Connecting two Pmod CAN together

[digitalone]

The Pmod CAN has a DB9 connector. 

Can two of them be connected directly together via a null modem RS232 cable to allow them to communicate?

If not, how could two of them be connected together to allow them to communicate with each other?

Is there a termination resistor already on the Pmod CAN?

 

[JColvin]

Hi @digitalone,

They should be able to be connected directly together without issue via a RS232 cable, yes.

Each Pmod CAN has a jumper (JP1) to optionally enable the 120 Ohm termination between CANH and CANL, as well as an additional JP2 jumper to optionally terminate the lines with a capacitor to ground. You can see the setup in the Pmod CAN schematic, https://digilent.com/reference/_media/reference/pmod/pmodcan/pmodcan_sch.pdf, which can also be found on the right-hand side of the Pmod CAN Resource Center: https://digilent.com/reference/pmod/pmodcan/start.

Let me know if you have any questions.

Thanks,
JColvin

[digitalone]

Thank you.

So for a direct connection between two Pmod CAN units via RS232 null-modem cable, I would enabled the jumper to apply the 120 ohm termination.

For this setup, do I also need the capacitor load applied too?

[JColvin]

Hi @digitalone,

For the split termination setup that is used on the Pmod CAN (both ends terminated if they are the ends in your system), my understanding is yes you will want to use JP2 to enable the capacitor load, at least based on this TI App Note (section 4.5.2), https://www.ti.com/lit/an/slla270/slla270.pdf, which is also reiterated in this Technical Article from TI here, https://www.ti.com/document-viewer/lit/html/SSZTB40.

Let me know if you have any questions.

Thanks,
JColvin