Newbie here...go easy on me....LOL. I have been working on a SD card shield that will work between the MEGA ADK and the DUE (5v vs 3.3v IOREF) my question is this......if I connect my reference pin on the level translator to 3.3 the Due works but if I connect it to the IOREF it will not.....the MEGA work fine........I did a continuity reading between the 3.3v and the IOREF pin on the Due and they are connected....what gives ?

Thank you, David

I think the IOREF will be connected to either 5V or 3.3 depending on what the microcontroller needs. On my shield, I had some 3.3V RS485 drivers and used a 74LVC07A powered with 3.3V to go between the 5V levels and 3.3V. Its input is tolerating of 5V even when powered with 3.3V. The open drain output can be pulled to IOREF (3.3 or 5 V) with a pullup resistor. There are many other ways to do this, but so far I like this. My shield should work with the new Arduino Zero (3.3V) when it is out, but will have to see.