[Alan Anderson]

The pins labeled (-) aren't really "ground", but I'll call them that here.

The voltage between the power and ground pins on a Digital I/O port should be 5 volts. If you're reading 2.5, you probably don't have the Digital Sidecar powered properly. Are all three of its power LEDs lit? Does the large amber Robot Signal Light blink with the expected pattern? Please describe exactly how the Digital Sidecar is connected to power, so we can help you verify that it really is according to the insstructions.

There is no power on the relay pins on the Digital Sidecar. There are two signal pins and one "ground" pin. Unless a relay is being energized, you won't find any voltage present.

Unless you install a servo power jumper on a PWM port, you won't read any voltage there either. With the power jumper in place, you should see 6 volts.

The servo itself doesn't report its position. When you use the getAngle function, what you get is a scaled version of the position the software is telling the servo to go to.