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Visual Basic Form | 1992-02-03 | 28.6 KB | 641 lines

Form_CommDemo Communications Demo Form1 Timer_CheckInBuf Timer_ClearStatusWin Label_ReceiveWin Recieve Window Text_ReceiveWin Label_TransmitWin Transmit Window Text_TransmitWin Label_StatusWinLab Communications Status Label_StatusWin MNU_File &File MNU_File_Exit E&xit MNU_Connect &Connect! MNU_BaudMenu &Baud MNU_BaudRate &1200 MNU_BaudRate &4800 MNU_BaudRate &9600 MNU_Events E&vents MNU_Events_CharDetect &Character Detect Form_Click Form_LinkClose Form_LinkErrorw LinkErr Form_LinkExecute CmdStr` Cancel Form_LinkOpenl @ Form_Load Screen Width4 Height4 OpenErrCode/ OpenCommPort InBufSize OutBufSize ComDev; MsgBoxCaption DefMsgCaptionn BaseComm carriage linefeed OpenCommErr Form_Unload OpenCommError DefaultLineSettings DefaultEventSettings} BaudRateT ByteSizeC Parity NOPARITY StopBits ONESTOPBIT RlsTimeOut` CtsTimeOut DsrTimeOuts ModeControl XonChar XoffChar XonLim XoffLimP peChar) EofChar EvtChar Label_StatusBar Caption SetCommState SetLineSettings valuea enablesV containedr received fOutX fDCBw OpenComm7 SetEventSettings DCBType MNU_File_Exit_Click+ CloseCommZ Timer_CheckInBuf_Timer ReadCommJ InBuf NumCharsRead Text_OutWin? SelStart SelTextZ InBuff SelLength number handshaking anything~ buffer displayg windowF Text_OutWin_Change[ Text_OutWin_GotFocus Text_InWinL Timer_CheckInBuf Enabled TrueI ReadCommInterval) Interval ErrFlag Text_InWin_Change= Text_InWin_KeyPresss KeyAsciiO CharsWritten WriteComm OutBuff4 entered Text_ReceiveWin_Change Text_TransmitWin_Change Text_TransmitWin Text_ReceiveWin{ Text_TransmitWin_KeyDown KeyCode Shift Text_TransmitWin_KeyPressE EventAddr SetCommEventMask EV_ALL Timer_ClearStatusBar_Timer! Label2_Click ShowStatus7 StatusText Timer_ClearStatusBar ClearStatusIntervall False. comst status DelayFlage delay DelayTime+ callingU Windows IE_OPEN Response ShowCriticalMessage/ ShowCritErrMessage ShowCritErr Label_ReceiveWin_Click ErrTypev ErrCode @ ShowErrorJ ExitRoutine CloseComFlag: ProcessCommError} CommErr GetCommErrorf COMSTATr CE_BREAK CommStat Message ShowMessage CE_CTSTO CE_STSTO= CE_DNS CE_FRAME CE_IOE CE_MODE8 CE_OOPX CE_OVERRUN CE_PTO' CE_RLSDTOu CE_RXOVERL CE_RXPARITY CE_TXFULL COMSTATType CommConnectB comments` herej CommID ComID GetCommStateJ DCB_Type MNU_Connect_Click ConnectFlag MNU_Connect CommDisconnect ConnectErrorr ConnectErrFlag IE_BADID IE_BAUDRATE. IE_BYTESIZE IE_DEFAULT IE_HARDWARE IE_MEMORYV IE_NOPEN Text_ReceiveWin_GotFocus CommConnectFlag COMSTAT_Type5 ShowErrorMessage ErrorFlag& Label_TransmitWin_Click ProcessCommEvents) EventMaskD GetCommEventMaskL CurrentEventMaskU EV_BREAK ShowStateV EV_CTR EV_CTS` EV_DSRj EV_ERR EV_PERR EV_RING; EV_RLSD EV_RXCHAR EV_RXFLAG EV_FXFLAG EV_TXEMPTY^ DisconnectComm? Form_CommDemo Form_Resize Text_. TxDelay cbInQue cbOutQuet lpCommName wInQueue wOutQueuej lpBuf nSize nEvtMask CE_DSRTO ODDPARITY EVENPARITY ONE5STOPBITS TWOSTOPBITS Label_StatusWin alreadyp opened alread ComDisconnect MNU_File_Click events detectz Label_StatusWin_ClickU Label_StatusWinLab_Click Disconnect ProcessComError Visual Basic Timer_ClearStatusWine Timer_ClearStatusWin_Timer GetOpenCommError FlushCommH BuildCommDCB6 MNU_BaudRate_Click Index BaudRate_Click LastIndex MNU_BaudRateT Checked PortID MNU_Baud_Menu MNU_BaudMenu MNU_BaudMenu_Click closed ComStatusCode GlobalDCB| CharsWaiting' MNU_Events_CharDetect_Click CurrEventMask MNU_Events_Click MNU_Events_CharDetectg CharDectEnabled CharDetectEnabled CharDetectEnabledFlag MNU_Eventsx Name of default communications device to be opened COM input and output buffer sizess Time interval to read the COM port (in milliseconds) The maximum period of time (in milliseconds) for which a status bar message will be displayed The time that message processing will be delayed (in seconds) while displaying a status bar message Device Control Block (DCB) for the COM port. Contains all of the current line settings for the COM port.T ID number representing the COM port. Set by calling the Windows API function SetCommState. Flag indicating successful COM connection. The current COM event settings. Set by calling the Windows API function SetCommEventMask Form_Load * This is the entry point of the program. Initialize global variables and center the form * on the screen. The Windows API function BuildCommDCB is called to assign default values too * the DCB (Device Control Block) data structure. Initialize global variables representing carriager return and carriage return linefeedn Center the form on the screen Disable the Events menu. The Events menu is enabled when the COM is connected Initialize the COM DCB (Device Control Block) with default line settings COM1:1200,N,8,1" Form_Unload Disconnect the COM only if the COM was connected from this programh SetLineSettings * Set default line settings (e.g. baud rate, parity, * data bits, stop bits and handshaking) by calling * the Windows API function SetCommState. * Note: The