STM32N6 NUCLEO - Infinite loop issue in LL_ATON_RT_RunEpochBlock() during NPU inference

[Student_0726]

Hello,

I am currently experiencing difficulties using the STM32N6 NUCLEO board.

My goal is to test NPU execution using X-CUBE-AI within CubeMX. However, I am stuck in an infinite loop inside the MX_X_CUBE_AI_Process function. Specifically, LL_ATON_RT_RunEpochBlock() continuously returns only the LL_ATON_RT_DONE status, preventing the loop from terminating as expected.

do {

ret = LL_ATON_RT_RunEpochBlock(&NN_Instance_Default);

if (ret == LL_ATON_RT_WFE) LL_ATON_OSAL_WFE();

} while (ret != LL_ATON_RT_DONE);

I Can't get the LL_ATON_RT_DONE, only LL_ATON_RT_WFE.

This issue persists even when using files generated via Cube AI Studio.

I have configured the AXI and Clock settings in CubeMX (CPU: 600MHz, NPU: 800MHz, AXI: 800MHz). Since the model is simple, I am using internal memory only and have not enabled any security (TrustZone) or external memory settings.

Environment Versions:

• CubeIDE: 2.1.1

• CubeMX: 6.16.1

• CubeAI Studio: 1.1.0

• CubeProgrammer: 2.22.0

• ST Edge AI: 4.0

• ST-LINK: V3J17M10

I have attached one of the project files I’ve been testing. It would be a huge help if you could guide me to a solution for this issue.

[hamitiya · Accepted solution]

Hello @Student_0726,

I don't have any issue doing so with the debugger, with STM32N6570-DK and NUCLEO-N657X0-Q.

On your side, are you working through the debugger or through loading scripts?

Is your board having correct power supply ? You should have the a green color in led LD4. If it is orange, it means the power is not sufficient.

Best regards,

Yanis

[Student_0726]

@hamitiya Thank you for the reply.

I checked your feedback and tried running it again—now it passes through correctly!

I was testing in the CubeIDE debug environment, and the LD4 green LED was on as expected.

Honestly, I’m not sure why it’s working now, as I haven't changed any code and the USB connection wasn't unstable before. It’s a bit mysterious why it was consistently failing earlier but works fine now.

I feel a bit bad for taking up your time with this, but I'm just glad it's resolved! Now I can move forward with my experiments with a much lighter heart. Thank you again!

[hamitiya]

Hello @Student_0726 

No problem! Glad it helped!

Feel free to ask again if you have any questions :)

Best regards,

Yanis

[Student_0726]

I’ve discovered a new issue with the test code I posted in my previous question.

To verify the NPU operation, I modified the input values and checked for corresponding changes in the output. However, I noticed that the output values remain unchanged regardless of the input.

I would like to know if I have misconfigured the AI Process structure or if there is an error elsewhere in my setup.

I feel like I'm missing something small, yet I'm still stuck. It’s a bit frustrating.