4V - 5V signal on Digital Input

[billbo911]

Originally Posted by tdlrali

Thanks guys, I'll look into those options. The only reason we don't want to use analogs is because we're really just looking for on vs. off, and the additional sampling required for using an analog input is overkill.

It may be overkill, but if the custom circuit's output does not operate such that it meets the designed parameters of the RC, then you need to adjust your approach.
An analog comparison will only take a couple lines of code.

{
char a;
{
if (Get_analog_01() <= 800)
{
a = 0;
}
else
{
a = 1;
}
}