReceived( _

ByVal sender As Object, _

ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) _

Handles SerialPort1.DataReceived

TextBox3.Invoke(New _

myDelegate(AddressOf updateTextBox3), _

New Object() {})

End Sub

Public Delegate Sub myDelegate()

Public Sub updateTextBox3()


End Sub





Your help is very much appreciated!

The sub updateTextBox3 is empty?
Try this:

VB Code:

Public Sub updateTextBox3()
 
                TextBox3.AppendText(serialport.ReadLine)
         
    End Sub

This reads up to the NewLine value.
You can specify this value in the serialport settings
eg SerialPort1.NewLine = vbCr
or whatever the terminating character that is used by the analyzer.
Use a multiline textbox to see the exact nature of your incoming data.

Or you could also just read a byte at a time....

VB Code:

Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
 
            'fires when data is received in the input buffer
           If SerialPort1.BytesToRead > 0 Then
              Do
                  updateTextBox3(SerialPort1.ReadByte)
                  If SerialPort1.BytesToRead = 0 Then
                      Exit Do
                  End If 
             Loop
          End If 
       End Sub

Check the format of the bytes you are receiving and convert them to the format that you require.
I am not sure what you want exactly, but if you want to put data into a graph convert the incoming ascii to integer. MSDN help has plenty of information on character formatting etc.

Can I have some comments regarding the codes below. Where the mistakes are? and how to append read data to textbox?


Public Class Form1

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load


If SerialPort1.IsOpen Then
SerialPort1.Close()
End If

Try
With SerialPort1
.PortName = "COM1"
.BaudRate = 9600
.Parity = IO.Ports.Parity.None
.DataBits = 8
.StopBits = IO.Ports.StopBits.Two
End With
SerialPort1.Open()

Catch ex As Exception
MsgBox(ex.ToString)
End Try


End Sub

Dim WithEvents SerialPort As New System.IO.Ports.SerialPort
Dim rxbyte As New ArrayList
Dim i As Integer

Public Delegate Sub myDelegate()

Public Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As _
System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived

If SerialPort1.BytesToRead > 0 Then
Do
rxbyte.Add(SerialPort1.ReadByte)

TextBox1.Invoke(New myDelegate(AddressOf updateTextBox1), _
New Object() {SerialPort1.ReadByte})

Exit Do
Loop
End If
End Sub

Public Sub updateTextBox1()

With TextBox1
.AppendText(rxbyte(i))
End With

End Sub


End Class

In the DataReceived event sub you need to change to this....

VB Code:

TextBox1.Invoke(New myDelegate(AddressOf updateTextBox1), _ 
              New Object() {})

and also this....

VB Code:

Public Sub updateTextBox1()
 
          Dim i As Integer
          For i = 0 To rxbyte.Count - 1 
             With TextBox1
                  'Option Strict On
                  'CInt to convert Objects in arraylist to integer.       
                  'Chr to convert the integers into Ascii characters
                  .AppendText(Chr(CInt(rxbyte(i))))
              End With 
         Next
        End Sub

everything should work correctly now.
hope this helps.

thanks but i still cant read..
From my device, which is spectrum analyzer manual, i have some reading data command, but i wonder how to write the command so that the data reading event can read. and does it affect the data reading event? hereby include the url of reading output level for my device:

http://www.geocities.com/sandrea83/3...32commands.doc

Here's a suggestion... open Hyper Terminal, connect to the device and try some simple command first such as R1 and see if you can get any response from the device. If there's no response whatsoever, either your com port settings are incorrect or the command wasn't understood by the device or the device is malfunctioning. If you can communicate with the device via hyper terminam, there is'nt any reason why you can't in your program.

im confused what a hyper terminal is actually ? and how to use it? if i were to program it to read based on those commands inside the word file, what should i do? put those command in write command inside the event handler of a button? or write it inside DataReceived event?

