[RESOLVED] read string from COM1 without MSCOMM

[dhell]

Hello all VB masters,
I'm a VERY VERY newbie in VB, but I got a very difficult task
I need to read string from serial port (COM1), and for some reason, I can't use MSCOMM component . I already search the internet for the answer but still I stuck. Here is some code I've made :


fCOM = FreeFile
Dim LineText As String

Open "COM6" For Input As #fCOM
LineText = fCOM

Close #fCOM
Text1.Text = Text1.Text + LineText




but what I've got is just "1" character on my text1 component. Any suggestion from masters?
Thanks for read my post

[Milk]

I don't know much about serial port communication but I'm pretty sure you can't access it as you are (Open Com is QBasic) Besides the reason why you just read a "1" is because that is the file number that FreeFile has returned, it is not coming from "COM6" which VB would interpret as a file name anyway.

If you can't use the MSCOMM component then I think there are API's that will work.

Here's some more info.

[Hack]

Welcome to the forums.

and for some reason, I can't use MSCOMM component

Why not? Did you try and get errors?

[CDRIVE]

As far as I know MSComm was included in the Pro & Enterprise editions only. What VB version do you have?

[dhell]

Thanks for all reply,
milk : Thanks for the article and 780 pdf pages but I can't find any related topic there. Thanks anyway, I really apreciate it.
hack : because the task has to do that way, I'm not allow to use any component for my code
cdrive : I'm not sure which VB editions, but I can use MSCOMM component if I want to, the component available on my VB (but I have to do the code without any components )

For additional information, I can send some string to my serial device with this code :

fCOM = FreeFile
 
Open "COM6" For Output As #fCOM
Write #fCOM,"Hello World"
 
Close #fCOM

Hope any one can help...

[CDRIVE]

I'm not sure which VB editions, but I can use MSCOMM component if I want to, the component available on my VB (but I have to do the code without any components )

This sounds like a school project but I can't make any sense of it. How can you write CommControl code without a CommControl on your Form? maybe I'm misunderstanding your statement? Is your instructor allowing CommControl but no other controls???

[dhell]

thanks for reply cdrive,
I'm not allowed even 1 component to do the code. but I think it is make sense because I can send "hello world" string to my serial device, the code is in my previous post. And it works 100 %.
I'm sorry but correct me if I'm wrong, components are build from VB code too, right? so if it works with component, if I write the code (code to make the components) from the component manually, it sure will work too? correct?
Thanks anyway, I'm still hoping someone could help me

[CDRIVE]

thanks for reply cdrive,
I'm not allowed even 1 component to do the code. but I think it is make sense because I can send "hello world" string to my serial device, the code is in my previous post. And it works 100 %.
I'm sorry but correct me if I'm wrong, components are build from VB code too, right? so if it works with component, if I write the code (code to make the components) from the component manually, it sure will work too? correct?
Thanks anyway, I'm still hoping someone could help me

Well, I don't know why you think you're building controls with the code you posted. What you're doing is treating the serial port as a File. While your code does output data from the serial port I don't see how your going to have any flow control or any of the necessary properties required for practical serial com. I did find your code novel though. I don't find it very practical though, except as an exercise. Doogle has expertise with serial com. Perhaps he can help you. He usually answers comm questions.

Btw, if it works 100% of the time then what is your problem?

[CDRIVE]

For additional information, I can send some string to my serial device with this code :

fCOM = FreeFile
 
Open "COM6" For Output As #fCOM
Write #fCOM,"Hello World"
 
Close #fCOM

Hope any one can help...

I ran your code last night and fed it back through a NullModem to another serial port. I then read the results in Hyper Terminal. Needless to say, "Hello World" was not what was displayed. What was displayed was non keyboard character sets. What is the serial device that you're sending your output to? Are both the TX & RX ports open when you read "1" on the RX port?

