MSComm Control Problem...Help! - Xtreme Visual Basic Talk

08-16-2006, 01:59 AM

aldinlapinig aldinlapinig is offline

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Join Date: Aug 2006

Posts: 4

MSComm Control Problem...Help!

Hi all,

I have a problem using MSComm Control for vb6... first I have to show u a little snippet of a program:

Assumption: Port settings already setup

Code:

Public Sub Command1_Click()
   MSComm1.Inputlen = 0
   MSComm1.RThreshold = 1
   MSComm1.Output = "AT" & vbCr
End Sub

Private Sub MSComm1_OnComm()
   Dim in_buffer as String
   
   Select Case MSComm1.CommEvent
        Case Is = comEvReceive            
            in_buffer = MSComm1.Input
        Case else
   End Select
End Sub

The problem is that, I could not read the entire content of MSComm1.Input (hardwarely, input buffer). As far as I know, it should read the entire content of the input buffer because I set the Inputlen property of the Comm Control to zero and that it would trigger the OnComm method if a character is received in the input buffer. The following is the result if the program is executed:

I sent: AT<cr> and I should receive: AT<cr><cr><lf>OK<cr><lf>

but I could only read:
in_buffer = "AT<cr>"

the remaining of the response packet is in the MSComm1.Input (I added watch to the control input property):
MSComm1.Input = "<cr><lf>OK<cr><lf>"

What could be the possible reason to this? Any idea on how I could solve this? I already researched about MSComm on the net and no information regarding this matter is available. Can anybody give me a good resource for understanding the inner working of MSComm Control? Thank you very much. I highly appreciate your time and help.

Kind Regards,
-=alDin=-

08-16-2006, 02:11 AM

DougT

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Posts: 3,939

Hi,

It's a matter of timing. The OnComm event is triggered when the first character is received (RThreshold = 1) at the time you issue the MSComm1.Input only "AT<cr>" has been received. By the time Watch reports the buffer has been cleared (because you read the "AT<cr>" ) and the rest of the data has arrived. If you let it run you will see that you actually receive more than one OnComm event so you have to concatinate the input until you have received all the message.

Regards
Doug

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08-16-2006, 02:26 AM

namrekka

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Join Date: Feb 2005

Location: Netherlands

Posts: 219

Also fill your own buffer with:

Code:

in_buffer =in_buffer & MSComm1.Input

08-16-2006, 03:28 AM

DougT

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Location: Maldon,Essex, UK

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Quote:

Originally Posted by namrekka

Also fill your own buffer with:

Code:

in_buffer =in_buffer & MSComm1.Input

Make sure that in_buffer is defined as Static in the OnComm Event or is defined in the Declarations section of the form.

__________________
semel insanivimus omnes
S Data in context = Information, S Information in context = Knowledge, S Knowledge in context = Experience
S Experience in context = Wisdom= Data