Chr$ function is used below to convert a numeric value to a 1 byte character value. This is needed because a byte is not supported as a numerical type under Visual Basic. The Asc function can be used to get the value of a 1 byte character representing a 1 byte numerical value. Setting line settings ..." Set the Id for the COM port. The COM port ID is returned by the Windows API function OpenComm Set line settings for the COM port as 1200:N,8,1,CD0,CS0,DS0,RS,TB2048,RB2048t The following parameter settings represent the default settings set by calling BuildCommDCB in the Form_Load event procedure. Set parameters as 1200: N,8,1M DCB.BaudRate = 1200 'Other possible values include 300, 2400, 4800, 9600, 19200. DCB.ByteSize = Chr$(8) 'Other possible values include 4,5,6,7 DCB.Parity = Chr$(NOPARITY) 'Other possible values include EVENPARITY, MARKPARITY, ODDPARITY, SPACEPARITY DCB.StopBits = Chr$(ONESTOPBIT) 'Other possible values include ONE5STOPBITS, TWOSTOPBITS Set timeout period for CD, CS and DS handshake lines respectively. Values represent milliseconds. A value of zero represents an infinite wait effectively disabling handshaking on that line. Possible values can range from 0 to 65,535s for an unsiged integer or -32,768 to 32,767 for signed integers. Carrier detect or receive-line-signal-detect (CD or RLSD) line (CD0) Clear-to-send (CTS) line (CS0) Data-set-ready (DSR) line (DS0)) The following bit flags are combined in the ModeControl field below. Becausec the following are bit fields they cannot be represented as a field of a Type ... End Type structurew DCB.fBinary = 1 Specify binary mode. Setting this to zero causes an EOF character (Chr$(26)) to signal the end of data. DCB.fRtsDisabled = 1 Disable request-to-send line (RS). A zero value enables the request-to-send linev DCB.fParity = 0 Disable parity checking. A value of 1 enables parity checking DCB.fOutCtsFlow = 0 Disable checking of clear-to-send line for output flow control DCB.fOutxDsrFlow = 0 Disable checking of data-set-ready (DSR) line for output flow control DCB.fDummy = 0 + 0 Two bit reserved fieldd DCB.fDtrDisabled = 1 Disable the data-set-ready line (DTR). A value of 1 enables DTR. DCB.fOutX = 0 Disable XON/XOFF during transmission.e A value of 1 enables XON/XOFF.d DCB.fInX = 0 Disable XON/XOFF during reception.i A value of 1 enables XON/XOFF DCB.fPeChar = 0 Disable the replace of parity error characters with the character contained in the PeChar field. A value of 1 enables replacementt of parity error characters with the character contained in then PeChar field. DCB.fNull = 0 Received null characters are not to be discarded. A value of 1c specifies that null characters received will be discarded.d DCB.fChEvt = 0 Reception of the character contained in the EvtChar field doesc not signify an event. A value of 1 indicates that thet reception of a character identical to the character contained in the EvtChar field signifies and event. DCB.fDtrFlow = 0 The DTR line is not used for receive flow control. A value of 1 indicates that the DTR line is used for receive flow control. DCB.fRtsFlow = 0 The RTS line is not used for receive flow control. A value of 1 indicates that the DTR line is used for receive flow control. DCB.fDummy = 0 Reserved 1100 0001 Binary representationr of the above bit settings Hex representation of the aboveu bit settings Based on the bit settings above XON character to be used. Only used if the fOutX or fInX fields are set to 1. XOFF character to be used. Used only if the fOutX or fInX fields are set to 1. Specifies minimum number of characters allowed in the receive buffer before the XON character is sent. Used only if the fOutX or fInX fields are set to 1. Specifies the maximum number of characters allowed in the receive buffer before the XOFF character is sent. Used only if the fOutX or fInX fields are set to 1.i Character used to replace characters received with a parity error. Used only if the fPeChar flag has been set to 1. Specifies the character used to indicate end of data. Used only if the the fBinary flag is set to 0.t Character indicating an event. Used only if the fChEvt flag is set to 1. MNU_File_Exit_Click * When the user selects Exit from the File menu, unload thee * form, disconnect the COM - if it is already opened - and * end the programm Timer_CheckInBuf_Timer * The code below represents a method of reading the COM port * by calling the Windows API function ReadComm.. * Check the input buffer on each timer interval by calling * the Windows API function ReadComm. If anything is found * in the buffer, display it in the receive window. COM status variable used by the Windows API function GetCommErrorb Allocate a buffer (a text string of spaces) the size of the specified input buffer.f Because the ReadComm API function expects to read to an existing buffer, failing to initialize the buffer may result in unpredictable results or a Windows UAE. Unlock the COM port if it had been locked as the result of