[Elphel-support] Triggered Mode and Linescan together.

[Andrey Filippov]

Hi Brian,

 I did not investigate enough operation of the sensor in triggered mode when
using "linescan" mode. And I do not fully understand all the specifics of
the sensor operation - what it "likes" and what it does not - anyway
internally it is all closed proprietary technology, not everything is
described in the datasheet.

Additionally - when working in triggered mode, there is less
"self-protection" of the camera on the driver level (modifying
user-specified parameters to match sensor/camera capabilities), so it is
easier to put system in wrong state. Basically, when using linescan mode,
the sensor is programmed with the frame size equal to sub-frame, and
TRIG_PERIOD applies to each of the sub-frames.

Do you have the sensor datasheet with the register map? I believe it is now
available for download on Aptina web site w/o registration and signing NDA.
I would recommend you to use parsedit.php to monitor relevant registers of
the sensor (frame size and trigger mode) using SENSOR_REGSnnn (where nnn is
decimal address of the register from the datasheet), you may find some
examples if you open parsedit.php without parameters. It is possible to
modify the register values that way too, but it can cause conflicts with
what driver writes to this registers depending on the settings of the more
general parameters.

FPS reported by camvc in triggered mode may be wrong (it does not measure
the FPS, it reports the guess based on the current parameters, and in some
cases that prediction may be wrong), when using camvc I would recommend to
verify the actual frame rate by pausing the acquisition (controls on the
pink line above the histogram) and navigating the last acquired images with
"<" and ">" buttons (click moves by 1 frame, click with Shift key pressed -
by 10 frames, long press - moves to the first/last frame). When navigating
the frames you'll be able to see each frame timestamp in the yellow fields
above.

Andrey


On Thu, Apr 7, 2011 at 10:40 PM, Brian Burke <burke.brian.a at gmail.com>wrote:

> I'm running 8.0.9.
>
> I'm wondering if anyone can help me understand more how running in
> triggered mode (i.e. TRIG=4) works in conjunction with linescan mode (i.e.
> PF_HEIGHT=2)
>
>  I would like to limit the linescan rate - for example, to 50 linepairs per
> second.  To do this, I set TRIG_PERIOD=1920000 (96,000,000 / 50).  When NOT
> in linescan mode, this seems to work - camvc reports 50 fps.  However, in
> linescan mode, the FPS as reported by camvc does not seem to be limited -
> it's in the 1000's, limited only by the exposure.
>
> Does the TRIG_PERIOD need to be handled differently when in linescan mode?
>  Perhaps some additional math to account for linepairs per composite frame?
> I'm working with a composite frame only 480px high - i.e. 240 linepairs per
> composite frame.
>
>
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