Yet another arduino-based camera trigger, posted from [tObY!].
Some time ago I bought a RICOH GR III camera. Since I didn’t want to pay the amount for the CA-1 remote, I did a little research how this thing works. Soon I came up with Muttyan’s home page. This gives a detailed description of the CA-1′s internals and how it works. Good job, there you’ll find everything you need!
Basically a button half press, a full press and a release are signaled with three different patterns to the camera via its USB connection. No “real” USB protocol is used, just pulsing the USB +5V supply line. Emulating these pulses is an easy job with an Arduino board, so I did a quick proof of concept.