As the title suggests, make a shield for the Duo so you can switch level shifting on/off (preferably on a pin by pin or port by port basis) for most/all the data pins. I have sooo much stuff that is 5V and the Mega/UNO are not big/fast enough for some projects I want to do but external level shifter…

Arduino Due level shifter shield to make pins 5V tolerant

graynomad June 25, 2013, 6:34am 6

Not sure if this is it, but it's in the ball park

Rob