analogReference()

Abstract

The analogReferece() sets the reference voltage for analog input. It just sets a global variable.

Source Code

The analogReference() is defined in hardware/arduino/avr/cores/arduino/wiring_analog.c as below.

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uint8_t analog_reference = DEFAULT;

void analogReference(uint8_t mode)
{
        // can't actually set the register here because the default setting
        // will connect AVCC and the AREF pin, which would cause a short if
        // there's something connected to AREF.
        analog_reference = mode;
}

The input is mode and its type is uint8_t. The mode can be one of ‘DEFAULT’, ‘INTERNAL’ or ‘EXTERNAL’.

This function stores the mode into the global variable named analog_reference. The analog_reference is used in analogRead().

Version

Arduino AVR Boards 1.8.6

License

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/*
  Copyright (c) 2016 garretlab.
  Added source code explanation by garretlab.
*/

/*
  wiring_analog.c - analog input and output
  Part of Arduino - http://www.arduino.cc/

  Copyright (c) 2005-2006 David A. Mellis

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General
  Public License along with this library; if not, write to the
  Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  Boston, MA  02111-1307  USA

  Modified 28 September 2010 by Mark Sproul
*/

Last Update

July 31, 2025