Write (FUN)¶

FUNCTION Write : ERROR

This function writes a CAN or CAN FD message (see also CreateMessage and CreateFdMessage) via a CAN or CAN FD interface specified by hDriver. If Write returns ERROR.NO_ERROR the message was successfully handed over to the lower layers and will be automatically released after successful sending (Note: Do not call FreeMessage on such handles anymore!). If the message cannot be sent the function returns the error code ERROR.SENDING_ERROR and sending process must be repeated later. Otherwise the message handle has to be manually freed by application (see FreeMessage).

Messages can be sent with different priorities. Messages with the same priority are sent in chronological order. Messages with higher priority (means lower usiPriority) are always sent prior to those with lower priority. Priority 0 has a special meaning: messages with priority 0 are sent as soon as possible prior to all other messages waiting for transport. If a priority level not valid for the driver is used the message is not sent and function returns an error code. If the applied coblD is registered for reception and transmit messages are activated for receiving (see TransmitMask and TransmitValue of Receiver), a message which was sent successfully can be received via Read with a current timestamp (if timestamps are supported by driver). The function IsTransmitMessage returns TRUE on such messages.

Note

Following rules are important when using CL2.Write:

In case of CL2.Write returns ERROR.NO_ERROR the message was successfully handed over to the CL2 layer.

Do not use the message handle anymore! It will be automatically released.

To avoid using such handles it is helpful setting hMessage to CAA.gc_hINVALID directly after calling CL2.Write

In case of CL2.Write returns any error, the message still belongs to the application.

Do not forget to release the message!

Example

In this example a classic CAN driver will be opened and a classic CAN message (CANopen NMT reset message) will be sent.

VAR
    xInitialized : BOOL;
    hDriver : CAA.HANDLE;
    hMsg : CAA.HANDLE;
    pData : POINTER TO BYTE;
    eError : CL2.ERROR;
END_VAR

IF NOT xInitialized THEN
    hDriver := CL2.DriverOpenH(usiNetId := 0,
                            uiBaudrate := 1000,
                            xSupport29Bits := FALSE,
                            ctMessages := 100,
                            peError := ADR(eError)
    );

    IF hDriver <> CAA.gc_hINVALID THEN
        xInitialized := TRUE;
    ELSE
        RETURN;
    END_IF
END_IF

//Create message
hMsg := CL2.CreateMessage(hDriver := hDriver,
                        cobID := 16#0,
                        usiLength := 2,
                        xRTR := FALSE,
                        x29BitID := FALSE,
                        peError := ADR(eError)
);

IF hMsg <> CAA.gc_hINVALID THEN
    //Get message data pointer
    pData := CL2.GetMessageDataPointer2(hMessage := hMsg, peError := ADR(eError));
    IF pData <> CAA.gc_pNULL THEN
        //initialize message data
        pData[0] := 16#81;
        pData[1] := 16#0;
    END_IF

    //send message
    eError := CL2.Write(hDriver := hDriver,
                      hMessage := hMsg,
                      usiPriority := 1, //highest priority
                      xEnableSyncWindow := FALSE
    );

    IF eError <> CL2.ERROR.NO_ERROR THEN
        //sending was not successful ==> release the message
        CL2.FreeMessage(hMsg);
    END_IF
END_IF

Example

In this example a CAN FD driver will be opened. The program sends a CAN FD and a classic CAN messge over the CAN FD interface.

VAR
    xInitialized : BOOL;
    hDriver : CAA.HANDLE;
    hMsg : CAA.HANDLE;
    pData : POINTER TO BYTE;
    eError : CL2.ERROR;
    usiIndex : USINT;
END_VAR

IF NOT xInitialized THEN
    hDriver := CL2.FdDriverOpenH(usiNetId := 0,
                                uiNominalBaudrate := 500,
                                uiDataBaudrate := 4000,
                                xSupport29Bits := FALSE,
                                ctMessages := 100,
                                peError := ADR(eError)
    );

    IF hDriver <> CAA.gc_hINVALID THEN
        xInitialized := TRUE;
    ELSE
        RETURN;
    END_IF
END_IF

//Example 1: Send a CAN FD message
hMsg := CL2.CreateFdMessage(hFdDriver := hDriver,
                        cobID := 16#123,
                        usiLength := 64,
                        x29BitID := FALSE,
                        xBitrateSwitching := TRUE,
                        peError := ADR(eError)
);

IF hMsg <> CAA.gc_hINVALID THEN
    //Get message data pointer
    pData := CL2.GetMessageDataPointer2(hMessage := hMsg, peError := ADR(eError));
    IF pData <> CAA.gc_pNULL THEN
        //initialize message data
        FOR usiIndex := 0 TO 63 DO
            pData[usiIndex] := usiIndex;
        END_FOR
    END_IF

    //send message
    eError := CL2.Write(hDriver := hDriver,
                      hMessage := hMsg,
                      usiPriority := 1, //highest priority
                      xEnableSyncWindow := FALSE
    );

    IF eError <> CL2.ERROR.NO_ERROR THEN
      //sending was not successful ==> release the message
      CL2.FreeMessage(hMsg);
    END_IF
END_IF

//Example 2: Send a classic CAN message
hMsg := CL2.CreateMessage(hDriver := hDriver,
                        cobID := 16#0,
                        usiLength := 2,
                        xRTR := FALSE,
                        x29BitID := FALSE,
                        peError := ADR(eError)
);

IF hMsg <> CAA.gc_hINVALID THEN
    //Get message data pointer
    pData := CL2.GetMessageDataPointer2(hMessage := hMsg, peError := ADR(eError));
    IF pData <> CAA.gc_pNULL THEN
        //initialize message data
        pData[0] := 16#81;
        pData[1] := 16#0;
    END_IF

    //send message
    eError := CL2.Write(hDriver := hDriver,
                      hMessage := hMsg,
                      usiPriority := 1, //highest priority
                      xEnableSyncWindow := FALSE
    );

    IF eError <> CL2.ERROR.NO_ERROR THEN
        //sending was not successful ==> release the message
        CL2.FreeMessage(hMsg);
    END_IF
END_IF

InOut:

Scope	Name	Type	Comment
Return	`Write`	ERROR	error
Input	`hDriver`	`CAA.HANDLE`	handle of CAN or CAN FD interface
	`hMessage`	`CAA.HANDLE`	handle of classic CAN or CAN FD message to be written
	`usiPriority`	`USINT`	priority of message: 0: send immediately; 1-n: priority (1: high, n: low), default is n = 8
	`xEnableSyncWindow`	`BOOL`	use SYNC window => not implemented; do not care