As part of my Projekt365 I realized that I was going to need to buy/make some equipment. The first piece of equipment that will be made is going to be a shutter release for the Canon Digital Rebel (300D). I’m not going to go into great detail of how the Canon shutter release works as it is well documented. However, I will go into detail about the design of my shutter release.
My shutter release is going to be digitally controlled. I have selected the AVR Butterfly Evaluation Kit (link) as the basis for the controller. This evaluation kit provides all of the necessary microcontroller support circuitry as well as a nice LCD screen, and is quite extensible in addition to being a handy form factor. It also provides a nice serial interface for programming so that there is a low barrier to entry for non electrical engineers. 
I will be designing a board that nestles underneath the butterfly board to provide my application specific circuitry. This will be a quite simple board comprised of a couple of optocouplers, a 2.5mm stereo headphone jack and inter-board connectors.
The real guts of the whole device will be the firmware running on the Atmel ATmega169 microcontroller. Currently I’m planning to support the following modes of operation:
- One-shot manual (don’t know why I need a remote to do this, could just press the button)
- One-shot delay (to allow me to run back into the frame to do self-photos)
- One-shot exposure timer (for long exposures)
- One-shot exposure timer with delay (combines the previous two operating modes)
- Time lapse (trigger an arbitrary number of frames at an arbitrary frequency with an arbitrary exposure length)
- Light meter (the butterfly has a light dependent resistor on the board!)
The AVR Butterfly has a handy 32KHz crystal on board for driving a real-time clock making all of these operations really easy. The control will be implemented as a state machine to setup the timer components and then fall back to sleep. More documentation will follow as I start whacking at code. I will ultimately open source the hardware and software design once I finish it. Look for more to come!