CAN bus without transceivers

According to Siemens application note AP2921 On-Board Communication via CAN without Transceivers all Rx and Tx lines shall be connected to a single data line pulled up to VCC. Though Tx outputs shall be connected through fast diodes rather than directly to avoid short circuits at the output pins. Such simplified circuitry is suitable when CAN devices are located close to each other, for exapmle on the same card or in the same rack.


Make sure that +3.3V is used as pull up voltage with MBED boards (rather than +5V)!
It is also very important that the current at one port pin does not exceed 1.6 mA.


4 comments on CAN bus without transceivers:

16 Mar 2020

It works at a speed of 20 - 50 - 100k.

Line Length 2 * 1.5m.

I have only 2 devices STM32F103C8T6 (as NUCLEO-F103RB)

CAN can(PA_11, PA_12); pin for CAN Rx/Tx

27 Mar 2021


08 Apr 2021

Hi what did you use for diode ?

ı mean how much voltage value in diode

19 Jun 2022

Use the following link to view the Siemens Application note AP2921:

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