Hello, just joined but also need to control lens for focus stepping via external sw, so far
pin 1 no contact
pin 2 gnd largest contact area, <1R to battery longest contact
pin3 5V supply
pin4 comms slow rising edge comms when shutter half pressed
pin5 comms data when menu pressed
pin6 clock bursting
pin 7 Gnd <1R to p2
i plan to use the eos SW for my 450D to step focus and analyse the comms to the lens to isolate the focus stepp commands. clock on pin 5 is 78KHz, possibly I2c but i only had 20 mins. good news is its all slow and within pic capability. more to follow.