1 files changed, 93 insertions, 1 deletions
diff --git a/docs/source/usart.rst b/docs/source/usart.rst
index 30c953a..19b054f 100644
--- a/docs/source/usart.rst
+++ b/docs/source/usart.rst
@@ -4,4 +4,96 @@
  USART
 =======
 
-Stub.
+.. contents::
+   :local:
+
+Hardware/Circuit Design
+-----------------------
+
+The Maple has 3 separate USART devices: ``Serial1``, ``Serial2``, and
+``Serial3``. In the most simple use case, the RX and TX pins are used
+to send data at a predetermined baudrate with the line voltage level
+relative to ground.
+
++-----------+--------+-----+
+|Port       |Function|Pin  |
++===========+========+=====+
+|``Serial1``|TX      |D7   |
+|           |        |     |
+|           |RX      |D8   |
+|           |        |     |
+|           |CK      |D6   |
++-----------+--------+-----+
+|``Serial2``|TX      |D1   |
+|           |        |     |
+|           |RX      |D0   |
+|           |        |     |
+|           |CK      |D10  |
+|           |        |     |
+|           |CTS     |D2   |
+|           |        |     |
+|           |RTS     |D3   |
++-----------+--------+-----+
+|``Serial3``|TX      |D29  |
+|           |        |     |
+|           |RX      |D30  |
+|           |        |     |
+|           |CK      |D31  |
+|           |        |     |
+|           |CTS     |D32  |
+|           |        |     |
+|           |RTS     |D33  |
++-----------+--------+-----+
+
+.. TODO make above less ugly
+
+Compatible Devices and Specifications
+-------------------------------------
+
+We have successfully used the Maple USART ports with an FT232R-based USB-serial converter at up to 115200 baud; higher speeds should certainly be possible.
+
+Function Reference
+------------------
+
+In the following, you may replace ``SerialN`` with ``Serial1``,
+``Serial2``, or ``Serial3``.
+
+``SerialN.begin(baudrate)``
+
+    ``SerialN.begin`` is usually called in `setup()`_ to configure the
+    baudrate of the given serial port and to set up the header pins
+    appropriately. It can be called at any time to reconfigure a port
+    or to change the baudrate. 9600 baud is the generic speed most
+    widely supported by other devices and terminals.
+
+``SerialN.print(...)``/\ ``SerialN.println(...)``
+
+    Writes data into the port buffer to be transmitted as soon as
+    possible. Accepts strings (``char*``). If a raw integer is
+    passed, the corresponding ASCII character will be transmitted; to
+    print out a number in human readable form add a second parameter
+    with the base system. 
+
+    For example, to print out the decimal number '1234' use
+    ``SerialN.print(1234, DEC)``; to print out the binary number
+    '1001', use ``SerialN.print(9, BIN)``.
+
+``SerialN.available()``/\ ``SerialN.read()``
+
+    ``SerialN.read()`` will return the next unread character that has
+    been received over the port. ``SerialN.available()`` returns how
+    many such bytes are available (or zero if none are). If none are
+    available, ``SerialN.read()`` will block/fail, so the usual
+    program structure is to poll with ``SerialN.available`` and only
+    read if a nonzero value is returned.
+
+Recommended Reading
+-------------------
+
+* `Wikipedia article on Universal asynchronous receiver/transmitter (USART) <http://en.wikipedia.org/wiki/Universal_asynchronous_receiver/transmitter>`_
+* `Arduino reference on Serial <http://arduino.cc/en/Reference/Serial>`_
+* STMicro documentation for STM32F103RB microcontroller:
+
+  * `All <http://www.st.com/mcu/devicedocs-STM32F103RB-110.html>`_
+  * `Datasheet <http://www.st.com/stonline/products/literature/ds/13587.pdf>`_ (pdf)
+  * `Reference Manual <http://www.st.com/stonline/products/literature/rm/13902.pdf>`_ (pdf)