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USB Download

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Offline stagdriver

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USB Download
« on: 01 / April / 2014, 18:24:36 »
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Good evening all.
I have been reading about USB but i cannot find a definitive answer to my question.

Is it possible to have a USB cable permanently connected to a camera in timelapse running ultimate intervalometer, (lets assume the camera is in a hermetically sealed box with usb to the outside world), but only connect a laptop to download say every couple of weeks without touching the camera buttons or turning chdk off. Wll the laptop connect / disconnect without interrupting chdk or it it mandatory to stop chdk first?.
Bit loathed to just try it in case of damage.

There are some discussions out there but most seem related to a pc being permanently tethered.
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Offline reyalp

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Re: USB Download
« Reply #1 on: 01 / April / 2014, 21:45:58 »
Quote from: stagdriver on 01 / April / 2014, 18:24:36
Good evening all.
I have been reading about USB but i cannot find a definitive answer to my question.

Is it possible to have a USB cable permanently connected to a camera in timelapse running ultimate intervalometer, (lets assume the camera is in a hermetically sealed box with usb to the outside world), but only connect a laptop to download say every couple of weeks without touching the camera buttons or turning chdk off. Wll the laptop connect / disconnect without interrupting chdk or it it mandatory to stop chdk first?.
There are ways this could be done, though at a minimum it will probably require modification to the script.

Normally, when you connect a PC to the cable, the camera will switch to PTP mode, retracting the lens and possibly shutting off the screen. (some old cameras with a hardware play/rec switch will just ignore the USB connection). Switching to PTP mode would probably confuse the script if it happens in the middle of shooting a timelapse. The script could be made to detect the presence of USB power and stop shooting, but I"m not sure what happens if you plug in while in the middle of a shot. If this is a problem, you could probably use the usb remote setting to ignore the USB connection in the shooting cycle and just check for USB power periodically in between. (USB remote is usually used for the the DIY hardware remote http://chdk.wikia.com/wiki/USB_Shutter_Remote but it also hides the presence of USB from the camera firmware. The remote setting can be changed from script using set_config_value)

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Bit loathed to just try it in case of damage.
Chances of actual damage to the camera should be extremely low. At the worst, it wouldn't run as expected and you lose some data.
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Offline stagdriver

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Re: USB Download
« Reply #2 on: 02 / April / 2014, 06:57:55 »
Thanks for the advice.

I think this may be a case of "dont fix what aint broken".
I am thinking in the short term i will make the camera more accessible to remove the sd card and download without altering the camera position. (probably just power control and set to run script automatically on power resume).
May investigate having a small intel atom pc permanently attached but power consumption would be vast by comparison although i could live with 20 watts and a backup capable of keeping things going for 5 hours in a power out. I know these mini / micro itx boards are easy to run from a 12v supply (12v/5v and 3.3v reggies) to big utility battery and constant charge takes care of the UPS side of things.

Long term i will read into the USB literature and experiment over time (As my understanding of the script improves and besides, its good to have a challenge).

I was thinking of using an older style camera too and as you suggest they do ignore the usb when in record mode (something i had not considered).
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Offline waterwingz

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Re: USB Download
« Reply #3 on: 02 / April / 2014, 08:39:46 »
Quote from: stagdriver on 02 / April / 2014, 06:57:55
I am thinking in the short term i will make the camera more accessible to remove the sd card and download without altering the camera position. (probably just power control and set to run script automatically on power resume).
Sounds like the easiest solution if that works out for you.

However, this suggestion by reyalp :
Quote from: reyalp on 01 / April / 2014, 21:45:58
you could probably use the usb remote setting to ignore the USB connection in the shooting cycle and just check for USB power periodically in between.
would be trivial to add to whatever intervalometer script that you choose to use.  Post a link to the script you want to use (or attach the script here) and I can make the changes for you.

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I was thinking of using an older style camera too and as you suggest they do ignore the usb when in record mode (something i had not considered).
Not every older Canon P&S will do this.  There might be a list somewhere of this that do but I do not believe that I've seen one.
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Offline Microfunguy

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Re: USB Download
« Reply #4 on: 02 / April / 2014, 09:13:09 »
Quote from: stagdriver on 02 / April / 2014, 06:57:55
I am thinking in the short term i will make the camera more accessible to remove the sd card and download without altering the camera position.

That is what I do with my fourteen A620 timelapse rigs that are currently in operation.
I open the SD card cover (while the script is running !), replace the card and close the cover.
The camera restarts and autoruns the timelapse script.


David
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Offline stagdriver

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Re: USB Download
« Reply #5 on: 02 / April / 2014, 14:10:43 »
Thanks Microfunguy,
so let me get this right. You simply remove your sd card without switching anything off and the chdk copes with this?
Seems like a perfect solution, i will give it a go tomorrow in my workshop.
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Offline stagdriver

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Re: USB Download
« Reply #6 on: 02 / April / 2014, 14:14:13 »
Thanks Waterwingz.
i will be using "Ultimate Intervalometer" of course.

I Appreciate you doing this as it will help me learn more about scripting.
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Offline Microfunguy

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Re: USB Download
« Reply #7 on: 02 / April / 2014, 16:12:16 »
Quote from: stagdriver on 02 / April / 2014, 14:10:43
You simply remove your sd card without switching anything off and the chdk copes with this?

I am actually using SDM but that makes no difference.
This is the simple script that I use and it works perfectly .. of course :-

Code: [Select]
@param i interval in minutes
@default i 5
@param t start hours
@default t 8
@param f finish hours
@default f 16

Start_hour t
End_hour f
time_lapse 0, 30, i, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0

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Offline stagdriver

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Re: USB Download
« Reply #8 on: 03 / April / 2014, 07:36:19 »
tried removing the sd card on A470 and a 550 with external psu and door open (microswitch held closed with matchstick) and both cameras turned fully off immediately when i removed the sd card.
Sure i'm not understanding something here.
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Offline Microfunguy

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Re: USB Download
« Reply #9 on: 03 / April / 2014, 12:41:47 »
Just to be clear, on my A620's the power button is mechanically permanently depressed.
The card door-switch is not overriden so the camera turns off when I open the door.
I replace the card and battery and then close the card door.
The camera boots and autoruns the above script.

David
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