CAN Communication without transceiver using s32k144 and another controller

[Shubha_Ravi]

Hello Team,

For my project, i currently have two CAN nodes, one with transceiver and other without transceiver. i have built a CAN driver level code using the Canpal_s32k144 example and my node with tranceiver communicates successfully.

The issue is with the CAN communication without CAN tranceiver, For this set up i referred to siemens_AP2921.pdf (mikrocontroller.net) and iam using the below setup in which node A is the S32k144 controller and Node B a different controller and using the same driver level code as above for reception and transmission, but iam not able to establish a successful communication between them, I am unable to decode the signal on the bus through picoscope as well as shown below. When i try to trace the CAN transmit message in the software, it results in CAN Transfer status as busy. Could you please provide some more information on this single wire CAN communication using NXPS32k144 controller. Please let me know if I am missing something?

[Julián_AragónM]

Hi @Shubha_Ravi

We do not have much documentation for CAN communication without a transceiver, as this is probably not viable in production for automotive grade. I can see form the SIEMENS documentation, the maximum wire length is limited (<<1m) and disturbances due to noise can occur. 

I'm not sure if your environment complies with these recommendations, and even if it did, this cannot be recommendable for any highspeed and critical communication. Is CAN protocol needed in this implementation? Maybe SPI can be used instead? 

Moreover, I cannot test this setup because the second node is a third-party controller. You could try to reduce noise, distance, etc. You could also test the communication by adding a third node (like a PCAN analyzer) as discussed in this community post: Solved: Question about CAN connection without transceiver - NXP Community.

Also, single-wire communication was discussed in another community post, please go over it as it may prove useful: Solved: One Wire Communication with S32k146 - NXP Community.

Best regards,
Julián