1 files changed, 65 insertions, 1 deletions
diff --git a/docs/source/spi.rst b/docs/source/spi.rst
index 8518f3c..3c29b79 100644
--- a/docs/source/spi.rst
+++ b/docs/source/spi.rst
@@ -4,4 +4,68 @@
  SPI
 =====
 
-Stub.
+The Maple has two SPI ports. The first has NSS on D10, MOSI on D11,
+MISO on D12, and SCK on D13. The second has NSS on D31, SCK on D32,
+MISO on D33, and MOSI on D34.
+
+.. _spi-speeds:
+
+Each port can be configured at one of the following speeds:
+
+* ``SPI_18MHZ``: 18 MHz
+* ``SPI_9MHZ``: 9 MHz
+* ``SPI_4_5MHZ``: 4.5 MHz
+* ``SPI_2_25MHZ``: 2.25 MHz
+* ``SPI_1_125MHZ``: 1.124 MHz
+* ``SPI_562_500KHZ``: 562.500 KHz
+* ``SPI_281_250KHZ``: 281.250 KHz
+* ``SPI_140_625KHZ``: 140.625 KHz
+
+.. contents:: Contents
+   :local:
+
+Function Reference
+------------------
+
+``HardwareSPI Spi(number);``
+
+    This declaration must be included at the start of any sketch or
+    program that uses the SPI interface. The argument number is either
+    1 or 2 and specifies which port to use.
+
+``Spi.begin(freq, endianness, mode)``
+
+    ``begin`` is usually called in `setup()`_ to configure the
+    baudrate of the given SPI port and to set up the header pins
+    appropriately. ``freq`` is one of the set listed :ref:`above
+    <spi-speeds>`; ``endianness`` is either ``LSBFIRST`` or
+    ``MSBFIRST``; mode is one of 0, 1, 2, 3, and specifies which "SPI
+    Mode" is used (see specification docs linked below).
+
+``Spi.begin()``
+
+    A default ``begin`` with no arguments is provided for the lazy; it
+    is equivalent to ``Spi.begin(SPI_1_125MHZ, MSBFIRST, 0)``.
+
+``Spi.send(data, size)``
+
+    Writes data into the port buffer to be transmitted as soon as
+    possible.  ``data`` should be an array of type ``byte*``; ``size``
+    should be the number of elements in ``data``.
+
+Recommended Reading
+-------------------
+
+* `Wikipedia Article on Serial Peripheral Interface Bus (SPI)
+  <http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus>`_
+* `Arduino reference on SPI
+  <http://www.arduino.cc/playground/Code/Spi>`_
+* `Hardcore SPI on Arduino <http://klk64.com/arduino-spi/>`_ by kik64
+* STMicro documentation for STM32F103RB microcontroller:
+
+  * `All <http://www.st.com/mcu/devicedocs-STM32F103RB-110.html>`_
+  * `Datasheet (pdf)
+    <http://www.st.com/stonline/products/literature/ds/13587.pdf>`_
+  * `Reference Manual (pdf)
+    <http://www.st.com/stonline/products/literature/rm/13902.pdf>`_
+