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I am working with CAN bus and have a microprocessor with builtin CAN controller (mpc5606B by NXP). I then came to know that I need a seperate transceiver for each CAN controller to establish communication. My question is 1.How a CAN controller and transceiver communicate with each other? 2. Is it possible to establish communication without a transceiver? Thank you

Sundar Santhanam
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  • Take a look at this, I don't know jack about CAN bus, but I expected some funky voltage levels something along TTL/CMOS etc. https://en.wikipedia.org/wiki/CAN_bus#Physical it says for instance high speed can CANH 3.5V CANL 1.5V – Sorenp Jan 08 '21 at 07:21
  • Btw if you don't even know how a CAN controller works and signed up for a MPC56 project, you kind of jumped in at the deep end of the pool before learning to swim. These MCUs are far from beginner-friendly and FlexCAN controllers are rather complex. – Lundin Jan 08 '21 at 09:08
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    Maybe this question helps https://electronics.stackexchange.com/questions/30564/is-a-can-enabled-microcontroller-sufficient-to-drive-a-can-bus?rq=1 – EarthLord Jan 08 '21 at 09:12
  • Thank you so much everyone – Sundar Santhanam Jan 08 '21 at 16:03
  • @EarthLord thank u so much for link – Sundar Santhanam Jan 08 '21 at 16:09

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  1. CAN controller talks with CAN PHY with TX and RX pins. Look up any CAN PHY tranceiver datasheet.

  2. Unless the MCU has a built-in CAN PHY, no it is not possible to connect to a CAN bus without a CAN PHY.

Justme
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  1. CAN transceivers are "dumb", you don't really commuicate with them but rather through them. The task of the CAN transceiver is to translate the Tx and Rx signals from the controller (logic voltage levels) into a differential signal consisting of CANHI and CANLO with +/- 2.5V levels.

    In this case, MPC56 are 3V3 so you will need a 3V3 tolerant transceiver. I would recommend to pick a modern one like MCP2562/MCP2562FD.

  2. No.

Lundin
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  • What kind of data comes out of the Rx and Tx pins of the CAN controller ? Is it the CAN message frames? After which it enters the transceivers? – Sundar Santhanam Jan 08 '21 at 16:13
  • @SundarKrishna That is a new question and should be posted as new question. And you can also download the microcontroller reference manual that explains how the CAN controller works, and you can download the CAN specifications, so asking to explain how CAN works shows no effort really. – Justme Jan 08 '21 at 16:39
  • @SundarKrishna Sent data comes out of the Tx pin and enters through the Rx pin. Not just frames, but also ACK bits etc. These are the local signals of one specific node interacting with the bus. Whereas the data on the actual CANH/CANL signals is broadcasted to every node on the bus - who is the sender depends on the bus arbitration process. – Lundin Jan 11 '21 at 07:39