holmes4:
From the datasheet Section 28.2, for an UNO running at 5V a digital input will read high at a voltage of just 0.6V. Is this correct?.Mark
No, the spec is saying that the minimum input pin voltage needed to be detected as a HIGH is .6 X Vcc (60% of the actual Vcc voltage being used). So for a 5 volt arduino board the minimum input pin voltage guaranteed to be detected as a HIGH is +3.0 vdc.
For a 3.3vdc powered board the value would be 1.98vdc.
Lefty
Ah, TC beat me to it. 