Changing bus speeds using Visual Basic and the Gryphon DLL

Changing bus speed using Visual Basic and the Gryphon DLL

This example assumes the use of a single wire CAN channel, and illustrates how to change the channel's transceiver to GMLAN SWC Low Speed and High Speed modes. The method used here is the modification of the channel's Bus Timing Register values via the Gryphon Protocol IOCtl mechanism.

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


Dim ioctl_num As Long

Dim ioctl_data(2) As Byte



dgGetSetSpeedIOCtl(hChannel, ioctl_num)



' GMLAN SWC High Speed BTRs: 0x47 0x98

ioctl_data(0) = &H47

ioctl_data(1) = &H98



dgIOCtl(hChannel, ioctl_num, ioctl_data(0), 2)

dgInit(hChannel, 0)



MsgBox ("channel is now in

GMLAN SWC

High Speed mode")



' GMLAN SWC Low Speed BTRs: 0x4f 0xaa

ioctl_data(0) = &H4F

ioctl_data(1) = &HAA



dgIOCtl(hChannel, ioctl_num, ioctl_data(0), 2)

dgInit(hChannel, 0)



MsgBox ("channel is now in

GMLAN SWC

Low Speed mode")

Note that in the above code snippet, 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.