thanks for the details about the level shifter.
I can't exchange any circuits: All electronics are in one project box, the lens mounts/adapters are going to be connected by cable with a 12 pin Hirose connector and I can't fit a levleshifter inside those mounts/adapters or connectors. I'm using a m4/3 camera (BMCC) and different adapters for FourThirds (3.0V), Nikon (5V) and Cannon (5.5V) lenses and want to remote control those lenses (focus, aperture, read focus distance,...). So, what about...
1) Using the level shifter with HV < LV (3.0V < 3.3V). As I understand it, this should be fine, as long as the difference is small (0.3V). Will the level shifter be fast enough for 500 kHz SPI in this configuration? Any other bad side effects?
2) Is it possible to mount two level shifters back-to-back, so that one is HV->LV and the other LV->HV and connect both to the same wires?
3) Is there a level shifter on the market that has no "direction"?
4) The 3.0V lenses are FourThirds format... I might get away with 3.3V instead of 3.0V, but that would be the worst option, as those are really expensive lenses and I don't want to fry them.