External trigger documentation for Global shutter cameras for the raspberry pi 4


I installed the drivers for the OV9821 using UC788 RevB board (SKU: B0224) . Whenever I run libcamera-hello I get a return signal.

Now I would like to try with the external trigger. But, whenever I run v4l2-ctl -d /dev/v4l-subdev0 -c trigger_mode=1 I get the return message: unknown control 'trigger_mode'.

And, in effect, when I run v4l2-ctl -d /dev/v4l-subdev0 --all I see no option to turn on a trigger mode.
(only to change exposure, and flip the image vertically or horizontally)

When I reffer to the documentation, I see only the [B0348], [B0353] and [B0381] as supported SKUs, not mine.

But then, in the same page I see the UC788 and the OV9821 as supported!!

So, I guess I’m having trouble understanding if:

  1. Something went wrong with the installation, despite the fact that I have reinstalled the drivers multiple times

  2. I bought the wrong article, and should’ve bought the supported boards

  3. The documentation is the one that is wrong or out of date.

Also, regarding the documentation:

At the start they say that the voltage of the trigger signal is 1.8V, and that I should convert my 3.3V control signal. But then the connection diagrams show a direct connection from the raspberry pi pins to the XVS pin from the camera module (UC 788) !

Can anyone clarify?

Extra: I choosed to use the OV9821 sensor because it has a high framerate (120 FPS) and a good enough pixel count (1MP). I guess I should choose B0348 if it turns out that I picked the wrong sensor?

Thanks for clarifiying :slight_smile:


The OV9281 sensor with external trigger function is out of stock. You purchased a camera module which does not have trigger mode.

Both 1.8v and 3.3v are okay. You do not need to convert 3.3v to 1.8v if it’s too much trouble on your side.

Maybe B0348 is a good choice for you. It has external trigger mode and a high framerate.

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