a previous COM error. The number of characters waiting in the receive buffer will be returned as part of the COMSTAT structure Check to see if there are any characters waiting in the receive buffer Call the Windows API function to read information from the input buffer. Read all characters waiting in the input buffer.m Check for COM error by calling the Windows API function GetCommError If a COM error occurs, a message will be displayed and the COM port disconnected.f Check for COM events by calling the Windows API function GetCommEventMask. COM events, such as a ring detect, are displayed in the status window as they occur. Check to see if any characters were read from the input buffer Display the text read from the input buffer in the receive window SetEventSettings * Specify which events are allowed to occur by calling the Windows API function * SetCommEventMask.. Setting event settings ... Place a check mark next to the Events menu item Character Detect indicating that char detect has been enabled The following communication events are to be processed Event (constant) Descriptions EV_BREAK Set when a break is detected on input- EV_ERR Set when a line-status (CE_FRAME, CE_OVERRUN, CE_RXPARITY) error occurso EV_RING Set when a ring indicator is detected EV_RXCHAR Set when a character is received and placed in the COM receive buffer EV_TXEMPTY Set when the last character in the COM transmit buffer is sent Other possible values include: EV_CTS Set when the clear-to-send (CTS) signal changes stateu EV_DSR Set when the data-set-ready (DTR) signal changes state EV_PERR Set when a printer error is detected on a parallel device EV_RLSD Set when the receive-line-signal-detect (RLSD) signal changes state EV_RXFLAG Set when the event character is received and placed in the receive buffer Combine the events to be processed into the event mask. The bitwise Or operator is used toi combine the bit patterns of the constants representing the COM events. All possible communciations events may occur Text_TransmitWin_KeyPress * Writes the character for each key press to the output* * buffer by calling the Windows API function WriteComm Convert the ASCII code of the key pressed to an ASCII characterr Write the character to the COM output buffer by callingl the Windows API function WriteComm.u Check for COM error by calling the Windows API function GetCommError If a COM error occurs, a message will be displayed and the COM port disconnected.r Check for COM events. COM events, such as a ring detect, are, displayed in the status window as they occur.r ShowStatus * Display a caption within the status window at the bottom * of the main display window Show a message in the status window Delay (allow for the message to be read by the user) for a specified period of time Get the current clock count Loop for the amount of time specified by DelayTime (in seconds) without processing other Windows events Enable a timer to cause the status window to be clear after a specified period of time ShowError * Display standard error messages based on the type of error that occurred.. * The messages are displayed in a modal message box (MsgBox). Show message box indicating that an error occurred attempting to open the COM port Error occurred attempting to open Connection not established Error attempting to set line settings" Connection not established ProcessCommError * Determines if an error occurred after a COM operation. * * If an error occurred, a message is displayed indicating that the COM will be * disconnected. It is the responsibility of the calling routine to disconnect * the COM. * When an error occurs, Windows locks the COM port. Calling the * Windows API function GetCommError causes the COM port to be unlocked. COM status variable used by the Windows API function GetCommErrorE Find out if an error occured. Calling GetCommError clears the error and causes Windows to unlock the COM port. One or more of the following errors may have occurred Break condition detected Clear-to-send (CTS) timeout" Data-set-ready (DSR) timeout Parallel device is not selected" Framing error detected Device I/O error occurred" attempting to communicate with parallel device Requested mode is not supported" Out of paper on parallel device" Overrun error detected Timeout attempting to communicate with parallel device" Receive-line-signal-detect (RLS) timeout Receive buffer overflow" Parity error detected" Transmit buffer full CommConnect * Connect to the communications port by calling the following Windows API functions: OpenComm GetCommState SetCommState SetCommEventMask * The return values of OpenComm and SetCommState are tested for an error. If an * error occurs a message is displayed and the COM remains disconnected.r Assume that no error will occur opening COMr Opening COM port ... Attempt to open the COM port specifying the input and output buffer sizes Check to see if the COM port was successfully opened If the COM was successfully opened the return