There is a Bi-Directional Shifter made from a pair of 2N7000's and an extra set of pull-ups (for the 3V3 side) that works Very Well, I've used it twice and had excellent results both times NXP10144 I think is the number of the app note from NXP that desccribes the interface. I made one from a pair of C945 transistors and an extra resistor for base current limiting that worked well also, that one I modeled first in MultiSim... before I used it. All worked well bi-directionally.
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