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Remote capture trigger via av connection

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Remote capture trigger via av connection
« on: 23 / April / 2010, 17:17:36 »
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Hello
I'm new to all this, I've just upgraded my firmware to CHDK on an IXUS 40 to get remote capture (using an old camera, don't want to destroy my newer ones) - with which I've succeeded (thank you all) and then exceeded.  The remote capture described in the help uses an USB cable modified so I got that working but then thought I want this controlled from the PC so I've hooked the hacked USB cable to the parallel port and using some port controller software succeeded in triggering capture.  Once I have things simplified and properly developed I'll post it up so others can benefit too.  Basically you have to connect the red 5V line to LPT port (output) pin, any from 2 to 9 and the black ground to (ground) any pin 18-25. Whichever output pin (red cable) was used (connected) is that pin which has to be switched high sending 5V down the cable.  To trigger an image capture it has to be a sequence of high (focus and evaluation) then low-high-low in quick succession - the second high triggers capture. It seems impossible to use the PC USB port to acheive remote capture but I will keep looking (for a bit). It may also be possible from a COM port, but I've not looked into it.

But this is not enough.  I want to transfer the images over USB (there's no other way) after capture because I want to geotag and post process and cameras only have one USB port, so I wanted to ask if it would be possible to trigger capture using the AV port of the camera? Do you think this might be possible? Many thanks for the great work already done I'm amazed


« Last Edit: 24 / April / 2010, 15:57:31 by ceegee »

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Offline reyalp

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Re: Remote capture trigger via av connection
« Reply #1 on: 24 / April / 2010, 21:01:38 »
It seems impossible to use the PC USB port to acheive remote capture but I will keep looking (for a bit). It may also be possible from a COM port, but I've not looked into it.
The experimental PTP interface will let you do this on supported cameras. See http://chdk.setepontos.com/index.php/topic,4338.0.html
AFAIK ixus40 is not currently supported, but if you are a programmer, adding support shouldn't be too difficult. (although be warned that ixus40 is one of the very old vxworks cameras that is a bit different from most)
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But this is not enough.  I want to transfer the images over USB (there's no other way)
Eyefi or similar is another way. http://www.eye.fi/
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after capture because I want to geotag and post process and cameras only have one USB port, so I wanted to ask if it would be possible to trigger capture using the AV port of the camera? Do you think this might be possible?
I was going to say that the AV plug is output only, but this is not strictly true. The screen turns off when the AV is plugged in. In theory, CHDK can detect this and use it as an input much like USB, but it currently doesn't. Again not difficult to implement if you are a programmer.

On cameras like the ixus40, which have a separate 1/8" AV plug, this detection is (as far as we know, not all cameras have been tested) done by a mechanical switch. We know this because as a toothpick can be used to trigger it. I'm not sure what the ones that share AV with the USB plug do.

With this, and other switches, you could rig up electro-mechanical actuators, or open up the camera and wire directly to it.

edit:
BTW, the ixus40 manual says "The interface cable and AV cable cannot be connected simultaneously", so the behavior might be undefined.
« Last Edit: 24 / April / 2010, 21:03:57 by reyalp »
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