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I'm suing TCAN33x from Texas Instruments and it's a 3.3v CAN-bus tranciever. I have succeed to listen for CAN-bus messages from a 24V J1939 CAN-bus stepper motor. Very industrial.

But I haven't succeed to send commands to it. I haven't tried to much to communicated with it. But I notice something in the data sheet of the TCAN33x https://www.ti.com/lit/ds/symlink/tcan334.pdf

CANH will be between 2.45V to 3.3V (Vcc = 3.3) and CANL will be bewteen 0.5V to 1.25V

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But when I searching on CAN-bus signal, the CANL and CANH is much higher than so. For example here CANL is between 1.5V to 2.5V and CANH is between 2.5V to 3.5V

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But still, the data sheet of TCAN33x says.

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Question:

How can 3.3v CAN-bus transceiver communicate with 5 volt CAN-bus transceiver if they are not at the same level of voltage?

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    \$\begingroup\$ The difference between CANH & CANL is much more important than their individual absolute values. \$\endgroup\$
    – brhans
    Jul 12, 2021 at 13:47
  • \$\begingroup\$ @brhans Ahhhh! Now I understand! It's the diff that counts! Thank you. So I can read OBD2 with TCAN33x? If you want, you can write an answer to this question and I will accept it. \$\endgroup\$
    – DanM
    Jul 12, 2021 at 13:52

1 Answer 1

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“ The use of single 3.3-V supply enables the transceivers to directly interface with 3.3-V CAN controllers/MCUs. In addition, these devices are fully compatible with other 5-V CAN transceivers on the same bus”

Page 3 https://www.ti.com/lit/ds/symlink/tcan334.pdf?ts=1626098583867

This is due to the differential voltage method of reception of these signals on a controlled impedance within either common mode voltage.

This IC has a Vcm range of -12V to +12V on the receiver input.

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  • \$\begingroup\$ Thank you for the answer. I assume the TCAN33x will work for all kind of CAN-bus e.g ODB2 etc. \$\endgroup\$
    – DanM
    Jul 13, 2021 at 0:22
  • \$\begingroup\$ It should at the physical layer. \$\endgroup\$ Jul 13, 2021 at 0:44

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