Quote:

---

Originally Posted by wence

im confused what a hyper terminal is actually ? and how to use it? if i were to program it to read based on those commands inside the word file, what should i do? put those command in write command inside the event handler of a button? or write it inside DataReceived event?

---

HyperTerminal is a software come bundled with the OS. If you're running WinXP, your can start it by:
Start > All Programs > Accessories > Communications > Hyper Terminal
Open it up, enter in necessary parameters for port settings and connect.
Once connected, you can type in commands to send to your device and it will display any response back on the screen ... sort of like a chat window.

Now to answer your second question: if you have your command stored in a text file, you can use StreamReader class to read the file into an array, then refer to the appropriate element in this array to send your command. However, it can get messy because you will have to keep track of which command stored in what element. Another suggest is to declare your commands as constant variables with thin your program at class level, so that when you want to send a command, you just use the variable. Something like:

VB Code:

Private Const Cmd1 As String = "R1"
    Private Const Cmd2 As String = "R2" & ChrW(13) & "W0"
    '........ blablabla ......

Then later on when you want to send a command to the device, just use Cmd1, Cmd2, ...
However, your top priority is to get the thing to work... Once you get the communication established, you can always fine tune your app later.

thanks stanav,ill try wif hyper terminal next week...i dont hav problem wif writing to the port, but reading data is a problem..therere in fact a few commands for read data...wonder where should i put my command for reading data?
for example, to send a command to read data: SerialPort1.WriteLine(Chr(82) & Chr(51) & Chr(13))

VB Code:

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
SerialPort1.WriteLine(Chr(82) & Chr(51) & Chr(13))
end sub

or

Public Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As _
System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
SerialPort1.WriteLine(Chr(82) & Chr(51) & Chr(13))
end sub

so far ive tried put such command inside the event handler of a button but eventually the device hang..

Hi,

This link could be usefull, about reading serial port;

http://msdn.microsoft.com/library/de...onnections.asp

Wkr,

sparrow1

Quote:

---

Originally Posted by wence

thanks stanav,ill try wif hyper terminal next week...i dont hav problem wif writing to the port, but reading data is a problem..therere in fact a few commands for read data...wonder where should i put my command for reading data?
for example, to send a command to read data: SerialPort1.WriteLine(Chr(82) & Chr(51) & Chr(13))

VB Code:

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
SerialPort1.WriteLine(Chr(82) & Chr(51) & Chr(13))
end sub

or

Public Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As _
System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
SerialPort1.WriteLine(Chr(82) & Chr(51) & Chr(13))
end sub

so far ive tried put such command inside the event handler of a button but eventually the device hang..

---

It really depends on how you want to read the data from your device. To make it a little more clear to you, in order to read the device's data, you have to tell it to give you the data. That's why you have to send the commands to the device. Although there are devices that automatically send out data, communication is only 1-way, such as most telephone switch systems and all you have to do is read the data at your convenience on these devices, however I don't think your device belongs to this group.
Now back to your questtion, there are basically 2 ways to read data from a device: timed interval or continuous. For timed interval reading, you can use a timer, and send a command at the timer_tick event. For continuous reading, in your form load event, after open your comport, send a command. Then in your updateTextbox sub, after reading any data returned, you want to send a command to the device again. This will create an infinite loop of send and receive asynchronously.

Hi Stanav,thanks for your advices. i think my program got problem on the datareceived part. this morning, i try with hyperminal, it works. For example,i set a certain mark frequency in my device, then i write a command "L0 CR" to the serial port, then i disconnect COM1 at my program, connect COM1 at the hyperterminal instead, the hyperterminal screen read the frequency value which i set earlier, like 1223.444. Although i not able to read to the signal strength value yet.
So hyperterminal is only for reading, and you cant write to device using hyperterminal? What would be the biggest problem if hyperterminal reads but my program doesnt?

thanks..

