Hardware camera sync pulses

[6by9]

There have been various requests over the years for external triggers for frame synchronisation. Generally it's been stated that doing such things isn't trivial, and it wasn't. However, as of the 22nd July firmware, there is support for repurposing the camera LED GPIO to change state on frame start and frame end interrupts.....

I don't quite see how this externally triggers cameras, it appears it just shows you when a picture is being taken. Anyone got any details how it can be used to trigger cameras?

It can't be, and I don't think I've ever said it could be.
You can use it alongside the frame rate control to produce effectively a phase lock loop that will pull things in to sync over a few seconds and keep them there.

[gordon77]

There have been various requests over the years for external triggers for frame synchronisation. Generally it's been stated that doing such things isn't trivial, and it wasn't. However, as of the 22nd July firmware, there is support for repurposing the camera LED GPIO to change state on frame start and frame end interrupts.....

I don't quite see how this externally triggers cameras, it appears it just shows you when a picture is being taken. Anyone got any details how it can be used to trigger cameras?

It can't be, and I don't think I've ever said it could be.
You can use it alongside the frame rate control to produce effectively a phase lock loop that will pull things in to sync over a few seconds and keep them there.

Thanks. It looks like I misunderstood "There have been various requests over the years for external triggers for frame synchronisation."

[6by9]

Thanks. It looks like I misunderstood "There have been various requests over the years for external triggers for frame synchronisation."

True, I could have possibly phrased that better - now edited.
This is purely an output which synchronised with frame start/end events as received by the SoC.

[Kozuch]

Do the camera sync pulses also work with the very high FPS mode that user HermannSW showed in the Raw sensor access / CSI-2 receiver peripheral thread? And also here. He claims some 900-1000 FPS.

[6by9]

Do the camera sync pulses also work with the very high FPS mode that user HermannSW showed in the Raw sensor access / CSI-2 receiver peripheral thread? And also here. He claims some 900-1000 FPS.

IIRC then no. They only work with the full camera stack, not rawcam/raspiraw.

[Kozuch]

That really is a pity. Do you think there could be a way to get the closest possible to the moment when a frame is taken in raw camera mode?

[6by9]

That really is a pity. Do you think there could be a way to get the closest possible to the moment when a frame is taken in raw camera mode?

I can do the same thing as for the main stack (it's less plumbing there too), although it still makes little real world sense with a rolling shutter camera where there isn't a single instant of capture.

[Kozuch]

Sync does make a big reason for rolling shutter, especially when combined with a special camera mode (raw in this case) which further shortens the image readout etc. (in low resolution, but that is OK for many computer vision applications). There are also moments when the shutter speed is very short and the rolling shutter is negligible (I can think of a sunny outdoor scene etc.).