On-Board Communication via CAN without transceiver

Forum|Forum|4 years ago
September 30, 2021
3 replies
6323 views

Two CANs on the same board. Can I connect CAN1TX to CAN2RX and CAN1RX to CAN2TX?

CAN

This topic has been closed for replies.

Javier1

Principal

Never tried it myself but why not, try with some diodes and a pullup resistor.

The canbus line needs to be pulledup high when idle(pullup resistor, if your chips logic is 3v3, use 3v3 for the pullup)

The Rx and TX need to be conneted together, so we need a diode to avoid Tx lines to spill their voltage and mess with the bus.

https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/605836/tms320f28035-can-bus-without-transceivers-using-ecan

hit me up in https://www.linkedin.com/in/javiermuñoz/

Tesla DeLorean

Guru

Keil has white papers on this and on STM3

Tips, Buy me a coffee, or three.. PayPal Venmo (See Profile) Up vote any posts that you find helpful, it shows what's working..

MissionYEAuthor

Associate II

Thanks

Didier_G

ST Employee

The approach looks valid for low bitrates only.

Tesla DeLorean

Guru

Bob suggests it's certainly viable to 500 Kbps on small boards

https://www.keil.com/appnotes/files/apnt_236.pdf

Similar mechanics could be applied to UART single wire bus.

Tips, Buy me a coffee, or three.. PayPal Venmo (See Profile) Up vote any posts that you find helpful, it shows what's working..

Didier_G

ST Employee

This speed is far from being confirmed and this trick is probably not viable in production (automotive grade, noise immunity, etc ...).

Schottky diodes with fast transient response are required. The pull-up value has probably to be decreased if the number of controllers increases, for smart edges.

Sign up

Login with SSO

Login to the community

Login with SSO

Scanning file for viruses.

This file cannot be downloaded