>i2c bus at 3.3V

If you use bit banged I2C then use a separate data in and out pin and you
are set. The data out only needs a shottky diode, the input a
(relatively large) resistor. The clock driver can have just a series
resistor. Most I2C components clamp the I2C pins efficiently to Vcc and
GND and are not bothered by this mode of operation. However, check ;-)

Peter

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