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+.. highlight:: cpp
+
+.. _arduino-analogread:
+
+analogRead()
+============
+
+
+Signature
+---------
+
+``int analogRead(int pin);``
+
+
+Description
+-----------
+
+Reads the value from the specified analog pin.  The Maple board
+contains a 16-channel, 12-bit analog to digital converter.  This means
+that it will map input voltages between 0 and 3.3 volts into integer
+values between 0 and 4095.  This yields a resolution between readings
+of 3.3V / 4096 units, or 0.8 millivolts.  However, a number of factors
+interfere with getting full accuracy and precision.  For more
+information, see :ref:`adc`.
+
+Before calling analogRead() on a pin, that pin must first be
+configured for analog input, using :ref:`arduino-pinMode`.
+
+The input range and resolution can be changed using
+:ref:`arduino-analogReference`.
+
+It takes about 0.8 microseconds (.0000008 seconds) to read an analog
+input, so the maximum sample rate using this function is approximately
+1.3 million samples per second [#fsamp]_.
+
+
+Parameters
+----------
+
+**pin**
+
+  The number of the analog input pin to read from.  Header pins on the
+  Maple with ADC functionality (marked as "AIN" on the silkscreen)
+  are:
+
+    0, 1, 2, 3, 10, 11, 12, 13, 15, 16, 17, 18, 19, 20, 27, 28
+
+  Note that pins 3, 27, and 28 are not marked AIN on the silkscreen
+  for Maple revisions through Rev 5, however, they **do work** as
+  analog input pins.
+
+Returns
+-------
+
+Converted input voltage as an ``int``, with value 0 to 4095, inclusive.
+
+
+Note
+----
+
+If the analog input pin is not connected to anything, the value
+returned by analogRead() will fluctuate based on a number of factors
+(e.g. the values of the other analog inputs, how close your hand is to
+the board, etc.).
+
+
+Example
+-------
+
+ ::
+
+     
+    int analogPin = 3;     // potentiometer wiper (middle terminal) connected to analog pin 3
+                           // outside leads to ground and +3.3V
+    int val = 0;           // variable to store the value read
+    
+    void setup() {
+      pinMode(analogPin, INPUT_ANALOG);
+      SerialUSB.begin();
+    }
+    
+    void loop() {
+      val = analogRead(analogPin);    // read the input pin
+      SerialUSB.println(val);         // debug value
+    }
+
+
+Arduino Compatibility Note
+--------------------------
+
+The Arduino board contains a 6 channel (8 channels on the Mini and
+Nano, 16 on the Mega), 10-bit analog to digital converter. This means
+that it will map input voltages between 0 and 5 volts into integer
+values between 0 and 1023. This yields a resolution between readings
+of: 5 volts / 1024 units or, .0049 volts (4.9 mV) per unit.  On the
+Arduino, the input range and resolution can be changed using their
+implementation of `analogReference()
+<http://arduino.cc/en/Reference/AnalogReference>`_\ .
+
+On the Arduino, it takes about 100 microseconds (0.0001 s) to read an
+analog input, so the maximum reading rate is about 10,000 times a
+second.
+
+
+See also
+--------
+
+- :ref:`ADC note <adc>`
+- :ref:`analogReference <arduino-analogreference>`
+- `(Arduino) Tutorial: Analog Input Pins <http://arduino.cc/en/Tutorial/AnalogInputPins>`_
+
+
+.. rubric:: Footnotes
+
+.. [#fsamp] This is based on the current configuration of a 55.5 cycle
+   sample time, at 72 MHz. However, the minimum sample time *possible*
+   is 1.5 cycles, leading to a theoretical maximum of approximately 48
+   million samples per second (of course, doing anything with the
+   readings also consumes cycles, so this maximum can't be reached in
+   practice).
+
+   See the `STM32 Reference Manual <full-manual>`_, §§11.12.4--5
+   (pp. 225--226), for more information on the low-level bit twiddling
+   currently necessary to change the sample time.  For examples of how
+   the ADCs are configured in libmaple, see `adc.h
+   <http://github.com/leaflabs/libmaple/blob/master/libmaple/adc.h>`_
+   and `adc.c
+   <http://github.com/leaflabs/libmaple/blob/master/libmaple/adc.c>`_\
+   .  Be aware that changing the sample time has important
+   consequences related to the impedance of the device connected to
+   the input pin.  If you want to make changes, as a minimum, you
+   should first read ST's application notes on `ADC modes
+   <stm32-adc-modes>`_ and `ADC oversampling
+   <stm32-adc-oversampling>`_.