value of OpenComm represents the COM ID. Set communications line settings such as baud rate,d parity, data bits, stop bits and hardware handshaking. Select the allowable communication events by calling the Windows API function SetCommEventMask Display a message box indicating a critical error and end the programg Enable the timer to begin reading the COM input buffer.t Get the COM ID used in the call to BuildCommDCBa COM device already opened" Do you wish to use it anyway Close the com port if the user selected Yes from the message box The user chose not to use the COM port that is already opened. Show a critical error and terminate the programa A critical error occurred when attempting to open the COM port.p Attempt to open the COM port again if the COM port is already open, but the user wants to use it anyway Return False if an error occurred attempting to connectn Return True if connection was successful MNU_Connect_Click * When the user selects Connect! from the menu, connect to the COM port if itt * is not already opened by calling CommConnect. * When the user selects Disconnect! from the menu, disconnect from the COM * port if it is already opened by calling ComDisconnect. See if the COM is already a connected Disconnect the COM port by calling the Windows API function CloseComms Connect to the COM port by calling the following Windows API functions:u OpenComm SetCommStateM SetCommEventMaskS Make sure there was no error in connecting to the COM port.C If an error occurred, no attempt will be made to connect the COM port. &Disconnect! Enable the transmit and receive windowss CommDisconnect * Disconnect from the COM port by calling the Windows API function CloseComm * Disable the transmit and receive windows and reset the menu caption. Closing COM port ... Flush the transmit buffer Flush the receive buffer Call the Windows API function to close the COM port. The return value represents whether the comm was successfully closed or not, it is not used.n Invalid the COM ID to indicate that the COM was closed Turn off timer used to check COM receive bufferu Disable the transmit and receive windows Change the menu caption and connection status flag &Connect!" Disable the events menua Text_ReceiveWin_GotFocus * Do not allow the focus to be set to the receive window.* * If the user attempts to select the receive window, * restore focus to the transmit window.c ProcessCommEvents * Check to see if a communications event occurred by calling the Windows * API function GetCommEventMask. The event, such as a ring, is reported * in the status window.v Call Windows API function to get the COM event mask. The event mask iss a pattern of bits which represents one or more of the events below.n Check for the following events. The events that are reported are dependent on the event mask that was passed to SetCommEventMaskt Break detected on input" Clear-to-send (CTS) line changed state Data-set-ready (DTR) line changed state" Line status (framing, overrun or parity) error occurred" Printer error occurred Ring detected" Receive-line-signal-detect (RLSD) or carrier-detect (CD) line changed status Character received Event character received Last character sent: transmit buffer empty Timer_ClearStatusWin_Timer * After a status message has been displayed * for a certain interval, clear the status window- GetOpenCommError * FUNCTION: GetOpenCommError * PURPOSE: Returns an error message based on the specified error code. The error code is interrupted as related to an error when opening the COM device. This function handles all possible return codes. from the Windows API function OpenComm.r * PARMS: OpenErrCode - Specifies the error code relatede to the opening the COM porti * RETURNS: A string containing the error message associated with the error coden Invalid or unsupported ID" Unsupported baud rate" Invalid byte size" Error in default parameters" Hardware not present Unable to allocate queues" Device not open" Device already opened" MNU_BaudRate_Click * Change the COM line settings to reflect the new baud rate selected by the user.. * Note that the baud rate (as with any line setting) can be changed if the portt * is open or closed. If the baud rate of the device being communicated with doess * not change, this could lead to unexpected behavior.. Get the baud rate selected Set the baud rate Modify the COM line settings with the new baud rate Put a check mark next to the baud rate selectedr Take the check mark away from the last baud rate selectedl MNU_Events_CharDetect_Click * Set or disable the ability to detect characters received * from the COM. * When enabled, character related events are displyed in * the status window when a character is received Get the status of the menu selection Toggle the check mark next to the menu itemv Disable character detect events by setting the EV_RXCHAR bit to 0e Enable character detect events by setting the EV_RXCHAR bit to 1 Set the COM event settings by calling a Windows API function