Can I use USB Pro FD to send non-FD messages

[wfighter]

I have tried to use PCAN-USB Pro FD with a non-FD 250K CAN network. It received messages correctly but not able to transmit.

I used my other USB CAN adpater and checked. USB Pro FD received messages for USB CAN ok. But whenever I click to transmit a message message, it get error.

CAN_FD_Error.PNG (77.91 KiB) Viewed 9595 times

Any suggestions?

[K.Wagner]

Hello,

yes, you can use FD capable devices to send non-FD messages.

Please note that you may be using 250 kBit at different frequencies. The frequency selected on PCAN-View must be same as by the other participants.

[wfighter]

Hi K.Wagner,
Thanks for your kindly reply. I can not set the clockrate to 8Mhz for CAN Pro FD. While the standard PCAN adapter locked at this rate.

I noticed one behavior that seems incorrect: when I mixed CAN FD active and CAN FD inactive at channel 1 and channel 2. They communicate fine. My understanding is CAN FD can not transmit to normal CAN network and its package will set CAN error by CAN2.0 node.

CAN_FD_mixed_noError.PNG (98.74 KiB) Viewed 9585 times

It make me question whether that CAN FD active checkbox works the way I expect. If I unchecked CAN FD for PCAN-USB Pro FD device, will it work exactly same as a PCAN-USB device?

[K.Wagner]

Hello,

regarding the frequency, you need to select 24 MHz instead (this works since it is multiple of 8). Our new devices doesn't support 8 MHz, that's why.

CAN 2.0A/B can coexists with CAN-FD as long as the nominal bit rate used is the same for all participants, and no CAN FD messages are sent (no CAN-FD type set, no bit rate switch occurs).

The CAN FD checkbox with PCAN-View allows you to define (or not) a bit rate for the data phase. Note that the checkbox doesn't "causes" all messages to be send as CAN-FD frames. Each message has options than can be set separately (see attached picture).

In the attached picture you can see that one channel is initialized as normal CAN, the other as CAN-FD, and communication still work. If you mark a message as CAN-FD, then sending that message will end in an error, as you expected.

[wfighter]

Hi Wagner,
I did not know each messages can be set separately. That is good information. Thanks a lot.

Back to my original problem about the frequency, what is the right way to set up a PCAN FD pro to send messages to PCAN USB and other non FD nodes? I tried 24MHz, it had errors when I tried to send messages from FD Pro devices which set as Non FD.

CAN_FD_mixed_Error.PNG (849.55 KiB) Viewed 9568 times

[K.Wagner]

Hello,

If you have a normal PCAN-USB and a FD capable one (PCAN-USB Pro FD, for example), then the communication should work as explained, when you use for the FD Pro 24 MHz (see picture).

Please check that you have your connection well terminated: 120 Ohms termination resistor on both ends of your cable; and that there is not a third participant using a different bit rate configuration.