[Gta04-owner] GTA04(A5) Camera (OV9655)

H. Nikolaus Schaller hns at goldelico.com
Fri Jan 20 12:53:17 CET 2017

I took the time while we still have to wait for GTA04A5 production
to continue to take another look into the camera driver.

This time I soldered 5 tiny wires to the camera connector and did
check the signals.

I have seen:
* XCLK: 40ns ~25 MHz
* PCLK: 80ns 12.5 MHz
* HS: negative going impulses (being constantly "L" while VS) with 250µs
* VS: positive impulses with 270ms
* D8: one data line shows random bit patterns which change if I hold a finger on the lens

XCLK should be 24 MHz according to the device tree setup, so OMAP ISP setup is ok!

Since the OV9655 still runs in default initialization (because the
ov9650 driver would write some wrong register values), PCLK is just half
of the required frequency.

Next, I get HS : PCLK = 1 : 3125, which is 1262.5 if we assume 2 bytes
per pixel.

And VS : HS = 1 : 1080.

The camera has an image sensor array with 1300 x 1028 active area.
Therefore, all this looks fine inside the precision of my measurements!

This also means that we are just missing correct setup of the camera chip
(clock and sync polarity and XCLK divider :1).

That needs just some trial and error steps... And a comparison with our old
ov9655 driver.

Since this runs on one of the 3 working GTA04A5 preproduction units, I
think we can now order more camera modules without wasting money...

What I would need is some indication of demand.


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