I am attempting to use a second Arduino to read the output of a first Arduino. To do this I have constructed an external pull-up circuit as shown below.
I have found on one input I am able to get a readable voltage range of 4.1 to 1 V between high and low (sufficient to get a reading) whereas from a second output pin on the Arduino I am only seeing a 0.3 V change between high and low using an identical pull-up circuit.
Any suggestions as to the possible cause of this behaviours.
Apologies if the description is insufficient,go easy on me I'm only a mechanical engineer :)