TMS570LS0432: CAN Communication between two LAUNCHXL-TMS57004

Kartik Shanbhag18

Part Number: TMS570LS0432
Other Parts Discussed in Thread: LAUNCHXL-TMS57004, , HALCOGEN

Hello.

I am using two LAUNCHXL-TMS57004 launchpads (TMS570LS0432) and want to communicate between them using CAN. I am following the instructions as given in this Hercules CAN tutorial: https://training.ti.com/hercules-how-tutorial-can-communication

I have a few queries regarding the hardware connections:-

1) Without a transceiver, is it possible to communicate by connecting the CAN1TX to the CAN2RX of the same launchpad (it has two CAN ports)?

2) Without a transceiver, is it possible to communicate by connecting the CAN1TX of one launchpad to the CAN1RX of the second launchpad?

The launchpads do not have inbuilt transceivers and hence I am asking these questions. Is it all at possible to test CAN communication without the transceivers?

Thank you in advance.

Kartik

over 7 years ago

0 Miro over 7 years ago

TI__Mastermind 21425 points

Hello Kartik,
You will need transceivers in both cases. CAN is a serial, two-wire, differential bus technology. While transmitting data CAN node is also reading current bus state, something you can't achieve with connecting Rx and Tx. On the web you could find some solutions that might work but I am not sure whether they are fully compatible with CAN protocol.
Here you can find some transceivers:
www.ti.com/.../SN65HVD232
www.ti.com/.../products.html

Best regards,
Miro

0 Kartik Shanbhag18 over 7 years ago in reply to Miro

Intellectual 600 points

Thanks for the clarification.
What you have said applies even to the Loopback mode right?(Present in the Example section in HALCOGEN).. Even in the simple loopback mode, we need to have a transceiever for CAN to work.

0 Miro over 7 years ago in reply to Kartik Shanbhag18

TI__Mastermind 21425 points

Kartik,
Loop back mode could be used without transceivers. In loop back mode CAN Core ignores acknowledge errors.
You can find more info about test modes in section: 20.2.14 Test Modes (page 813 of TRM).

Best regards,
Miro

0 Kartik Shanbhag18 over 7 years ago in reply to Miro

Intellectual 600 points

Thank you for your help.

0 Jan Cumps over 7 years ago in reply to Kartik Shanbhag18

Guru 15740 points

If you want to try out CAN without the drivers, there is the possibility to try it out with the help of two diodes and 1 resistor.
This is not for production use, but it allows to exchange the data for test and learning purposes. I've written down a short how-to.

0 Kartik Shanbhag18 over 7 years ago in reply to Jan Cumps

Intellectual 600 points

Thank you. I will try this this out.

0 Kartik Shanbhag18 over 7 years ago in reply to Kartik Shanbhag18

Intellectual 600 points

Hello.
I checked using the above circuit. It worked. I was able to communicate via CAN without transceivers.

Thank you for your help. Jan Cumps

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TMS570LS0432: CAN Communication between two LAUNCHXL-TMS57004