merge libmaple docs ("leaflabs-docs") into ./docs

In the past, libample documentation was forked out of this repository
because the documentation had increased in scope. For the librambutan,
and the rambutan project in general, we will try to keep documentation
closer to the source code, so the librambutan-specific documentation
should live here. Other sections of leaflabs-docs will be culled in a
following commit.

This merge attempts to maintain history by using a subtree strategy.
Followed directions at:

    http://nuclearsquid.com/writings/subtree-merging-and-you/

Full history for files should be accessible using the "--follow" flag to
git log, eg:

    git log --follow docs/source/adc.rst

It should be possible to pull patches from leaflabs-docs with:

    git pull -s subtree leaflabs-docs master

... at least until the docs in this repository diverge significantly.

1 files changed, 61 insertions, 0 deletions

diff --git a/docs/source/lang/api/pwmwrite.rst b/docs/source/lang/api/pwmwrite.rst
new file mode 100644
index 0000000..5cc112e
--- /dev/null
+++ b/docs/source/lang/api/pwmwrite.rst
@@ -0,0 +1,61 @@
+.. highlight:: cpp
+
+.. _lang-pwmwrite:
+
+pwmWrite()
+==========
+
+Writes a :ref:`PWM wave <pwm>` to a pin.  You can use this to make an
+LED get brighter or dimmer, control a servomotor, etc. After a call to
+pwmWrite(), the pin will output a steady square wave with the given
+duty cycle.  You can change the duty cycle later by calling pwmWrite()
+again with the same pin and a different duty.
+
+The pins which support PWM have ``PWM`` listed underneath their number
+on your board's silkscreen.  These pin numbers are available to your
+program in the :ref:`boardPWMPins <lang-board-values-pwm-pins>`
+board-specific array.  The number of pins which are capable of PWM on
+your board is given by the ``BOARD_NR_PWM_PINS`` constant.  These
+values are documented for each board in the :ref:`Board Hardware
+Documentation <index-boards>` pages.
+
+The Arduino function :ref:`analogWrite() <lang-analogwrite>` is an
+alias for ``pwmWrite()``, but it is badly named, and its use is
+discouraged.
+
+.. contents:: Contents
+   :local:
+
+Library Documentation
+---------------------
+
+.. doxygenfunction:: pwmWrite
+
+Example
+-------
+
+Sets the output to the LED proportional to the value read from the
+potentiometer::
+
+    int analogPin = 3;    // potentiometer connected to analog pin 3
+
+    void setup() {
+      pinMode(BOARD_LED_PIN, OUTPUT);   // sets the LED pin as output
+
+      pinMode(analogPin, INPUT_ANALOG); // sets the potentiometer pin as
+                                        // analog input
+    }
+
+    void loop() {
+      int val = analogRead(analogPin);        // read the input pin
+
+      pwmWrite(BOARD_LED_PIN, val * 16);  // analogRead values go from 0
+                                          // to 4095, pwmWrite values
+                                          // from 0 to 65535, so scale roughly
+    }
+
+See Also
+--------
+
+- :ref:`Maple PWM tutorial <pwm>`
+- :ref:`boardPWMPins <lang-board-values-pwm-pins>`