Hi when I code digitalWrite(inputPin, HIGH) is this just assigning a value of 1 to my inputPin or is it actually applying a voltage near 5V to that pin?
Does anyone know where I can find a diagram of this internal resistor?
The statement digitalWrite(inputPin, HIGH) without context of what the last mode control was (or if the pin is still at the reset/power-up default input mode). The variable inputPin is just a number and by itself doesn't set the pin mode to either input or output mode, it's just used to address the desired pin.
Anyway, if the pin is in fact in input mode, then the digitalWrite(inputPin, HIGH) statement will enable the internal pull-up resistor so the pin will measure a +5vdc at the pin connection, however it does not have the output current capacity of a output pin, just a 40k or so series resistor wired to +5vdc. If the pins mode was set to output mode prior, then the statement digitalWrite(inputPin, HIGH) will set the output to +5vdc and be able to source current up to the rated maximum value.
Figure 14.2 of the AVR mega328 datasheet (version Rev. 8271D–AVR–05/11) shows the I/O pin configuration and an explanation of how the I/O pins work.
Does that help?