Question about CAN connection without transceiver

[snaku_lee]

Hi,

I have a question about the CAN transceiver application.

I connect CAN controllers between two MCU without transceiver, like below picture.

[ref to siemens_AP2921.pdf (mikrocontroller.net) ]

And I test CAN frames can transmit on each other correctly.

My question is that, I want to add a CAN transceiver on the 'wired CAN' bus, like below picture, let me transmit and receive CAN frames on the 'wired CAN' by a PCAN device for example. Is it possible to work?

I tried to use a PCAN with listen mode is OK, but normal mode is not work.

Regards,

Snaku

[kef2 · Accepted solution]

Without transceiver this ^^ is your bus. With transceiver bus is on other side of your transceiver, on CANH and CANL. So I think it should be like this:

Diodes may be not necessary if you can configure your CAN controller TxDC pins as open drain.

Edward 

[snaku_lee]

Hi Kef2,

Thanks for your reply, I think your solution will work when the 'wired bus' always connect to the CAN transceiver, am I right? but what I want is that the CAN transceiver is optional, these MCU can communicate with each other without the CAN transceiver.

Thank you,

Snaku

[kef2]

Either populate transceiver or put a short between transceivers RXD and TXD pads.

Edward

[snaku_lee]

Hi Kef2,

Got it, thanks for your support.

Snaku