[dhell]

thanks again cdrive,
I think you got me wrong, what I posted is code for sending string, and my problem is to receive some string from serial port. I just want to prove that I can communicate through serial port without MSCOMM component(but I can only do the sending part )
I tested the code using the Virtual Serial Port software, that's why in my code I use COM6, because the virtual port software create COM6 as virtual port.
About TX and RX, I don't really understang about it, I just use the code and it works
Btw, I've tried with hyper terminal too, but my application always show error when both my application and hyper terminal are activated. And just for additional information, HyperTerminal can communicate perfectly with Virtual Serial Port software.

Doogle heeellllppp..........
(hope he hear me )

[Milk]

<Re MSCOMM> I'm sorry but correct me if I'm wrong, components are build from VB code too, right?

Although probably written in VB it's much more likely it acts as a wrapper for the Api functions as posted in #2 (VB examples for which are given from page 300 in the article, unfortunately truncated).
However it does seem I was wrong and you can do what you want with the File Input/Output commands as per the old QBasic methods. There's apparently an example bas module that came with QBasic called Terminal.bas which demos this and should convert fairly easily to VB. And there's this at MSDN, see the first question in 'Hints and Suggestions', it's for QBasic but it still applies.

It might also be worth your while researching working with text files in VB, you will find many examples of this which can be applied to you comm port.

[CDRIVE]

I don't know where to begin here. I still have QB4.5 on all my machines & I'm familiar with Terminal.BAS. QB used the PRINT not the Write statement to output to the comport. It also required the same arguments in the Open Comm command as VB except LEN. You can see this here.

' Code from QB4.5 "TERMINAL.BAS"
' Open communications (1200 baud, no parity, 8-bit data,
' 1 stop bit, 256-byte input buffer):
OPEN "COM1:1200,N,8,1" FOR RANDOM AS #1 LEN = 256

PRINT #1, KeyInput$;    ' User pressed a key, send the character typed to the modem.

As far as I'm concerned, I think VB has no idea that it's accessing a Comport. Like I said earlier, I suspect that VB thinks it's opening a file. In fact, if you put your code in the Form.Click event and Rem out 'Close #fCOM' I will guarantee you that clicking the Form more than once will return Run Time Error 55 "File Already Open". If VB knew it was communicating with a port you would receive Error 8005 "Port Already Open". I'm not an MSComm expert but I've used it enough to be familiar with the basics.

Now I don't know if Milk is correct, that your code may be intended to be used with an API, or not, so I'm going to stay away from that discussion.

[dhell]

You both are right, that command is usually use to dealing with textfile. I already tried my read command to read textfile before and it worked. That's why I don't think my code is wrong.

Open "C:\test.txt" For Input As #fCOM

but when I change the textfile name to "COM6" you know what happened...

cdrive: about the error message, you are absolutely right, that error message appear when 'Close #fCOM' is removed. I already try it before too

That's why I join this forum, because I almost desperate hehehehe

[Doogle]

I've just found this thread, but I'm not going to be of much use. I've never heard of anyone ever trying to access the Comm ports using standard VB I/O, let alone a not-so-experienced programmer. As Cdrive has mentioned, there are a set of APIs available which the Comm control wraps up, including:

CreateFile - to obtain a handle to the Comm Port
GetCommState - to get the current settings of the Port
SetCommState - to set the settings of the Port
GetCommTimeouts - to get the current timeout values
SetCommTimeouts - to set the timeout values
WriteFile - to output to the Comm Port
ReadFile - to read from the comm Port

I doubt very much that your teacher or whoever is expecting this sort of code from you, I wouldn't expect a 'novice' programmer to be capable of doing this with APIs. It's difficult enough to create a reliable serial port communications program using the MSComm control. I think you should check back with whoever set you this challenge and ask them exactly how they expect you to complete it.

