Simply connect the wire that you want to measure to a digital pin, and the grounds together. The you can do a digital.read. You may need to pull it low when the line is low but that depends on the source of the signal you are trying to measure?
Simply connect the wire that you want to measure to a digital pin, and the grounds together. The you can do a digital.read. You may need to pull it low when the line is low but that depends on the source of the signal you are trying to measure?