Strobe / sync output

cnolan

Hi all. I'm testing an OAK-D Pro W PoE, in particular the hardware sync capabilities. Hooking up a scope to either the strobe or the sync pins of the M8 port, I seem to be recording an ₅₀ Hz strobe cycle regardless of what frame rate I set for capture. The documentation suggests the strobe channel (as output on the M8 port) should be driven by the left mono camera capture, but I've tried setting all frame rates and I can't seem to change the strobe channel frequency. Am I missing something here?

erik

Hi cnolan ,
Strobe is PWM, could you elaborate on the scoping approach you have used? Have you connected the GND? What kind of signal are you seeing (the 50Hz), could you share an image?
Thansk ,Erik

cnolan

Thanks @erik, I've connected the scope ground to the OAK-D's isolated ground. From memory the FSYNC signal had a 3V amplitude which seems correct, just not at the frequency I was expecting. I'll set it up again and share an image when I can later today.

Am I correct that the left mono camera frame rate should govern this cycle?

erik

Hi cnolan ,
Yes you are correct, left mono cam governs the cycle. And please do share an image, it would be really helpful for debugging!
Thanks, Erik

cnolan

So if I hook up a scope directly to the output (isolated ground to strobe), I seem to get a very noisy 50 Hz signal (i.e. power freq).

David

Hi cnolan,

I am sorry about the issues you are experiencing here with this strobe signal functionality.
Can you please let me know which version of the product you have in hand if that is easy for you to check?
The version is printed on the PCB, so you would need to open the enclosure to check it though.
Please note that calibration will be lost if you do that, and if that is not something convenient for you to do please don't we will work on locating the issue today anyway.

Thanks,
David

cnolan

Thanks David, I would prefer to not do that right now if I can avoid it. The device was only shipped a little over a week ago if that helps.

Just to explain what I'm trying right now. I've checked out and installed the multi_cam_support branch of depthai-python, and I'm setting the frameSyncMode of the left mono camera to OUTPUT and testing the FSYNC vs. isolated ground on the scope. I'm getting the same result as above.

cnolan

Incidentally, if I try to set the strobe to sensor using:

ctrl = dai.CameraControl()
ctrl.setStrobeSensor(1)
controlQueue.send(ctrl)

I get an error:

[18443010313CC51200] [169.254.1.222] [13.481] [system] [critical] Fatal error. Please report to developers. Log: 'DrvGpio' '326'

David

@cnolan FSYNC is meant to be used as an input so you can sync multiple devices from the outside. I am not sure what are you measuring but that is definitely not a FSYNC signal, as you can't measure the FSYNC which is isolated. Below is the schematic of that part on OAK-D-Pro-PoE
FSYNC signal is by its function just a pulse that is driven high at the start of the frame capture and not a PWM signal with the on time same as exposure time.
STROBE is an output that is meant to be used as an output and you could drive, so yes setting strobe on LEFT camera and measuring the STROBE on the connector would do it.
Thoughts?

David

I am not sure what is the reason for an error you get though, @erik might be able to give you an answer right away.

David

@cnolan we measure the STROBE output and it works in our case on the sample we have in the office, can you check on your side if yo get the same?

cnolan

Hi David, the first scope image I sent was between the strobe - isolated ground pin.

cnolan

Just to clarify, is there anything specific you need to do in the pipeline to enable the strobe pin output? And the device you were using in your test there was a OAK-D Pro W PoE?

David

@cnolan we tested on OAK-D-Pro-W and just a note you should add PU resistor to the output if you haven't done so, as this is open-collector output.
We did simple test with depthai-demo.py just simply running the camera and the output is already set on camera driving the strobe.

cnolan

Hi David, that'll be the issue, I've been expecting a TTL pulse. Is there a supply line as well I can use for pull-up, or do I need an external supply?

cnolan

That was the problem, thanks David. Annoying mistake on my part sorry, should have looked at the strobe circuit diagram.

David

@cnolan no worries, and thanks for circling back!

Regards,
David

K-LReinhard

Hi,

how did you solve the issue? What values for a pullup did you use?

K-LReinhard

@cnolan What values did you use? I'm not sure how you solved the problem finally. It would help us a lot!

erik

@K-LReinhard could you share your setup / script and all the details? Perhaps we can help as well🙂

K-LReinhard

erik thanks for circling back!

Overall we want to drive an external strobe light. If I'm reading the circuit diagrams correctly this should be possible with the strobe output(decoupled via optocoppler).

Maybe before I describe our setup in details: do I need to explicitly enable the strobe output via python code?

What about the open collector output and the pullup resistance?
For the m8 connector is there a specific color coding which color is the strobe output and isolated gnd(maybe for the included m8 cable)?