OK, so I got my first Arduino (RobotDyn CH340/A 2650) several months ago, and I've been playing with it ... experimenting .... learning ... tons of Googling ... Ive even successfully used a few shields ... but I'm struggling with something that I feel should be very easy to grasp and I've decided to post my dilemma here.
I seem to be struggling with inputs and accuracy in reading voltages. You see, when I set a pin as an input because I want to read some voltage (between 0 and 5 volts of course), the behavior of the Arduino does not seem to be consistent from one pin to the next, and I want to start a project that would require some consistency in this thing. I'm starting to wonder if this unit is faulty.
When you set an analog pin such as A10 as an input, then start reading the pin value without any voltage applied to it, is it normal to get readings in the 500 range? When I take the pin to ground, SOMETIMES it goes to zero (depending on the pin), and sometimes it makes no change at all. Then when I apply a small voltage to it, sometimes it changes, sometimes it doesn't and again it seems to be depend on the pin im using (usually between A10 and A15).
Second question: Ive noticed that when I declare an int to something like A8, it actually comes out as 62 when I print it to serial. So that got me wondering about the literal pinouts etc., and in my searching, I looked at this link for my unit, but according to that page, pin 62 is ground ... so what gives?
Is there a way to test this thing and the inputs to make sure they are functioning properly? Some kind of uniform thing I can do say with a AA batter or something that I can apply to certain pins and get a known value etc.?