April Tags with MT9V034

I am completely new to the world of OpenMV and I try to find out how I can use it for April Tag detection. I am using:
OpenMV Cam H7 Plus with the MT9V034 Module
But all examples are not working. It only shows “ValueError: Sensor control failed!”
What can I do to make the examples work? Any hints are very welcome.
Thanks and regards!

I have experimeted a little and in order to bring it to work I have to remove:

sensor.set_auto_whitebal(False) # must turn this off to prevent image washout…

Is there any documentation for the MT9V034 software functions?

Not really, we didn’t implement functions which don’t make sense for a grayscale camera.

Thank you for your quick answer!! The function:
also does not work with MT9V034 but with OV5640. Or is there something special to get the read-out window for this camera!

That’s not implemented. However, we should implement it. It would make the sensor more useful.


I am just about to start experimenting with my OpenMV H7 and I was wondering whether I need the H7 Plus to track April Tags or if I could use my H7, too. Unfortunately whenever I want to use the given example in OpenMV IDE, " ValueError: Sensor control failed!" occurs.

Thanks a lot in advance for your support.

Hi, just remove the offending line. The MT9V034 doesn’t support turning auto white balance off.

Hi, please guide me how to do auto zoom and auto focus on SMT32H7 device. In my project i need to add this option. please guide me how? please provide some example code for auto zoom for particular threshold color.

The lens doesn’t have that ability… so, not sure how you are going to do it.

Sorry i am using OpenMV Cam H7 Plus with lenses. for these i want to do auto zoom and auto focus using script. please help me how i do?

Hi, do you have a lens that can zoom? Because without that you can’t do either of those things.

Yes i have lens for doing zoom and focus this.

Okay, so, I can’t help you explicitly, with code, but, I would first figure out how to control the zoom on the lens using the camera and how to control the focal length to control focus.

Once you have that zoom in straight forward for tracking an object. Auto focus however requires something else called the MTF which we do not support right now.

okay. Thanks you for your support.

Hi, i have one doubt. is there any chance to take “adaptive threshold values” while camera will doing his job.?

AprilTags internally adaptively thresholds the image.

thank you. i will try ariltag concept… its realy good.

How to control motorizes lens in openmv H7.? Here we have two separate motors to control Zoom and Focus.

By what method are the lenses attached to the OpenMV Cam?

E.g , are they servo controlled, or 2 wire motors?

Its an stepper motors…
Model is CW0550FB.IR-JZ-2MP