Grove Vision AI V2 - Save Image to SD CARD

Products & Technology Grove
1

@PJ_Glasso I have a RAK 3172 (STM32WL uP) successfully operating the WE2 via commands via I2C communications, running a model and returning results. The WE2 contains SSCMA-Micro. I’ve referred to SSCMA-Micro GitHub at_protocol, but have yet to be able to cause an image to be stored to the SD CARD. Note, I am not using the Arduino based SSCMA library (as it does not currently support the SMT32 family). I have tried various iterations of AT+SAMPLE and AT+TRIGGER and AT+INVOKE (which can send images files via a serial link).
Do you have any guidance on command(s) needed to have the SSCMA-MICRO firmware store an image file to the on-board SD Card?
Thanks in advance!

2

Hi there,

So I have NOT tried this Myself but AFAIK it works,
SSCMA-Micro does support saving JPEGs to the module’s SD card, but it’s not done with AT+SAMPLE / AT+TRIGGER / AT+INVOKE by themselves.

On Grove Vision AI V2 (WE2 + SSCMA-Micro), SD saving is driven by an “action trigger”:

The command you want

AT+ACTION="save_jpeg()"\r

Set the action once:
Seeed’s docs explicitly say that calling save_jpeg() sends AT+ACTION="save_jpeg()", and it “should only be called once.”

Then: every INVOKE will save a JPEG

After the action is set, each time you invoke (i.e., run the pipeline), the module will save a JPEG to the SD card. The Seeed example literally does: AI.save_jpeg(); once in setup, then AI.invoke(...) repeatedly, and “each invoke saves JPEG.”

So from your STM32WL/RAK3172 side, the flow is:

  1. Once at startup:
AT+ACTION="save_jpeg()"\r
  1. hen repeatedly (whatever your normal run command is):
  • AT+INVOKE... (or the equivalent you’re already using successfully)

To stop saving (important)

You must clear the action set (even after reboot, per the docs):crossed_fingers:

AT+ACTION=""\r

Seeed notes this is equivalent to clean_actions() and must be done if you no longer want JPEGs stored.

SD card “gotchas” that matter

If they still don’t see files:

  • SD must be FAT32 (with 8192 cluster size) or exFAT (Seeed recommendation).
  • Firmware needs to be new enough (Seeed calls out later than 2024-04-18).
  • Files go under a default export folder; the system creates session subfolders and tracks the latest folder in a hidden .sscma file (don’t edit it).

Those are about capturing/streaming/returning images (e.g., base64 over UART) — they don’t automatically configure the “save-to-SD” action. The SD write is specifically tied to the ACTION trigger mechanism.

HTH
GL :slight_smile: PJ :v:

Time permitting I’ll check it out, as I do have a use case for it. :+1:

3

@PJ_Glasso I will test with the guidance you have provided.

Please share the link to the Seeed’s doc you mention and the Seeed example that uses the AI.save_jpeg();. I went through the Wiki again and the GitHUb of SSCMA-Micro but did not come across it?

Additional comments. I was able to implement the AT+ACTION both to start saving to the SD CARD and to stop it, as you suggest, hooray!

However, the images are low resolution (~3KB). Is there a way to save the full resolution image sense by the OV5647 camera?
Thanks!

Jim M

4

Hi there,

So, this would be that :grin:

Example 3.

I would think you can set the default to be Higher maybe.

HTH
GL :slight_smile: PJ :v:

5

The command you need is AT+ACTION="save_jpeg()", followed by your standard AT+INVOKE command. This is not done with AT+SAMPLE or AT+TRIGGER alone .

The key is that the SSCMA-Micro firmware on your WE2 uses an “action trigger” system for SD card saving. You set the action once, and then every subsequent inference will save an image.

1 Like