How can I contact smt32f103vc and stm32f407 with CANBUS protocol without transceiver?

[kadir ustun1]

Hello everyone,

I want to contact STM32F103VC and STM32F407 with canbus protocol without transceiver.

I set baudrate 60kHz. but I can not send or receive data. Can you hel please ?

Thank you.

[Ozone]

Should work at least for short distances.

Have you tried the devices separately, in loopback mode ?

[kadir ustun1]

in loopback mode stm32f103 is taking own value.

[Ozone]

Yes, I know.

If you receive you own transmissions, cross-connecting the Tx/Rx lines to the other device would be the next step.

I hope you did not forget a GND connection, if the devices don't share a common GND on one power supply.

[kadir ustun1]

Actually, stm32f407 is working another bord. but I havent tried stm32f103 yet. Distance is short.

[Tesla DeLorean]

Keil published a method using diodes to achieve a low-cost CAN connection.

http://www.keil.com/appnotes/docs/apnt_236.asp

http://www.keil.com/appnotes/files/apnt_236_v2.9.pdf

See "Tiny Network without Transceiver ICs"

[kadir ustun1]

I did circuit. But I can not send data.

[Tesla DeLorean]

Does it gives some error or status indication?

A CAN transmitter needs a responding node. You'd need a receiving device with the matching baud rate to acknowledge the packet.​

[kadir ustun1]

Hello again.

I try to do this on cubemx. Now, I can send data but I can not receive data. I compare F4 and F1. And I saw that F4's rx pin mode: "alternate function push pul" but f1's rx pin mode :"Input mode". When I cahange it as alternate, Canbus does not init. so I think does not f1 work without tranciever. What do you think about that ?