Transmitting Standard vs. Extended CAN frames using Visual Basic and the Gryphon DLL

The following code snippet works under the assumption that a Gryphon session has been activated¹, and that a channel handle has been obtained² for the desired CAN channel.


Dim tx_canframe(12) As Byte

Dim tx_gcframe As Long

tx_gcframe = dgCreateFrameHandle(FT_DATA)



' Fill the tx_canframe array with the desired CAN frame data.

' For example:

  tx_canframe(0) = &H01

  tx_canframe(1) = &H23

  tx_canframe(2) = &H45

  tx_canframe(3) = &H67

  tx_canframe(4) = &H89

  tx_canframe(5) = &Hab

  tx_canframe(6) = &Hcd

  tx_canframe(7) = &Hef




' To send the above example as a Standard CAN frame:



  dgSetHeaderLength(tx_gcframe, 2)

  dgSetHeaderBits(tx_gcframe, 11)

  dgSetDataLength(tx_gcframe, 6)



' Else, to send it as an Extended CAN frame:



  dgSetHeaderLength(tx_gcframe, 4)

  dgSetHeaderBits(tx_gcframe, 29)

  dgSetDataLength(tx_gcframe, 4)



' In both cases, follow with:



  dgSetPayload(tx_gcframe, tx_canframe(0))

  dgSendFrame(session, channel, tx_gcframe)

In summary: for Standard CAN the "HeaderLength" of the data frame is set to "2" and the "HeaderBits" is set to "11"; for Extended CAN, the "HeaderLength" is set to "4" and the "HeaderBits" is set to "29". The data frame is then used as a parameter in call to dgSendFrame(),

Note that in the above code snippets, function call return value checking is omitted in order to more clearly demonstrate the required logic. In a real program, however, it is strongly recommended that every return value be checked for error conditions, and acted upon accordingly.

Footnotes

1 See dgBeginSession(), Gryphon C Library User's Manual, Dearborn Group Inc.
2 See dgGetChannel(), Gryphon C Library User's Manual, Dearborn Group Inc.