I am building a project that includes an analog Input and several digital Inputs and Outputs. All of them connect to ground in some way. Do I need to worry about voltage, coming from the digital outputs, going to ground, and effecting readings on the analog input? If so, how do I deal with this?
The arduino has build in pull up resistors, it is not a residue voltage coming from ground more than a "not 100% 0 volt" resistor.
Even though there is built in pull-up resistors one can add additional resistance to the arduino to make sure it will not show a false positive.
From what i have learned, you cannot experience voltage comming from ground (if everything is properly wired), if you want to make sure. Place a diod in the direction of the power flow, to prevent this.