I have a canon a520 doing time lapse long term - its been running for 6 months taking one pic every 5 minutes. I'm hoping someone with some experience with chdk can explain how chdk addresses these issues -
1) Does chdk support PTP (Picture Transport Protocol) or something similar?
No. CHDK doesn't, but your camera probably does if it has a USB port. Canon's software isn't the only thing out there that can download images from these cameras. I believe in future, CHDK will be able to switch between rec and play modes from scripts...if you are a programmer, you can probably help speed up cooking that feature up.
2) Does chdk keep accurate time? (something i have trouble with in the stock firmware) Is there a way to update the time over USB?
CHDK doesn't keep time, it relies on the camera to do that. Unless the Canon SDKs specify a way to adjust camera clock, there isn't an official way. But if I'm not mistaken, CHDK could very well be programmed to set time (even via USB) one way or another if this feature seems necessary. You can do a feature request...
does anyone know how to remotely power on the canon a520? the button on the top must be pressed and released once power is supplied. i'd like a way around this.
Some camera models can be powered on by plugging in the USB cable (the other end must be connected to a voltage source like a computer). http://chdk.wikia.com/wiki/CameraFeatures
doesn't list the a520 so I have no clue if yours is one of these. I'm not sure if they have to be in play mode for that (my a570is doesn't power on from USB). I don't know of any other way other than pressing the button (or rewiring the button, of course).