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TMS320F28035: CAN Bus without Transceivers using eCAN

Wayne Huang
Genius 15735 points
Part Number: TMS320F28035

Dear Champs,

I am asking this for our customers.

One of our customers wants to use F28035 eCAN to communicate to another host MCU via CAN on the same board without any transceiver.

We notice there was a discussion about this, but there is no more detail about the physical connection.

e2e.ti.com/.../1613449

We also note that there are at least two articles mentioning this kind of connection so that no external transceiver is needed.

Figure 2 of

http://www.mikrocontroller.net/attachment/28831/siemens_AP2921.pdf

Chapter 2.3 (page 11) in this app note.

https://www.renesas.com/en-eu/doc/products/mpumcu/apn/rl78/001/r01an2535ed0200_can.pdf

It appears the connection by two external diodes and one pull-up resistor on both Tx pins can work.

Therefore, we'd like to confirm again with you.

Do you think this connection also works for eCAN of F28035/F28069?

Or is there any hardware difference of the eCAN module so that we cannot use it like that way?

Wayne

 

  • 0
    Guru 192875 points

    Hi Wayne,

    Wayne Huang said:

    Do you think this connection also works for eCAN of F28035/F28069?

    There have been many discussions on this topic and it seems that its possible to communicate without transceiver but I'm not sure the same is recommended by experts! As for a hobby tryout it sounds fine but not for any commercial product. eCAN peripheral is always expected to accompany with a transceiver. 

    can you shed some light here :)

    Regards,

    Gautam

  • 0 in reply to Gautam Iyer
    TI__Guru* 95315 points

    Wayne,

                Although I have not tried this myself, I don’t see a reason why the method suggested in the app.notes (or the other thread you refer to - with an AND gate) would not work. The CAN pins in our devices are functionally the same as those found in any other MCU (with the exception that VOH spec may be different, based on the supply voltage of the MCU in question). Remember they all need to conform to the CAN protocol, which is an industry standard. When using discrete passive devices, ensure VIH/VIL specifications of the CANRX pin are observed.

  • 0 in reply to Hareesh Janakiraman
    TI__Genius 15735 points

    Hareesh,

    Thank you for your information.

    We will try to validate it.

    Wayne