Clear COM port buffer

[Jeff Barnes]

Hi,

Is there any other way to clear the com port buffer?
I have tried:

Code: Select all  Expand view

if FlushComm( nComm, 0 ) != 0
   nError = GetCommError( nComm )
   MsgInfo( "FlushComm Error: " + Str( nError ) )
endif

if FlushComm( nComm, 1 ) != 0
   nError = GetCommError( nComm )
   MsgInfo( "FlushComm Error: " + Str( nError ) )
endif
 

I do not get any errors but it appears that the buffer is not getting cleared.

What I am doing:
I read (every second) data form a com port and display the info on the screen.

What's happening:
At the start, the data being sent to the com port from my device will match what I see on the pc screen. After a few minutes, the data seen on the device and the pc screen are out of sync. If I change the info being sent on the device it can take up to 30 seconds before the pc screen catches up.

[Antonio Linares]

Jeff,

FWH provides CloseComm( nPort ), not sure if you may need to close it and open it again.

Anyhow if you post an example of how you are using it we will be able to provide you a better help,

[Jeff Barnes]

Here is a sample of the code.
lSetOX is set to .T. during the initial connection, then set to .F. after the connection is made.

The code below is called every second via a timer.

Code: Select all  Expand view

IF lSetOX    //Connect to device
   nComm:= OpenComm("COM"+ALLTRIM(STR(nComPort)), 16,16 )
   Syswait(.01)
   BuildCommDcb( "COM"+alltrim(str(nComPort))+":9600,N,8,1", @cDcb )

   IF ! SetCommState(  nComm, cDcb )
      MsgInfo("Error setting COM state","ERROR")
      RETURN .f.
   ENDIF

   IF !ENABLECOMMNOTIFICATION( nComm, oDlgTest:hWnd, 1, -1 )
      MsgInfo("COM Noticication error","NOTICE")
      RETURN .f.
   ENDIF

   IF FlushComm( nComm, 1 ) != 0
      nError = GetCommError( nComm )
      MsgInfo( "Error flushing the COM port: " + Str( nError ) )
   ENDIF   
   lSetOX:=.F.
ENDIF


//Read from device
Memory(-1)
FlushComm( nComm, 1 )
FlushComm( nComm, 0 )
SysRefresh()
cDataRead:=Space(18)
cString := ""
READCOMM( nComm, @cDataRead)
cString:=ALLTRIM(cDataRead)
cSat := LEFT( RIGHT(ALLTRIM(cString),12),3)
cHR  := LEFT( Right(ALLTRIM(cString), 5),3)
SysRefresh()
       
 

[Enrico Maria Giordano]

Jeff,

this is a sample of how should you use the communication device:

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#include "Fivewin.ch"


FUNCTION MAIN()

    LOCAL oDlg

    LOCAL oGet, cTxt := ""

    LOCAL nCom

    DEFINE DIALOG oDlg;
           SIZE 500, 500;
           TITLE "Terminale"

    @ 0, 0 GET oGet VAR cTxt MEMO READONLY

    oGet:bKeyDown = { | nKey | Tasti( nCom, nKey ) }

    ACTIVATE DIALOG oDlg;
             ON INIT ( oGet:AdjClient(),;
                       nCom := APRICOM( oDlg, oGet ),;
                       IF( nCom < 0, oDlg:End(), ) );
             CENTER

    IF nCom >= 0; CLOSECOMM( nCom ); ENDIF

    RETURN NIL


STATIC FUNCTION TASTI( nCom, nKey )

    SENDSTR( nCom, CHR( nKey ) )

    RETURN NIL


STATIC FUNCTION APRICOM( oDlg, oGet )

    LOCAL nCom, cDcb

    BEGIN SEQUENCE
        nCom = OPENCOMM( "COM1", 16384, 16384 )

        IF nCom < 0
            ? "Errore di apertura della porta di comunicazione."
            BREAK
        ENDIF

        BUILDCOMMDCB( "COM1:115200,N,8,1", @cDcb )

        IF !SETCOMMSTATE( nCom, cDcb )
            ? "Errore di impostazione della porta di comunicazione."
            BREAK
        ENDIF

        oDlg:bCommNotify = { | nCom | Connect( nCom, oGet ),;
                                      EnableCommNotification( nCom, oDlg:hWnd, 1, -1 ) }

        IF !ENABLECOMMNOTIFICATION( nCom, oDlg:hWnd, 1, -1 )
            ? "Errore di abilitazione della notifica."
            BREAK
        ENDIF
    RECOVER
        nCom = -1
    END SEQUENCE

    RETURN nCom


STATIC FUNCTION CONNECT( nCom, oGet )

    LOCAL cStr

    ENABLECOMMNOTIFICATION( nCom, 0, 1, -1 )

    cStr = RECEIVESTR( nCom )

    cStr = STRTRAN( cStr, CHR( 13 ), "" )
    cStr = STRTRAN( cStr, CHR( 10 ), CRLF )

    oGet:Append( cStr )

    RETURN NIL


STATIC FUNCTION SENDSTR( nCom, cString )

    LOCAL nBytes := WRITECOMM( nCom, cString )

    RETURN nBytes = LEN( cString )


STATIC FUNCTION RECEIVESTR( nCom )

    LOCAL cBuf := SPACE( 1000 )

    RETURN LEFT( cBuf, READCOMM( nCom, @cBuf ) )

EMG

[Jeff Barnes]

Hi Enrico,

I have been playing with your sample and it works perfectly to show the data coming in via your dialog box and get.
The problem I am having is using your example to put the data into a string instead of a get (without the "terminal" dialog box).

When I try without your dialog box and just placing the data into the string (Then I manipulate the string and show the extracted data in 2 gets) I do get the data but every 30 seconds the data appears to shift then goes back to normal.

Ex
cString = the entire data string read at the com port.
When I display cString, the initial reading will show "SPO2=999 HR=999"
After 30 seconds, cString will show as follows every second:
"O2=999 HR=999"
"=999 HR=999"
"99 HR=999"
" HR=999"
"R=999"
"999"
"9"
Then goes back to "SPO2=999 HR=999" for another 30 seconds then repeats.

Do you have an example where I can just collect the data and put into cString ?

[Enrico Maria Giordano]

Jeff,

this is how to read a string from the communication port:

Code: Select all  Expand view

cStr = RECEIVESTR( nCom )

It should work fine. I don't understand your problem, sorry...

Can I see a sample of the code you are using?

EMG

[fafi]

Jeff,

this is how to read a string from the communication port:

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cStr = RECEIVESTR( nCom )

It should work fine. I don't understand your problem, sorry...

Can I see a sample of the code you are using?

EMG

add this :

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cStr = RECEIVESTR( nCom )
cStr := upper(alltrim(cStr))
?"Len of string : "+str(len(cStr),12)
if cStr $ "1234567890=QWERTYUIOPASDFGHJKLZXCVBNM"
  ?"this is good string : "+cStr
else
   ?"garbage string : "+cStr
endif

or save the cStr every time to dbf

 

best regards
fafi

[Jeff Barnes]

Got it working ... I had to adjust the buffer size.
Thanks everyone for the help.

[PeterHarmes]

HI,

I have just created a link to a badge reader and have noticed that when I use EnableCommNotification, it only reads in around 8 characters at a time - This is happening in Enricos demo application. Is there a way to read in more characters in one go (10-20)?

Best regards,

Pete

[Enrico Maria Giordano]

Peter,

you should not care of how many characters are read at a time. Just read and store any characters you receive.

EMG