I'm assuming that the digitalRead() function operates at standard TTL levels? "low" when between 0 V and 0.8 V with respect to the ground terminal, and "high" when between 2.2 V and 5 V"
Or does it operate at some other voltage levels?
Thanks
-Dan
digitalRead() is checking the pin's input register, which is loaded based on the pin's voltage.
The value of Vlow and Vhigh depend on the chip's Vcc. For details, you can look at the ATmega's DC Characteristics in the datasheet for the values (show below).
If Vcc = 2.4v to 5.5v then:
Vlow = -0.5v to 0.3Vcc
Vhigh = .6Vcc to Vcc+0.5
So if Vcc = 5v, then
Vlow is -0.5v to 1.5v
Vhigh is 3v to 5.5v