I'm trying to interface an ADC chip to a 5V Arduino. The data sheet for the ADC says driving inputs above 3.3V has a total limit of 50 ma. So I added 1K resistors on the digital pins (5V/1K * 8 = 40 ma). The Sparkfun 3.3V example shows pullups used sometimes too. Do I need the pullups to drive a logic high from the ADC to the '328 ? Sinking current is maybe different than sourcing it ?