Difference in error-states: PCAN-USB vs PCAN-USB FD

[Pawel_G]

Hi!

In my team we are performing some CAN tests using PCAN-USB and PCAN-USB FD. We have faced some differences in handling no connection to any other node. Attempting to send frame via PCAN-USB (white one) makes it become Bus Passive State

pcan-usb1.png (112.46 KiB) Viewed 13035 times

While PCAN-USB FD (black one) remains active:

pcan-usb2.png (126.57 KiB) Viewed 13035 times

We are wondering what is the reason of such difference and which approach of handling this scenario is the most common?

Best regards, Paweł Gmurczyk

[M.Heidemann]

Hello,

On a CAN-Bus there always need to be at least 2 nodes present, otherwise the messages sent cannot be acknowledged and will lead to error states.
The PCAN-USB FD does need a termination to operate correctly, most likely you have also removed the termination hence why the node stays active.
The hardware on PCAN-USB and PCAN-USB FD is different, where the PCAN-USB is a SJA-1000 hardware, the PCAN-USB FD used an FPGA. Furthermore do both devices use different Transceivers.

And what do you mean by "handling such a scenario"? Ideally, at least 2 nodes are on the bus, the error will always show up
if no other nodes are present when sending CAN-Frames.
If it is present on a bus with other nodes active it most likely is a physical issue:

-> Other nodes are in listenonly-mode (Do not acknoweldge frames, transmitting noce gets no acknowledgment)
-> Missing termination
-> Wrong bitrate
-> broken cables, etc.

For further information feel free to contact us again.

Best Regards

Marvin