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.. _usart:
USART
=====
A USART is more commonly known a *serial port*. It's used to transmit
information between Maple and another device (like your computer,
another Maple, etc.).
.. contents:: Contents
:local:
Hardware/Circuit Design
-----------------------
.. TODO [0.0.12] Add some more information here (like how you should
.. connect TX_a to RX_b and RX_a to TX_b).
.. TODO [0.0.12/Maple Native] UART4 and UART5, Native links
Each LeafLabs board has at least 3 separate USART devices. In the most
simple use case, the RX and TX pins are used to send data at a
predetermined speed (or *baud rate*). Their usage is documented in
the :ref:`Serial Ports <lang-serial>` language reference page.
Which pins correspond to the USART TX and RX pins are given on your
board's silkscreen, and also in the board-specific USART pin maps
available here:
* :ref:`Maple <maple-usart-map>`
* :ref:`Maple RET6 Edition <maple-ret6-usart-map>`
* :ref:`Maple Mini <maple-mini-usart-map>`
If you use a particular serial port, you cannot also use its
communication pins for other purposes at the same time.
Compatible Devices and Specifications
-------------------------------------
We have successfully used the USART ports with an FT232R-based
USB-serial converter at up to 115200 baud. Higher speeds should
certainly be possible.
Recommended Reading
-------------------
* `Wikipedia article on Universal Asynchronous Receiver/Transmitter
(USART)
<http://en.wikipedia.org/wiki/Universal_asynchronous_receiver/transmitter>`_
* `Arduino Serial reference
<http://arduino.cc/en/Reference/Serial>`_
* ST `Reference Manual RM0008
<http://www.st.com/stonline/products/literature/rm/13902.pdf>`_
(PDF), Chapter 27.
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