As succesor of my wonderful Canon A570IS KAP camera (that began to have errors writing jpeg sometimes) I was looking for a wide angle camera preferably with CHDK, and came to the Canon Ixus 870IS (SD880IS):
* 28mm wide angle
* 32 MP/cm² pixel density
* good reviews for photo quality on Dpreview and Cnet
* 205 grams with battery
* it has a working CHDK (at the moment only some functions not needed for KAP are missing)

While the spec's and reviews are positive.
Is it in practice the perfect camera for KAP?
Well: not exactly.

After getting the camera I found some issues with this camera:
1) LCD display eats batteries, however you cannot switch it off on the 870IS: Pressing 'display' button will only toggle between the display between modes with more or less information on the display, but the LCD will stay on. In the manual, you can find that you can assign the print-button for switching the display of. By holding the print button in record mode, the LCD will switch off, but the LCD will switch on automaticly the moment a picture is taken. It is said this is because there is no viewfinder on the camera.

2) For a Video downlink: the camera has no separate connector for video out. There is a propriety video cable delivered by the camera, and when inserted the video output is redirected from the LCD display to the cable.
But the cable connects to the USB port on the camera... the port you like to use for triggering the camera!
The propriety video cable has 6 pins on the narrow side of the mini-usb connector:

while a standard USB has 5 pins on the opposite side (the wider side):

So no way to modify a USB-cable to get video, or even combining it with USB-triggering. Damn.

I really considered bringing the camera back.

However there is rescue:
1) Virtually pushing the print-button with CHDK proved hardly doable in timing and hardly effective if you make a fast sequence of pictures.
However since around january 2009 the following command is available in CHDK: set_backlight 0

As a simple example:

:loop
set_backlight 0
do
a = get_usb_power
set_backlight 0
until a>0
shoot
goto "loop"
The display still will switch on when making a picture, but within a fraction of a second be switched of again (in the next loop waiting for usb), so minimal loss of power.

2) Either a usb-connector for USB-triggering or for video downlink but not combined isn't very nice, so what really idealistic would be needed is a tiny mini usb-connector with: 11 pins...
Well: 11 pin connectors that are almost like mini-usb connectors are available: for the HTC Touch mobile (or G1 android mobile phones), called 'ExtUSB". They ExtUSB is bigger (for example one square corner), and won't fit in a standard sized usb port. Converters are available, e.g. this one.

The wiring of pins proved to be probably not usable for the Canon, so rewiring or microscopic chirurgical modifications could be needed.
I was happily astonished when I found this little gem: a 11-pin mini usb connector with breakout.
I ordered it via Coolcomponents.
The connector is too large for the Canon usb-port, but it comes in 3 separate pieces, it is easy to handle with. I removed the metal chassis, and cut some edges of the plastic, and the connector fitted.

The layout of the breakout:
6 9 11 5
O O O O
7 8 10 4
O O O O
1 2 3
O O O

Pins 1 to 5 are the standard USB pins:
1: USB VCC +5v
2: USB Data -
3: USB Data +
4: N / C
5: USB GND

After some research on the proprietary cable, and trial on the breakout connector I found out that Canon uses:
6: Ground
7: Short with pin 6 for enabling video output
8:
9: Audio
10: Video
11:
12: Chassis Ground (GND)

It works! The camera can be triggered with CamRemote via pin 1 and 5, and was able to get video output with 6&7 as ground and [edit]10 (thanx to David Sykes for reading carefully)[/edit] as video.
Test setup for video output: .
Using this connector is another solution for the LCD off issue.

So, with some effort, the Canon can be a good KAP camera after all. Above story will hold for the Ixus860IS/SD870IS also.

And for a last issue:
3) 28mm wide angle made a rig leg visible in the image! Duhhh... ;-)

Well, I do like legs on the rig: for safety with a hard landing, for keeping the camera getting dirty with a soft landing, and practical: you can confortably put the rig on the ground (or at home on a table) while doing other things.
With some physical rearrangements, the one leg isn't in the image anymore, so issue solved. I could also easily cut the legs with scissors to make them a bit shorter because (they are made from plastic)

That's a good find locating that connector. The common name for it is "HTC ExtUSB" due to its use in HTC phones.

Sparkfun has both the breakout connector mentioned above as well as the bare connector without the circuit board on the end. It turns out that if you pull the plastic part out of the connector and file down the shoulders of the connector, you can push it into a standard USB Mini-B connector shell.



Here's a picture showing the pinouts for those not using the breakout board. This is looking into the plug on the end of the cable. I found that Chassis Ground and USB Ground are the same and Pin 8 is tied to Pin 7 on a SD940.



Another interesting thing is that Canon is putting this connector on the back of some of their smaller cameras rather than on the side. This might be a more KAP-friendly way for cables to exit the camera.