I have begun creating a CHDK trigger cable for the Pixhawk autopilot in my IRIS+ drone.
It will allow me to control a Canon compact camera (IXUS 60 in my case since I had one of those laying around) from the autopilot.
CHDK is the Canon Hack Development Kit which will allow you to do a whole lot more with a Canon compact camera than what the basic knobs and dials will let you do. It also allows for scripts to be run on the camera – LUA (nice) and Basic (yuck) – and enables remote control through the USB port.
The purpose of this trigger cable is to convert the 3.3 V RC PWM signals from the Pixhawk (PWM with pulses from approximately 1000 µs to 2000 µs; read more here if you want) to 5 V pulses (from about 10 to a couple of hundred milliseconds) for the camera.
With the trigger cable complete and the camera mounted on the IRIS+, I can trigger shots from either the RC transmitter or by using pre-programmed actions in auto-missions. Those images can later be stiched together in Photoshop or Microsoft ICE or similar to create a nice high-resolution aerial photo.
While I'm sure this project could be implemented using less sophisticated hardware, I'm using an LPC11U24 microprocessor since that is my weapon of choice for pretty much anything.
I'm trying to make the device as small as possible so I will be using a 7 x 7 mm HVQFN package which will require the PCB to be reflow soldered (we've come a long way since all ICs had to be 0.1" DIL packages). I will also be using a 1 mm pitch JST-SH connector for MCU programming instead of big 0.1" pin headers. Both power and signal input as well as output signal will use Molex SL connectors with locking tabs (which I use everywhere else on my IRIS+).
The resulting images will look this one from a thread on DIY Drones ( A successful APM aerial survey mission):