Quote:

---

Originally Posted by wence

Hi Stanav,thanks for your advices. i think my program got problem on the datareceived part. this morning, i try with hyperminal, it works. For example,i set a certain mark frequency in my device, then i write a command "L0 CR" to the serial port, then i disconnect COM1 at my program, connect COM1 at the hyperterminal instead, the hyperterminal screen read the frequency value which i set earlier, like 1223.444. Although i not able to read to the signal strength value yet.
So hyperterminal is only for reading, and you cant write to device using hyperterminal? What would be the biggest problem if hyperterminal reads but my program doesnt?

thanks..

---

Hello Wence,
Try this code. It's taken from one of my working apps. I trimmed it a bit so that it only contains relevant code for serial port stuff. You can modify it to send different commands according to your needs.

VB Code:

'don't for get to put "Imports System.IO.Ports" at top of the code page
 
    'Declare a comport object with class level scope
    Private WithEvents comPort As New IO.Ports.SerialPort
 
    'In form_load, open comport
    Private Sub frmMain_Load(ByVal sender As System.Object, _
                     ByVal e As System.EventArgs) Handles MyBase.Load
        OpenComPort()
        'Then send request to read data
        SendRequestCommand("L0" & ChrW(13))  'Modify your command string as needed
 
    End Sub
    Private Sub OnDataReceived(ByVal sender As Object, _
                    ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) _
                    Handles comPort.DataReceived
        Try
         txtDataReceived.Invoke(New myDelegate(AddressOf UpdateTextBox), New Object() {})
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End Sub
 
    'This is the delegate used to invoke your updateTextBox sub
    Public Delegate Sub myDelegate()
 
    Public Sub UpdateTextBox()
        Dim strInData As String = ""
        'Read one byte at a time
        While comPort.BytesToRead > 0 
            strInData &= ChrW(comPort.ReadByte())
        End While
        'Do whatever you want with the data
        txtDataReceived.Text = strInData
        txtDataReceived.Refresh()
        System.Threading.Thread.Sleep(100)
        SendRequestCommand("L0" & ChrW(13)) 'Again, change the command to fit your need.
    End Sub
   
    Private Sub OpenComPort()
            CloseComPort()            
            Try
                'Initialize com port. You need to substitute these settings with the correct parameters for your device
                With comPort
                    .PortName = "COM1"
                    .BaudRate = 9600
                    .Parity = IO.Ports.Parity.Odd
                    .DataBits = 7
                    .StopBits = IO.Ports.StopBits.Two
                    .ReadBufferSize = 64
                    .ReadTimeout = 500
                    .ReceivedBytesThreshold = 5 'Adjust this settings according to
                    ' the expected length of the returned data. You can play with 
                    ' it a bit to get optimized performance.
                    .Handshake = IO.Ports.Handshake.None
                    .RtsEnable = True
                    .DtrEnable = True
                    .Encoding = System.Text.Encoding.ASCII
                End With
                'Open com port
                comPort.Open()
            Catch ex As Exception
                MsgBox(ex.Message)
            End Try
     End Sub
        
     Private Sub CloseComPort()
        If comPort.IsOpen() Then
            comPort.Close()
        End If
    End Sub
    
    Private Sub SendRequestCommand(ByVal cmd As String)
        If comPort.IsOpen() Then
            comPort.DiscardInBuffer()
            comPort.Write(cmd)
        Else
            MsgBox("COM port is closed!")
        End If
    End Sub

Hope this helps.

thanks lots stanav. I'll try on it.

Hi Stanav, i really appreciate your help. It works! I can display the frequency which i set in the device on the textbox. However, i still cant read the signal measured by the device. I can see that the serialport1.readbyte command has to come in the updatetextbox sub, not in the datareceived event.

I have a few question here:
1) What does these commands mean:
comPort.DiscardInBuffer()
and why has to be &= instead of = only?

2)Is it possible i put different textboxs and display different data received from the device all at the same time?

3)I try a function which is data memory output copy wif hyper terminal. and as a result, i get a whole content in characters which i dont understand, the character font is terminal if not mistaken. and i wonder why i could read the set frequency value straight away wif ht, but not wif the data memory i get?


Regards...