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Running a camera without a screen?

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Offline arsenix

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Running a camera without a screen?
« on: 21 / April / 2015, 21:59:52 »
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I am trying to strip down a cam (in this case a Powershot A4000) and run it remotely through chdk/ptp/usb. The remote operation works great, but as soon as I disconnect the screen it stops working. It appears to me that the camera is crashing or otherwise shutting down after a second or so when the screen is disconnected. The lens assembly moves a bit, but then it all stops.

It looks to me like there may be a temp sensor embedded in the flex cable of the screen. Could this be the issue? Maybe the cam thinks it is overtemping?

Any ideas how to get this to work?
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Offline waterwingz

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Re: Running a camera without a screen?
« Reply #1 on: 21 / April / 2015, 22:07:15 »
So if I understand this correctly,  you are disconnecting the camera's LCD display while the camera is powered up and running?  There are so many things that can go wrong with that plan - especially if you disconnect the ground connection first as you pull the connectors apart.

So I guess my first question is - why are you trying to do this in the first place?  Battery life?  If so,  a small external battery seems like a much safer choice - especially as the LCD display just doen't draw all that much power when CHDK tells it to turn off.
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline Hardware_Hacker

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Re: Running a camera without a screen?
« Reply #2 on: 21 / April / 2015, 22:35:43 »
Quote from: arsenix on 21 / April / 2015, 21:59:52
Any ideas how to get this to work?

It works Ok, for me, with an Ixus 115 with the LCD Display already disconected at Power-Up time.
I used a older version of ChdkPtp, for remotle controll of the Ixus 115's, when I doing this some time ago.
The Ixus Cameras just worked in same way as if the LCD Display was already connected.

The main reason for trying this was I was planing to mount the cameras "Back to Back" and so the
the camera lenses would then be "Co-Axial".
 
Access to the LCD Display's and the Back Panel Switch's would not then be possible unless I extended the
cables etc.

H-H
« Last Edit: 21 / April / 2015, 22:49:44 by Hardware_Hacker »
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Offline arsenix

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Re: Running a camera without a screen?
« Reply #3 on: 21 / April / 2015, 22:49:16 »
Oh no I'm not disconnecting it while it is running. I am trying to boot it without the screen in the first place. The idea is to make the cam smaller for a multicam setup. I am also ditching the case and essentially everything except the lens and mainboard. It all works other than the screen part.

Not sure why it would crash with the screen disconnected. I suppose I could connect to the UART and see if there is anything revealing in there? Bit of a catch 22 since I am sure there is some error message on the screen!
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Offline waterwingz

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Re: Running a camera without a screen?
« Reply #4 on: 21 / April / 2015, 22:52:22 »
You could try doing a ROM crash log and post it here.  From the CHDK main menu go to the Miscellaneous Stuff menu and then to the Debug Parameters menu.  Select Save ROM crash log.  Then look in the root of the SD card for a file calle ROMLOG.LOG and post it here?

The camera will hold the most recent crash log so you can reconnect the LCD with the power off and use the CHDK menus to retrieve it.
« Last Edit: 21 / April / 2015, 22:54:11 by waterwingz »
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline reyalp

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Re: Running a camera without a screen?
« Reply #5 on: 21 / April / 2015, 23:09:46 »
Quote from: arsenix on 21 / April / 2015, 22:49:16
Oh no I'm not disconnecting it while it is running. I am trying to boot it without the screen in the first place. The idea is to make the cam smaller for a multicam setup. I am also ditching the case and essentially everything except the lens and mainboard. It all works other than the screen part.
It doesn't surprise me at all that having the LCD disconnected would trigger an error, there's an LCD controller that expects to talk to a working screen.

It's possible (though unlikely, IMO) that having something plugged into the video out would make the camera never try to initialize the LCD, but unfortunately the A4000 doesn't support shooting while connected to external video, so it still wouldn't solve your problem.
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Offline arsenix

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Re: Running a camera without a screen?
« Reply #6 on: 21 / April / 2015, 23:18:22 »

Most LCD interfaces are one-way, so I figured it would work fine. Maybe there is a "detect" pin of some kind in the harness that I could spoof? Is the LCD controller the Digic processor?


Hmm RomLogErr.txt just says "Log is not saved". Tried it a few times.

Guess this means the crash occurred before CHDK starts?

Appreciate the help here!
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Offline Hardware_Hacker

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Re: Running a camera without a screen?
« Reply #7 on: 21 / April / 2015, 23:53:34 »
Quote from: arsenix on 21 / April / 2015, 22:49:16
The idea is to make the cam smaller for a multicam setup. I am also ditching the case and essentially everything except the lens and mainboard. It all works other than the screen part.
What is your Multi-Camera rig going to be used for?.
How "smaller" can you make your Multi-Camera rig?.

H-H
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Offline reyalp

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Re: Running a camera without a screen?
« Reply #8 on: 22 / April / 2015, 00:03:44 »
Quote from: arsenix on 21 / April / 2015, 23:18:22
Guess this means the crash occurred before CHDK starts?
The romlog is a canon firmware feature, so it means the canon firmware did not generate a romlog for whatever error caused the shutdown.
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Maybe there is a "detect" pin of some kind in the harness that I could spoof?
I wouldn't expect a dedicated "detect" pin, more likely some specific conditions are expected. Presumably, it can be spoofed with enough effort.
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Is the LCD controller the Digic processor?
I would expect it to be separate IC.

Sometimes you can find canon factory service manuals on google. http://photo-parts.com.ua/parts/dbphp.php?part=Canon%20A4000 may also be useful.
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Offline waterwingz

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Re: Running a camera without a screen?
« Reply #9 on: 22 / April / 2015, 00:07:54 »
Quote from: arsenix on 21 / April / 2015, 23:18:22
Hmm RomLogErr.txt just says "Log is not saved". Tried it a few times.
Guess this means the crash occurred before CHDK starts?
That's a curious result. 

AFAIK (and I just did a bunch of grepping of the CHDK source to confirm it) the only thing that will produce a RomLogErr.txt file is the obsolete test script romlog.lua.

The menu sequence I posted for you will not.  It should produce a file called ROMLOG.LOG (as I stated).

Are you sure you used the steps I posted?

Edit : never mind - reyalp informs me that the Canon firmware will create that file if there is no info for a ROMLOG.LOG file.

« Last Edit: 22 / April / 2015, 00:22:49 by waterwingz »
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Ported :   A1200    SD940   G10    Powershot N    G16
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