[Elphel-support] External triggering

[Ángel]

Thank you very much, Oleg & Andrey.

I'm in the process of understanding the camera. Since I have access to a
digital sampling oscilloscope I would like to play a little with triggering.

So, what pins of J15 must I connect the signal and ground wires of the
function generator output to?

Thank you, again.

Ángel.

2010/2/2 Andrey Filippov <andrey at elphel.com>

> Ángel,
>
> Couple more notes about external triggering.
>
>  This is a "Electronic Rolling Shutter" sensor, so there are some natural
> limitations on what you can do with external triggering. If you want just to
> synchronize two cameras - it is easy, but you can not trigger the camera
> that way from a flash (there are some other ways how to do that). External
> trigger on the sensor level work in the following way:
> 1 - sensor waits for the trigger to occur, to data and sync signals are
> output
> 2 - after the trigger sensor skips 8 scan lines (for some internal reasons)
> 3 - sensor _starts_ to erase scan line - one by one - the it will take
> about 1/15 seconds to clear the full 5 MPix frame
> 4 - after waiting specified exposure time from start of the erasing process
> (sensor does not need to wait the full frame to be erased!) sensor starts
> readout - line by line, at the same pace the erase process (initiated at
> step 3).
> The process of readout (and so exposure of the last line in the frame) will
> ens in 8*scan_line_time + exposure time + frame_readout_time.
>
> If you want to catch some instantaneous event (i.e. flash) you'll need to
> set exposure time to > frame readout time and initiate that event after the
> full frame is erased but before the first line is read out.
>
> Second note is related to the camera driver - because of pipeline operation
> (described in
> http://www.linuxfordevices.com/c/a/Linux-For-Devices-Articles/Elphel-camera-under-the-hood-from-Verilog-to-PHP/) it heavily depends on the frame sync pulses from the sensor. So if the
> sensor is stopped so is the driver that among others handle all the
> parameter changes. If the camera is set to external trigger mode and there
> is no trigger coming - the driver will effectively get stuck.
>
> Andrey
>



-- 
Elphel NC353L-369 (12-36 VDC) + Computar H2Z0414C-MP
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