Anyway, there's a reasonable example of using the APIs in .NET here: http://support.microsoft.com/kb/823179 which I have (hopefully) converted to VB. There may be some errors as I haven't got the facilities to test it. All I can say is that it does compile cleanly,

Option Explicit

Private Type COMMTIMEOUTS
        ReadIntervalTimeout As Long
        ReadTotalTimeoutMultiplier As Long
        ReadTotalTimeoutConstant As Long
        WriteTotalTimeoutMultiplier As Long
        WriteTotalTimeoutConstant As Long
End Type

Private Type DCB
        DCBlength As Long
        BaudRate As Long
        fBitFields As Long 'See Comments in Win32API.Txt
        wReserved As Integer
        XonLim As Integer
        XoffLim As Integer
        ByteSize As Byte
        Parity As Byte
        StopBits As Byte
        XonChar As Byte
        XoffChar As Byte
        ErrorChar As Byte
        EofChar As Byte
        EvtChar As Byte
        wReserved1 As Integer 'Reserved; Do Not Use
End Type

Private Type SECURITY_ATTRIBUTES
        nLength As Long
        lpSecurityDescriptor As Long
        bInheritHandle As Long
End Type

Private Const GENERIC_READ As Long = &H80000000
Private Const GENERIC_WRITE As Long = &H40000000
Private Const OPEN_EXISTING As Long = 3
Private Const FILE_ATTRIBUTE_NORMAL As Long = &H80
Private Const NOPARITY As Long = 0
Private Const ONESTOPBIT As Long = 0

Private Declare Function CreateFile Lib "kernel32.dll" Alias "CreateFileA" _
            (ByVal lpFileName As String, ByVal dwDesiredAccess As Long, _
             ByVal dwShareMode As Long, ByRef lpSecurityAttributes As SECURITY_ATTRIBUTES, _
             ByVal dwCreationDisposition As Long, ByVal dwFlagsAndAttributes As Long, _
             ByVal hTemplateFile As Long) As Long

Private Declare Function GetCommState Lib "kernel32.dll" (ByVal nCid As Long, _
            ByRef lpDCB As DCB) As Boolean

Private Declare Function SetCommState Lib "kernel32.dll" (ByVal nCid As Long, _
            ByRef lpDCB As DCB) As Boolean

Private Declare Function GetCommTimeouts Lib "kernel32.dll" (ByVal hFile As Long, _
            ByRef lpCommTimeouts As COMMTIMEOUTS) As Boolean

Private Declare Function SetCommTimeouts Lib "kernel32.dll" (ByVal hFile As Long, _
            ByRef lpCommTimeouts As COMMTIMEOUTS) As Boolean

Private Declare Function WriteFile Lib "kernel32.dll" (ByVal hFile As Long, _
            ByVal lpBuffer As Any, ByVal nNumberOfBytesToWrite As Long, _
            ByRef lpNumberOfBytesWritten As Long, ByVal lpOverlapped As Long) As Boolean

Private Declare Function ReadFile Lib "kernel32.dll" (ByVal hFile As Long, _
            ByVal lpBuffer As Any, ByVal nNumberOfBytesToRead As Long, _
            ByRef lpNumberOfBytesRead As Long, ByVal lpOverlapped As Long) As Boolean

Private Declare Function CloseHandle Lib "kernel32.dll" (ByVal hObject As Long) As Boolean

Private udtTimeOut As COMMTIMEOUTS
Private udtDCB As DCB
Private udtSec As SECURITY_ATTRIBUTES
Private lngHandle As Long

Private Sub cmdReceive_Click()
Dim lngReturn As Long
Dim strMessage As String
Dim lngReceived As Long
Dim lngMaxLen As Long
'
' Maximum number of bytes to be received = 1024
'
lngMaxLen = 1024
strMessage = Space(lngMaxLen)
lngReceived = ReadFile(lngHandle, strMessage, lngMaxLen, lngReceived, 0&)
If lngReceived <> 0 Then
    MsgBox (Left(strMessage, lngReceived))
Else
    MsgBox "Unable to Read from Comm Port " & Err.LastDllError
End If
End Sub

