CAN Loopback on STM32L431KCU Issue

[tom21]

I am trying to get the CAN Loopback up and running on my STM32L431KCU (CAN1), I have tried to follow the: Guide to CAN (bxCAN/CAN2.0) configuration in Loop back mode on STM32 MCUs. But I am getting stuck in the "HAL_CAN_Start()" function where its waiting for the acknowledgement: 

/* Wait the acknowledge */

while ((hcan->Instance->MSR & CAN_MSR_INAK) != 0U)

{

/* Check for the Timeout */

if ((HAL_GetTick() - tickstart) > CAN_TIMEOUT_VALUE)

{

/* Update error code */

hcan->ErrorCode |= HAL_CAN_ERROR_TIMEOUT;



/* Change CAN state */

hcan->State = HAL_CAN_STATE_ERROR;



return HAL_ERROR;

}

}

I then created a new project following the CAN loopback project listed here to get a working project and around my issue: Solved: CAN bus doesn't work in loopback mode - STMicroelectronics Community

Using the same MX CAN config, APB1 of 80MHz, example program, and I still run into being stuck in the "HAL_CAN_Start()". I am using STM32CubeIDE 2.0.0 and MX 6.16.1, any help would be much appreciated.

[mƎALLEm]

Hello @tom21 and welcome to the ST community,

You can refer to this knowledge base article: Guide to CAN (bxCAN/CAN2.0) configuration in Loop back mode on STM32 MCUs

If you followed that guide and didn't work I'm sure you missed something on that guide!

In next time please use </> button to paste your code.

[tom21]

Hi @mƎALLEm ,

I started clean and walked through the guide again step-by-step, did not have any luck it still errors out in the HAL_CAN_START() function waiting for the INAK to clear. Any other suggestions? 

Thanks

[mƎALLEm]

Could you please share your project?

[tom21]

Sure thing, see attached.

[mƎALLEm · Accepted solution]

Hello,

I didn't catch any issue in your code.

The remaining question: is there something connected on PA11 or PA12? if yes, you shoud absolutely disconnect any external hardware from these pins except if you have a CAN tranceiver on these pins.

[tom21]

@mƎALLEm after talking the board layout over it looks like we might have connected PA11 pin to a wakeup pin on another component on the board. Thanks for your help!

[mƎALLEm]

---

@tom21 wrote:

we might have connected PA11 pin to a wakeup pin on another component on the board. Thanks for your help!

---

Indeed that explains the behavior.

I need to update this article (Troubleshooting bxCAN issues in Loop back mode on STM32 MCUs) with this constraint..