Don't forget that there is a simple way to drive from a PIC at 5V to
a 3.3V peripheral. With PORT bit always low, just use the TRIS bit to
drive the output low, and use a pullup to 3.3V to set the level.

SOME 3.3V peripherals have input diode clamps that will clamp a 5V level
to 3.3V as long as a series resistor is used. I find that 470 to 1000
ohms always works. But... be sure to verify that the device HAS clamp
diodes heavy enough to handle the current (5V-3.3V/470) [362uA for 470
ohm] when the 5V is at a ONE state.

The other direction usually takes care of itself, if the impedance of
the signal is low enough.

--Bob
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                Bob Axtell
        PIC Hardware & Firmware Dev
          http://beam.to/baxtell
              1-520-219-2363

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