I am using a home made time lapse panning head which is constructed around a microcontroller (arduino) and a stepper motor. Thanks to the brilliant work of several forum members (fudgey, fbonomi, outslider, ...) I am getting some reasonable results (from an engineering standpoint if not a artistic one) using a bracketed variable Tv script. Unfortunately at the moment my frame rate is quite limited. I have to be careful to give the camera time to finish the bracketed sequence before the arduino commences the next move, shoot sequence. Ideally I would like the camera to be able to tell the microcontroller that the script has finished.
I can think of a few ugly solutions, for example using an ldr to detect that a viewfinder led has been switched on. However, is there anything else I could do? Perhaps by monitoring pins on the usb port?