openMV N6: ml.Model() hard fault / DFU reboot when loading custom INT8 TFLite from ROMFS on N6

OpenMV Boards
1

Hi,

I’m deploying a custom INT8 TFLite classifier model on the OpenMV N6 (firmware 4.8.1 latest) and hitting a hard fault / DFU reboot loop when calling ml.Model() on my ROMFS model. I also get “database error” after that. The built-in ROMFS models load fine, so it appears to be specific to my model. FYI I uploaded and committed my model using the Edit ROMFS method on to my N6 device. I saw the similar issue with the exported Edge impulse tflite models too.

Hardware: OpenMV N6, STM32N657X0, PAG7936 sensor, firmware 4.8.1

Model details: 3-class classifier, 64×64 grayscale input, INT8 quantized
Architecture: Conv2D(8) → MaxPooling2D → Conv2D(16) → GlobalAveragePooling2D → Dense(3)
Original .tflite size: 5.0 KB
After ROMFS commit: 18,480 bytes — IDE NPU conversion appears to have succeeded

Is it possible to tell what could be the issue?

Is there a list of supported ops for NPU conversion on the N6?
Is there a way to run a ROMFS model on the CPU TFLite interpreter instead of the NPU, as a fallback?

Thanks

Swathi

2

You need to do Tools->Install the Latest dev firmware release for the N6 in OpenMV IDE. Then it will work. We are getting very close to releasing v5.0.0.

3

Thanks for the reply. I think I did install the latest dev firmware as you mentioned before loading the models through ROMFS. It is 4.8.1 (latest) as shown in the screenshot below:

database error
database error1918×1143 223 KB

4

Now I tried again Installing the latest dev release. First, I saw version 5.0.0 in the bottom status bar on the IDE as shown below:

image
image1915×1036 158 KB

But after rebooting, it went back to 4.8.1 version and then I started hitting the hard fault and DFU reboot again, now even with loading the in built rom models as shown below:

image
image1737×999 143 KB

How to recover my N6 device from this state?

Thanks

Swathi

5

Hi, did you install the factory version of the IDE? The registered board label shouldn’t appear in the normal user version.

Can you grab some time on my calendar, and I’ll help you through this: https://calendar.app.google/AonJZLcTwD2Fo4TM7

The board is fine. Just want to see where you are getting stuck.

6

I think I installed the wrong IDE - i.e, factory version. Now I uninstalled it and reinstalled the user version and reloaded everything. Loading custom models is working fine now. I think I don’t need an appointment for working on this issue anymore, as it is resolved. Can you please cancel the appointment that I booked at 3 PM PST today.

Thanks

Swathi

7

Cool, great!