CAN object data length always 8

[jjohannsen]

Maybe I'm missing something.  Using a NI-CAN PXI-8461/2 2-port HS CAN card, I configure a CAN object to 'receive unsolicited' CAN frames for a specific message ID.  In the config cluster, I set the Data Length to 5 bytes.  However, when starting and running the application, I always receive 8 CAN frames from the ncReadObjMult vi function.

Any ideas?

Thanks

Jason

[Sammy Z]

Hi Jason,

Would you please try wiring a constant with number 5 to RequestedDataBufSize terminal of the ncReadObjMult vi?

Regards,

Sammy Z.

[jjohannsen]

Yes, but then I will only receive 5 CAN frames; RequestedDataBuSize determines the # of frames to attempt to read.  They still have 8 bytes of data in each frame.

Jason

[Mr.F]

Hi,

The received frames have 8 bytes because that is how much information the CAN device transmitted.   Why do you not want to receive the last 3 bytes?

[jjohannsen]

When I use the CAN 'Bus Monitor' in MAX, I only receive 5 bytes of data, with the DLC of 5.  The device I am connected to transmits 5 data bytes.  But when using the ncCAN object, I always receive 8 data bytes from the VI call.

Jason