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diff --git a/docs/source/usart.rst b/docs/source/usart.rst new file mode 100644 index 0000000..dbbc81c --- /dev/null +++ b/docs/source/usart.rst @@ -0,0 +1,62 @@ +.. _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: + +.. _usart-circuit: + +Hardware/Circuit Design +----------------------- + +To use a serial port to communicate with an external serial device, +connect the TX pin to your device's RX pin, the RX to your device's TX +pin, and your Maple board's ground to your device's ground. + +.. warning:: Don't connect these pins directly to an RS232 serial + port; they operate at +/- 12V and can damage your board. + +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>` +* :ref:`Maple Native Beta <maple-native-b-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/web/en/resource/technical/document/reference_manual/CD00171190.pdf>`_ + (PDF), Chapter 27. +* `Serial and UART Tutorial + <http://www.freebsd.org/doc/en/articles/serial-uart/>`_ (written for + FreeBSD, but contains a large amount of general information). |