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+.. highlight:: cpp
+
+.. _lang-analogwrite:
+
+analogWrite()
+=============
+
+.. note::
+
+   On the Maple, calling analogWrite() is the same as calling
+   :ref:`lang-pwmwrite`\ ; see that function's documentation for more
+   information.
+
+   This is because PWM is not true analog output (i.e., is not the
+   output of a `DAC
+   <http://en.wikipedia.org/wiki/Digital-to-analog_converter>`_\ ), so
+   the function is badly named.  For instance, **analogWrite() has
+   absolutely nothing to do with** :ref:`lang-analogread`\ , which is
+   potentially confusing.
+
+   The alias of analogWrite() to pwmWrite() is provided (sigh) for the
+   sake of compatibility with Arduino, but we recommend using
+   :ref:`lang-pwmwrite` when writing new software, for clarity.
+
+.. contents:: Contents
+   :local:
+
+Arduino Compatibility
+---------------------
+
+There are a few important differences between Arduino's `analogWrite()
+<http://arduino.cc/en/Reference/AnalogWrite>`_ and Maple's
+:ref:`lang-pwmwrite` that you should keep in mind.  In each case, we
+have some recommendations you can use to help converting from Arduino
+to Maple.
+
+Difference 1: Duty cycle range is different
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The first and most important difference is that the largest possible
+value for the duty cycle is much bigger on the Maple.  Using Arduino's
+analogWrite(), the duty cycle ranges between 0--255 (always off --
+always on)\ [#fbytemax]_\ .  Using Maple's pwmWrite(), the duty cycle
+ranges from 0--65,535 by default\ [#fuint16max]_\ .
+
+This is a good thing!  The greater range of values on the Maple gives
+you much more precise control over the duty cycle of your PWM output.
+
+If you're porting code from the Arduino and want a quick-and-dirty
+fix, one solution is to :ref:`map <lang-map>` the argument to
+analogWrite into the right range::
+
+    // Arduino code:
+    analogWrite(pin, duty);
+
+    // Becomes Maple code:
+    analogWrite(pin, map(duty, 0, 255, 0, 65535));
+
+This will convert values in the range 0-255 to values in the range
+0--65,635, which is the correct default range for all of the timers
+which control PWM output.  See the :ref:`timers reference <timers>`
+for more information.
+
+Another fix is to consult the :ref:`pin mapping mega table
+<pin-mapping-mega table>` to find the timer which controls PWM on the
+pin you're using, then set that Timer's overflow to 255.  Subsequent
+calls to analogWrite() should work as on the Arduino (with the same
+loss of precision).  Note, however, that that affects the overflow for
+the **entire timer**, so other code relying on that timer (such as any
+:ref:`interrupts <lang-attachinterrupt>` the timer controls) will
+likely need to be modified as well.
+
+Difference 2: You must use pinMode() to set up PWM
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The second difference is that on the Maple, you **must** set up the pin
+for PWM output using :ref:`lang-pinmode`\ , with argument ``PWM``.
+This should just be one extra line of code in your
+:ref:`lang-setup` function.  Example::
+
+    void setup() {
+        // set up pin 9 for PWM
+        pinMode(9, PWM);
+    }
+
+This also means that you can't later call :ref:`lang-digitalread`
+or :ref:`lang-digitalwrite` on that pin (unless some time in
+between, you use pinMode() to reconfigure that pin for ``INPUT`` or
+``OUTPUT``; see the :ref:`lang-pinmode` page for more information).
+
+Difference 3: No PWM on pin 10
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+On the Maple, the pins which support PWM are: 0, 1, 2, 3, 5, 6, 7, 8,
+9, 11, 12, and 14, or twelve pins in total.  That is at least as
+*many* PWM pins as any Arduino board, but there are differences in
+*which* pins support it.
+
+* On **most Arduino boards** (those with the ATmega168 or ATmega328;
+  this includes the **Arduino Uno**), this function works on pins 3,
+  5, 6, 9, 10, and 11, or six pins total.  Note that these boards
+  support PWM on pin 10, while Maple does not.
+
+* On the **Arduino Mega**, PWM works on pins 2 through 13, or twelve pins
+  total.  Note that this board supports PWM on pins 4, 10, and 13,
+  while the Maple does not.  Maple supports PWM on pins 0, 1, and 14,
+  which the Mega does not, making the total number of pins supporting
+  PWM equal on these boards.
+
+* **Older Arduino boards** with an ATmega8 only support analogWrite() on
+  pins 9, 10, and 11.  Maple does not support PWM on pin 10.
+
+In all cases, Arduino boards support PWM on pin 10, unlike Maple.  We
+did our best to make PWM as pin-compatible as possible; however,
+circuit layout constraints prevented us from achieving perfect
+compatibility.
+
+The "safest" pins to use for PWM output are pins 9 and 11.  These pins
+work on any Arduino board and on Maple.  The "safe" pins, which work
+on most recent Arduino boards, the Arduino Mega and the Maple, are
+pins 3, 5, 6, 9, and 11.  Thus, if you want your project to be as
+portable as possible between Maple and Arduino, we recommend using the
+"safest" pins first, then the "safe" pins, as necessary.
+
+Difference 4: PWM frequency
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The frequency of the PWM signal (i.e., the frequency of a complete
+on/off cycle) on the Arduino is approximately 490 Hz.
+
+On the Maple, the frequency is configurable, defaulting to about 1100
+Hz, or 1.1 KHz.  This is because the PWM frequency is the frequency of
+the timer which controls PWM output on the particular pin (\
+:ref:`the PWM tutorial has the details <pwm>`\ ).
+
+If your application absolutely requires Arduino's PWM frequency (it
+probably doesn't), then the steps are:
+
+1. Figure out which timer controls PWM output on your pin (\ :ref:`this table <pwm-timer-table>` is your friend here).  Let's say it's ``Timern``\ , where ``n`` is some number 1, 2, 3, or 4.
+
+2. Call ``Timern.setPeriod(2041)``\ .  This will set the timer's period to approximately 2041 microseconds, which is a frequency of approximately 490 Hz.
+
+Be aware that this will change the period for the **entire timer**\ ,
+and will affect anything else in your program that depends on that
+timer.  One example is :ref:`interrupts <timers-attachinterrupt>`\ .
+You've been :ref:`warned <timers-pwm-conflicts>`\ .
+
+See also
+--------
+
+-  :ref:`Maple PWM tutorial <pwm>`
+
+.. rubric:: Footnotes
+
+.. [#fbytemax] This is because the value for the duty cycle on Arduino
+   must fit in 1 byte of memory, and an unsigned (i.e., nonnegative)
+   integer with size 1 byte can hold the values between 0 and 255.
+
+.. [#fuint16max] This is because the value for the duty cycle on the
+   Maple uses 2 bytes of memory, and an unsigned (i.e., nonnegative)
+   integer with size 2 bytes can hold the values between 0 and 65,535.
+
+
+.. include:: cc-attribution.txt