Serial Communication (API-calls) and possible error in CW API-Viewer 
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 Serial Communication (API-calls) and possible error in CW API-Viewer

Could anyone please help me out on the following:

API-calls for Serial-Communication.
-----------------------------------
I've obtained the prototypes for these calls via the API-viewer
which comes with CW20.
Additionally, I've obtained the necessary parameter datatypes/structures
and added these definition at the appropriate places in my application.

The problem.
------------
    [ I've used the following API-call to open communication to COM1/COM2:   ]
    [ CreateFileA(*LPCSTR,DWORD,DWORD,*SECURITY_ATTRIBUTES,DWORD,DWORD,HANDLE),HANDLE,Pascal,RAW ]
    [ This function returns a handle/filedescriptor; HCOM.                   ]
    [ The handlevalue returned by CreateFileA is greater than 0, but I'm not ]
    [ 100% sure that the operation succeeded.                                ]
    [ The function is called like this:                                      ]
    [ Hcom = CreateFileA(DeviceName,FileIOMask,0,Security,OPEN_EXISTING,0,_NULL_) ]

    After (hopefully) obtaining the filedescriptor/handle (HCOM), I use the
    following function to obtain the CURRENT settings for the
    communication-port:

                GetCommState(HANDLE,*DCB),BOOL,PASCAL

    According to the CW API-Viewer,     |   On the other hand, Microsoft
    the DCB-structure is supposed       |   claims (ref: MSDN-CD) DCB
    to be like this:                    |   consists of the following:
                                        |
    DCB        GROUP,TYPE               |   DCB        GROUP,TYPE
     Id           BYTE                  |   DCBlength         ULONG
     BaudRate     UNSIGNED              |   BaudRate          ULONG
     ByteSize     BYTE                  |   fBinary           ULONG
     Parity       BYTE                  |   fParity           ULONG
     StopBits     BYTE                  |   fOutxCtsFlow      ULONG
     RlsTimeout   UNSIGNED              |   fOutxDsrFlow      ULONG
     CtsTimeout   UNSIGNED              |   fDtrControl       ULONG
     DsrTimeout   UNSIGNED              |   fDsrSensitivity   ULONG
     XonChar      STRING(1)             |   fTXContinueOnXoff ULONG
     XoffChar     STRING(1)             |   fOutX             ULONG
     XonLim       UNSIGNED              |   fInX              ULONG
     XoffLim      UNSIGNED              |   fErrorChar        ULONG
     PeChar       STRING(1)             |   fNull             ULONG
     EofChar      STRING(1)             |   fRtsControl       ULONG
     EvtChar      STRING(1)             |   fAbortOnError     ULONG
     TxDelay      UNSIGNED              |   fDummy2           ULONG
    END                                 |   wReserved         SIGNED
                                        |   XonLim            SIGNED
                                        |   XoffLim           SIGNED
                                        |   ByteSize          BYTE
                                        |   Parity            BYTE
                                        |   StopBits          BYTE
This is confusing!                      |   XonChar           STRING(1)                                  |   XonChar           STRING(1)
Anyway - when used as parameter in the  |   XoffChar          STRING(1)                                  |   XoffChar          STRING(1)
GetCommState API-Call, *neither*        |   ErrorChar         STRING(1)                              |   ErrorChar         STRING(1)
of these structures' datamembers,       |   EofChar           STRING(1)                              |   EofChar           STRING(1)
e.g. DCB:BaudRate, result in correct    |   EvtChar           STRING(1)                              |   EvtChar           STRING(1)
values.                                 |   wReserved1        SIGNED                                 |   wReserved1        SIGNED
Furthermore, the testapplication        |   END                                                      |   END
performs an illegal operation
and shuts down.

I've narrowed down the possible errors to the following:
--------------------------------------------------------
    * The CreateFileA-function fails, eventhough it returns a value
      greater than 0, resulting in everything following it to fail too.
        - CreateFileA(*LPCSTR,DWORD,DWORD,*SECURITY_ATTRIBUTES,DWORD,DWORD,HANDLE)
          takes SECURITY_ATTRIBUTES as a pointer.
          The structure is defined like this and added to the testapplication:
              SECURITY_ATTRIBUTES     GROUP,TYPE
               nLength                  DWORD
               lpSecurityDescriptor     LPVOID
               bInheritHandle           BOOL
              END
          The structure variable is created like this:
              Security  LIKE(SECURITY_ATTRIBUTES)

          Does the compiler fix the pointer-parameter when perforiming:
          Hcom = CreateFileA(DeviceName,FileIOMask,0,Security,OPEN_EXISTING,0,_NULL_)
          ??
          If not, how should it be done??
    * Both DCB-structures suggested here are incorrect. (I've tried
      both)
    * The following declaration is incorrect for declaring a DCB-variable:
        DCBStruct   LIKE(DCB)
    * When calling GetComState, the following syntax is wrong:
      GetComState(HCOM, DCBStruct)
        - Should the DCBStruct variable be defined as a reference variable?
          (If yes; How?)
        - GetCommState(HANDLE,*DCB) indicates that DCB (=DCBStruct) is
          a pointer to a structure.  Does clarion resolve this automatically
          when compiling?  If not, how should it be done?

I urge someone from TOPSPEED to answer (too), since it seems like
the API-viewer has an incorrect DCB-structure definition...

    In advance, thanx.

        Regards,
            Eljar Ness



Thu, 19 Aug 1999 03:00:00 GMT  
 
 [ 1 post ] 

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