Sending & Receiving Via Com1

[Wesley Brown]

I am having trouble figuring out how to receive serial data via COM1. I have searched theforum but have yet to find
anything that will help me. For academic purposes I modified Comm.bas (PB/Dll sample program) so that a known string
of bytes would be sent whenever the "Send Text" button is pressed. (code from modified comm.bas follows)

>>>  CALLBACK FUNCTION Send_Callback() AS LONG
>>>
>>>  COMM Send #hComm, CHR$(02, 04, 05, 06, 17, 30, 39, 41, 46)
>>>
>>>  FUNCTION = %TRUE
>>>  END FUNCTION

I compiled this code and moved it over to a different machine sitting less than 2 feet away.The two machines are connected
together via a 9-pin null-modem cable (2-3, 3-2, 5-5). (The cable works fine when using HyperTerminal between the machines
at 9600)

The "receiving" machine is running the following:

>>>  ' Create A "Listen" Thread To Monitor Input From Console
>>>  Thread Create ReceiveData(hDlg) To hThread&
        .
        .
        .
>>>  Function ReceiveData(ByVal hWnd As Long) As Long
>>>  Dim DataIn As String
>>>  DataIn$ = ""
>>>
>>>  While IsFalse ThreadClose
>>>     If (Comm(#hComm, RxQue) < 9 ) Then
>>>           Sleep 1
>>>           Iterate Loop
>>>        End If
>>>
>>>     Comm Recv #hComm, 9, DataIn$
>>>     Control Set Text hDlg, %MesgBox, DataIn$
>>>  
>>>  Wend
>>>  Function = %TRUE
>>>  End Function

This set-up started out being much more complicated. But even after reducing it to what you see here, I still can't get it
to work. What I expected was for the ASCII values of "02, 04, 05, 06, 17, 30, 39, 41, 46" to show up in the "%MesgBox"
TextBox after pressing "Send Text" on the machine running Comm.bas . What I get, after pressing "Send Text" on theComm.bas
program 12 times (sometimes 11, sometimes 13), is "ÿÿÿÿÿÿÿÿÿ". On the surface it certainly looks like a baud rate is one
of the problems; among some of the things that I've tried is lowering the baud rate down to 300 (on both machines of
course). I have checked and re-checked the port settings and they are correct. About the only thing that is even slightly
encouraging is that there are 9 of the ÿ's showing up.

If it makes any difference, when the academics are over the "real" program will be sending and receiving binary data.

Thanks for taking the time to read this. Any help would be much appreciated.

Wesley Brown


------------------

[Lance Edmonds]

You say the settings are correct, but how have you actually configured the comm ports? Did you retain the COMM SET statements used in the original example, or have you omitted or changed them?

Without seeing the complete code you are using, it is a bit difficult to offer exact answers... would it be possible for you to post the code? Thanks!


------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Wesley Brown]

I solved the problem by further modifying Comm.bas so that it would transmit displayable characters rather than
control characters as follows . . .

>>> CallBack Function Send_Callback() As Long
>>> Comm Send #hComm, Chr$(&H41) 'A
>>> Comm Send #hComm, Chr$(&H42) 'B
>>> Comm Send #hComm, Chr$(&H43) 'C
>>> Comm Send #hComm, Chr$(&H44) 'D
>>> Comm Send #hComm, Chr$(&H45) 'E
>>> Comm Send #hComm, Chr$(&H46) 'F
>>> Comm Send #hComm, Chr$(&H47) 'G
>>> Comm Send #hComm, Chr$(&H48) 'H
>>> Comm Send #hComm, Chr$(&H49) 'I
>>> Comm Send #hComm, Chr$(&H4A) 'J
>>> Comm Send #hComm, Chr$(&H4B) 'K
>>> Comm Send #hComm, Chr$(&H4C) 'L
>>> Function = %True
>>> End Function

I'm still not clear as to why I wasn't at least getting trash on the first click of "Send Text' rather than the 12th
(or 11th or 13th); but I am willing to accept that it has something to do with the warning in the PowerBasic help
files concerning 'COMM SEND' which states:

"Be careful when using fixed length strings, as trailing padding in the string may give unexpected results in your
data flow. This is especially true is you are performing a binary file transfer through the serial port, the
padding bytes will produce a binary file at the “remote end” with interspersed spaces. Also, avoid using ASCIIZ
strings with binary data, as the first embedded zero byte will cause the data sent to the serial port to be
prematurely truncated, due to zero-byte termination of such strings".

Thanks for responding Lance. I apologize for posing a question to the forum after having worked for 17 hours
straight without first getting some sleep and pondering things longer.

Wesley Brown

------------------