Private Sub cmdSend_Click()
Dim lngReturn As Long
Dim lngWritten As Long
Dim strMessage As String
strMessage = "This is going to be written to the Serial Port"
lngReturn = WriteFile(lngHandle, strMessage, Len(strMessage), lngWritten, 0&)
If lngReturn = 0 Then
    MsgBox "Unable to Write to Comm Port " & Err.LastDllError
End If
End Sub

Private Sub Form_Load()
Dim lngReturn As Long
udtSec.nLength = Len(udtSec)
'
' Open Comm Port 1
'
lngHandle = CreateFile("COM1", GENERIC_READ Or GENERIC_WRITE, 0, udtSec, _
            OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0&)
If lngHandle <> 0 Then
    lngReturn = GetCommState(lngHandle, udtDCB)
    If lngReturn <> 0 Then
        '
        ' Port settings: (9600 Baud, No Parity, 8 Data Bits, 1 Stop Bit
        '
        udtDCB.BaudRate = 9600
        udtDCB.Parity = NOPARITY
        udtDCB.ByteSize = 8
        udtDCB.StopBits = ONESTOPBIT
        lngReturn = SetCommState(lngHandle, udtDCB)
        If lngReturn <> 0 Then
            lngReturn = GetCommTimeouts(lngHandle, udtTimeOut)
            If lngReturn <> 0 Then
                '
                ' All timeouts zero
                '
                udtTimeOut.ReadIntervalTimeout = 0
                udtTimeOut.ReadTotalTimeoutConstant = 0
                udtTimeOut.ReadTotalTimeoutMultiplier = 0
                udtTimeOut.WriteTotalTimeoutConstant = 0
                udtTimeOut.WriteTotalTimeoutMultiplier = 0
                lngReturn = SetCommTimeouts(lngHandle, udtTimeOut)
                If lngReturn <> 0 Then
                    '
                    ' If everything went Ok enable the commands
                    ' to send and receive
                    '
                    cmdSend.Enabled = True
                    cmdReceive.Enabled = True
                Else
                    MsgBox "Unable to set Comm Port Timeouts " & Err.LastDllError
                End If
            Else
                MsgBox "Unable to Read Comm Port Timeouts " & Err.LastDllError
            End If
        Else
            MsgBox "Unable to set Comm Port Settings " & Err.LastDllError
        End If
    Else
        MsgBox "Unable to Read Comm Port Settings " & Err.LastDllError
    End If
Else
    MsgBox "Unable to Access CommPort " & Err.LastDllError
End If
End Sub

Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
Dim lngReturn As Long
lngReturn = CloseHandle(lngHandle)
End Sub

If you want to play with it, open a new project and on the form draw two CommandButtons (cmdSend & cmdReceive) set both their Enabled Properties to False.
Copy and paste the above into the Declarations Section of the Form and run the code. Hopefully both CommandButtons will appear enabled. Clicking on cmdSend should send the text to the Comm port and clicking on receive will receive from the comm port and display a MessageBox containing what was sent. Note that the program will 'hang' until something is sent from the serial port to the program after you click on cmdReceive.

[dhell]

Hello doogle,
wow,you're really expert in it. I tried your code and it worked. Although the application only receive the first character from the serial port, but that's a great help for me. I'll do the rest from here...
Thanks to cdrive and milk too...
Hope someday I will be someone who answer the threads hehehe

[Tommboy1337]

Hi, I'm wondering If i can open up this thread again. I tried your code Doogle, but I keep hanging when I start to press and the cmdSend button. I have no idea why its hanging or even trying to do at that function 'WriteFile' Can I have some help?

Also, I'm trying to close the port after it sends. It seems like I should use CloseHandler for this. Do you agree?

[aaronik19]

I am trying to use MSCOMM to recieve Date and Time from a device. The code is:

Private Sub MSComm1_OnComm()

  Dim dummy As String
   dummy = MSComm1.Input
   Text1.Text = Text1.Text + dummy 'Obviously put this where you want
   
 
    
End Sub

but I would like also to print the data and time on label. How I can make it? I made the following:

label1.caption = dummy

but only one character was being displayed.

[DataMiser]

Label1.caption=Text1.Text & Now()