... Actually it seems to have solved my problem, though maybe not in the intended way - it seems as though plugging and unplugging the cable to the phone while CHDK is in remote mode actually has the same effect as the power pack option you suggested...
On my Nexus 7 I can connect a 4-port USB-2 Hub via a OTG adapter a USB mouse and a Portable USB-2 keyboard.
The Nexus 7 then powers the USB-2 Hub via the OTG adapter.
So there are still two free USB-2 ports for use with CHDK cameras.
My 4-Port USB Hub has an small external power connector which could be modified, internally, as per Option #1.
Would be to internally modify the, spare ports, USB-2 Hub. If you have the necessary skills.
Would be to use a external CHDK USB-2 switched cable on a spare hub port.
Would be to use Canons Camera Connect via a Wi-Fi capable canon camera, that supports remote shooting.
you can use the mouse to click on the apps shoot button.
Unfortunately Canons Camera Connect (CCC) doesn't currently support a script interface.
It might be possible to create a very simple app that's only function is to press the (CCC) apps shoot button.
Could be to use the TriggerTrap (TT) Mobile app, that supports a open source (OS) interface for some DSLR Canon Cameras.
It works via, a very short audio output, on the headphone jack. see herehttp://www.triggertrap.com/how-to/use-a-cable-releasehttps://en.wikipedia.org/wiki/Triggertrap
The original open source, passive, interface that TriggerTrap provided is very basic. i.e. Version 1
I think that by adding a few more simple electronic component's it could be made to work well with CHDK.
A Quote from TT https://triggertrap.reamaze.com/kb/triggertrap-mobile-4/what-s-the-difference-between-the-triggertrap-mobile-dongle-1-and-2
"...The differences are that version 3 is a lot more sensitive.
This makes it compatible with a lot of devices that previously weren't compatible due to volume issues.
The sensitivity will also make it a little faster on iOS devices..." (BUT Version 3 is now a Closed Source version.)http://www.triggertrap.com/license/http://www.diyphotography.net/building-diy-trigger-trap/
More Link's for the original OS TriggerTrap Interface To Do.
Edit #1 also see an old post here
Option #5:- Remote control Android (Reply #21 but via a TT Audio Pulse)https://chdk.setepontos.com/index.php?topic=6823.msg72835#msg72835
« on: 06 / September / 2011