Struggling with STM32L432 CAN Bus communication using MCP2551

[Dave001]

Hi all,

I am Struggling with STM32L432 CAN Bus communication from one STM32L432 to another STM32L432 using MCP2551.

* I have checked loopback works.

*I am using HSE Clock (After soldering SB17) - 

* I have also tried putting Oscilloscope at TX pins between STM32 Transmitter and MCP2551 but signal just stays high.

* Plus, i can see that this never triggers but putting it in debug mode and putting a breakpoint in there

I also tried following this guy: 115. STM32CubeIDE MCP2551 CAN BUS with STM32 F103C8T6 

but to no avail. 

* I also tried doing the same setup i.e. ADC on transmitter sending information to other side via CANBUS.

* I have quadrupled checked Hardware circuitry, and all seems to be right.

* CANBUS Distance is also less than a meter now with termination at both ends.

TX Code - 

RX Code - 

Any help would be much appreciated.

Thanks

[mƎALLEm · Accepted solution]

Hello @Dave001  and welcome to the ST community,

First in next time please use </> button to share your code instead of sharing screen shots. Please review how to post a code.

Second, these are a very bad bit timing parameters:

You need to decrease as much as possible the Prescaler and increase as much as possible BS1 and BS2 while having a simple point at around 87%;

Refer to this article: CAN (bxCAN) bit time configuration on STM32 MCUs

This link can help you to calculate the timings parameters. You need to select:

Hope that helps.

[Obaid_tanveer]

You should try playing with the parameters , increase the sample points , use internal/ external loop back mode and see if the RxCallback Triggers, you can refer to https://kvaser.com/support/calculators/bit-timing-calculator/ this website for the CAN bus timing parameters , works well with the ST Boards and is easy to use, You will most likely get the Communication started.

[Dave001]

YOU ARE A LEGEND!!!

Thank you.... i was stuck on this for so long.

[Dave001]

Thank you for commenting, Much appreciated.

Problem is resolved by mƎALLEm.

[Karl Yamashita]

@mƎALLEm 

ST should make an online calculator like http://www.bittiming.can-wiki.info/ or kvaser.

The wiki has been my go to site forever since probably 2005, and with the CAN FD peripherals, I've been using Kvaser