Question

What is the function of the IOREF pin on the Arduino UNO?

(a) To provide a constant 12V DC supply

(b) To provide the voltage corresponding to the standard GPIO working voltage of the board

(c) To take input voltage and set it as a reference for all GPIO operations

(d) To provide ground

The question was asked in semester exam.

The origin of the question is Board Pinout Structure in section Board Specifications and Types of Arduino

Answer 1

Right choice is (b) To provide the voltage corresponding to the standard GPIO working voltage of the board

To explain I would say: The IOREF pin provides the operation voltage reference for the Arduino. Usually on most Arduino Boards that is 5V but on the Diecimila it is 3.3V however. But this pin should not be at any given time connected to a load as power source.