[RESOLVED] Comm port and API

I am developing an application to use the serial port using API calls. I have been able to transmit corectly and control de RTS signal at my desire (need it to implement a rs-323 to rs-485 convertion), but I have not ben able to receive any bytes. I have chekd the signal at the RX pin in the PC and it is OK. The hardware wotks fine with a previous app that used the VB6 comm object. Can anyone help me out? I beleive is something to do with the configuraion, here is what I am doing:

VB Code:

Dim D As DCB, cto As COMMTIMEOUTS
    Dim DCBString As String
    
    Dim lRet&
    Dim Status As Long
 
    SetupPort = False
    Erm = ""
 
    D.DCBlength = Len(D)
 
    If GetCommState(cmn.hFile, D) = 0 Then
        Erm = "Error Getting " + cmn.Port + " parameters"
        Exit Function
    End If
 
' ---
    'Parámetros del puerto
    'd.DCBlength = Len(d)
    D.BaudRate = CBR_9600                   'Velocidad
    D.fBinary = 1                           'Binary Transfers ALWAYS TRUE
    D.fParity = 1                           'Verificar paridad
    'D.fOutxCtsFlow = 1                      'Hardware Control, monitor CTS
    D.fOutxDsrFlow = 0                      'Hardware Control, controlar DSR
    D.fDtrControl = DTR_CONTROL_DISABLE     'Hardware Control, DTR flow control
    D.fDsrSensitivity = 0                   'Hardware Control, monitor DSR
    'D.fTXContinueOnXoff = 0                 'XOn/XOff Control, manejo del buffer
    'D.fOutX = 0                             'XOn/XOff Control, transmisión
    'D.fInX = 0                              'XOn/XOff Control, recepción
    'D.fErrorChar = 0                        'Replace Error Chars
    'D.fNull = 0                             'Discard Null bytes
    D.fRtsControl = RTS_CONTROL_DISABLE     'Hardware Control, control RTS
    'D.fAbortOnError = 0                     'Control de Errores
    'D.fDummy2 = 0                           'RESERVADO, no usar
    'D.wReserved = 0                         'RESERVADO, debe ser o
    'D.XonLim = 0                            'Bytes minimo para activar control de flujo
    'D.XoffLim = 0                           'Bytes máxim para activar control de flujo
    D.ByteSize = 8                          'Cantidad de bits
    D.Parity = NOPARITY                     'Paridad (solo si fParity)
    D.StopBits = ONESTOPBIT                 'Bits de parada
    'D.XonChar = 255                         'Caracter XOff
    'D.XoffChar = 254                        'Caracter XOn
    'D.ErrorChar = 0                        'Caracter de reemplazo en error
    'D.EofChar = 0                          'Caracter de fin
    'D.EvtChar = 0                           'Caracter de evento
    
    'Crear la estructura
    'DCBString = "COM1: baud=9600 parity=N data=8 stop=1" ' to=off xon=off odsr=off octs=off dtr=off rts=off idsr=off"
    'lRet = BuildCommDCB(DCBString, D)
    'If lRet = 0 Then
    '    'No se pudo crear la estructura
    '    Erm = "Error Setting Com State"
    '    Exit Function
    'End If
 
 
 
    If SetCommState(cmn.hFile, D) = 0 Then
        'Error al cambiar el estado del puerto
        Erm = "Error setting " + cmn.Port + " parameters"
        Debug.Print Err.Description
        Exit Function
    End If
 
 
    ' --- In Out Buffer sizes
    If SetupComm(cmn.hFile, 256, 256) = 0 Then
        'No se pudieron cnfigurar los buffers
        Erm = "Error on API SetupComm()"
        Exit Function
    End If
 
    ' Setup Timeouts in Milliseconds
    cto.ReadIntervalTimeout = 100 
    cto.ReadTotalTimeoutMultiplier = 100    
    cto.ReadTotalTimeoutConstant = 80      
    
    cto.WriteTotalTimeoutMultiplier = 100
    cto.WriteTotalTimeoutConstant = 10
 
    If SetCommTimeouts(cmn.hFile, cto) = 0 Then
        Erm = "Error setting " + cmn.Port + " timeouts"
        Exit Function
    End If
    
    Call PurgeComm(cmn.hFile, PURGE_RXCLEAR)
    Call PurgeComm(cmn.hFile, PURGE_TXCLEAR)
    Call PurgeComm(cmn.hFile, PURGE_RXABORT)
    Call PurgeComm(cmn.hFile, PURGE_TXABORT)
 
    If GetCommModemStatus(cmn.hFile, Status) = 0 Then
        Erm = "Failed GetCommModemStatus()"
        Exit Function
    End If
 
    ' --- Good Exit
    SetupPort = True

The following code is used to read data form the port

VB Code:

ContBytes = 0
    'Recibir solo por un tiempo
    PortTmr.StartTimer
    Do While PortTmr.ElapsedTime < TimeOut
        'Esperar a que lleguen datos al buffer
        res = SetCommMask(cmn.hFile, EV_TXEMPTY Or EV_RXCHAR)
        CommEvent = 0
        res = WaitCommEvent(cmn.hFile, CommEvent, Null)
        Do
            res = ReadFile(cmn.hFile, DataTemp, 1, BytesRead, OverRes)
            If res = 0 Then
                Debug.Print Err.Number
                Debug.Print Error(Err.Number)
                Debug.Print Err.LastDllError
                Debug.Print Error(Err.LastDllError)
            End If
        Loop While BytesRead > 0
        ContBytes = ContBytes + BytesRead
        Data = Data & DataTemp
        If ContBytes = NumBytes Then
            RxData = True
            Exit Do
        End If
    Loop

The waitcommevent function returns and the event tells me there was a byte received. But when I read de port I get an error. The erros's message is "Error defined by the application or object". So I can not tell what is failing.

Any ideas will be appreciated
thanks! :)

Re: Comm port and API

I've ben doing some tests. If I call the ReadFile with the bytes to read in 0, the function returns ok. If I put something bigger than 0, I will get the error. I then called the
VB Code:
resVal = ClearCommError(cmn.hFile, CommEvent, CommStatus)
which yields no error and tells me that there r 4 bytes that have not been read by the ReadFile function. I am getting out of options... :confused:

Re: Comm port and API

Ok, using the err.lastdllnumber i now know the error is 998 = Invalid access to memory location. Does this mean that I am opening the file/comm port wrong?

Re: Comm port and API

Solved it. The problem is with the interpretation of the ReadFile parameters:
VB Code:
Private Declare Function ReadFile Lib "kernel32" ( _
ByVal hFile As Long, lpBuffer As Any, _
ByVal nNumberOfBytesToRead As Long, lpNumberOfBytesWritten As Long, _
lpOverlapped As Any) As Long
Accordig to MSDN:

Quote:

lpBuffer
[out] A pointer to the buffer that receives the data read from a file.

So when calling ReadFile it returns in this parameter a pointer where the data is. I was doing
VB Code:
resVal = ReadFile(cmn.hFile, Byval Data, EventBytes, BytesWritten, CommOver)
Which returned the 998 error beacuse the variable Data's pointer can't be modified.

Work arround:

Pass a Dataptr as long and then copy the memory contents using CopyMemory

I hope that it helps any others!