Serial Port Timeout Detection

[kh1234567890]

How do you detect that a timeout had occurred using the in-built PB 4.32 serial port functions ?

There are no obvious clues in the documentation.

[Rook Zimbabwe]

You have to keep checking to see if it is active.

Interesting username?

[John Puccio]

Hi KH 1 thru 0,

Serial ports don't exactly time out, they are closed just like a file. Basically the host program says "if I do not see activity for X amount of time then close the port" that's how you get a timeout. What you need to do is look at the DCD line (Data Carrier Detect) if it is low then you have no carrier (no connection) and thus your timeout.

Hope that helps.

JP

[kh1234567890]

Thanks for the replies.

So when the serial port 'times out' after an interval set by SerialPortTimeouts it just closes and disappears ?

I was hoping for something more useful - I suppose it is back to the kludge of using the API timer to periodically check if any characters have appeared in the serial buffer.

In this application I have a simple three wire serial connection with no handshaking lines, connected to an unpredictable data acquisition front end sending data whenever it feels like it.

It is all coming back, why I gave up on PB about four years ago

kh1234567890 (because people kept using kh1, kh2 etc.)

[dhouston]

Create a separate thread for your serial port receive procedure.

Code: Select all

If IsSerialPort(ComID):ComThread=CreateThread(@ComEventRcv(),0):EndIf

Code: Select all

Procedure ComEventRcv(*nada)          ;serial input thread
  Protected ComRcv.s,char.s=" ",buffer.b,n
  Repeat
    If IsSerialPort(ComID)
      While AvailableSerialPortInput(ComID)   
        n=ReadSerialPortData(ComID,@buffer,1)
        Select buffer ;Asc(char)
          Case 10,13,32 To 126:ComRcv+Chr(buffer)
        EndSelect
        If Right(ComRcv,2)=#CRLF$
          If CmdMode
            cmd=Left(ComRcv,Len(ComRcv)-2)
          Else
            UpdateIO(Left(ComRcv,Len(ComRcv)-2))
          EndIf  
          ComRcv=""
        EndIf
      Wend 
    EndIf  
  ForEver
EndProcedure

[kh1234567890]

Neat !

Thanks, I'll try that.

[Edit]
Works fine, just needed a short delay in the Repeat loop to stop the thread hoarding the processor.
Thanks again.

kh

[John Puccio]

Thanks for the replies.

So when the serial port 'times out' after an interval set by SerialPortTimeouts it just closes and disappears ?

I was hoping for something more useful - I suppose it is back to the kludge of using the API timer to periodically check if any characters have appeared in the serial buffer.

In this application I have a simple three wire serial connection with no handshaking lines, connected to an unpredictable data acquisition front end sending data whenever it feels like it.

It is all coming back, why I gave up on PB about four years ago

kh1234567890 (because people kept using kh1, kh2 etc.)

EDIT:

KH

I'm glad you found a workable solution. Just to clarify, It's not a PB issue. It's a com port issue. Looking over my old docs, in a 3 wire no handshake situation there is no carier signal so DCD doesn't even apply.

JP