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diff --git a/source/lang/api/serial.rst b/source/lang/api/serial.rst index a08c9b7..8c9ebc7 100644 --- a/source/lang/api/serial.rst +++ b/source/lang/api/serial.rst @@ -1,31 +1,104 @@ +.. highlight:: cpp + .. _lang-serial: Serial Ports (``Serial1``, ``Serial2``, ``Serial3``) ==================================================== -Used for communication between the Maple board and a computer or other -devices. +This page describes how to use the built-in serial ports (also known +as USARTs). For more information about serial ports, see +:ref:`usart`. .. contents:: Contents :local: -Introduction ------------- - -.. FIXME [0.0.12/Maple Native] UART4, UART5 - -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. +Getting Started +--------------- + +First, decide which serial port you wish to use, and :ref:`connect its +pins to the device you're communicating with <usart-circuit>`. (The TX +and RX pins for a serial port are labeled on your board's silkscreen; +for example, serial port 2 has pins labeled "TX2" and "RX2"). + +The variable for controlling a serial port is the word ``Serial``, +plus the serial port's number. For example, you can control serial +port 1 with the variable ``Serial1``, serial port 2 with ``Serial2``, +and so on. + +In order to get started using your serial port, you'll first need to +turn it on. Do this by calling your serial port's ``begin()`` +function, giving it the baud rate you wish it to communicate at. If +you're not sure what baud rate to use, 9600 is a safe (although slow) +value to try. Put this call to ``begin()`` in your :ref:`lang-setup`, +like in the following example:: + + void setup() { + // 9600 is the baud rate to use. The baud rate determines how + // fast the communication goes. + Serial2.begin(9600); + } + + void loop() { + // Communicate using Serial2 here + } + +Communicating Over Serial +------------------------- + +Now that your serial port is set up, it's time to start communicating. + +One common use for serial ports is to print strings and other +debugging information to a computer. You can print numbers or strings +using ``print()`` and ``println()``, like this:: + + void printSomeInformation() { + Serial2.print("First, print this string. Then print a number: "); + Serial2.print(42); + Serial2.print(". You can print floating point values, too: "); + Serial2.print(3.14); + Serial2.println(". Using println() instead of print() ends the line."); + Serial2.println("This sentence starts on a new line."); + } + +This sort of communication can go both ways: you can send characters +from a computer to a serial port as well. You can check how many +characters are waiting for you to read using the ``available()`` +function, and read them out one at a time using ``read()``. The +following example program uses these functions to "echo" back anything +sent to ``Serial2``:: + + void setup() { + Serial2.begin(9600); + } + + void echoCharacter() { + // Check to see if we have received any information. numUnread + // will hold the number of bytes we've received, but haven't + // looked at yet. + int numUnread = Serial2.available(); + + // numUnread > 0 means that there are some unread bytes waiting + if (numUnread > 0) { + // Read a single byte out: + byte b = Serial2.read(); + // And then print it back: + Serial2.print(b); + } + } + + void loop() { + echoCharacter(); + } + +Function Reference +------------------ + +This section gives a full listing of functions available for use with +serial ports. Library Documentation --------------------- -.. FIXME [0.1.0] Tutorial-style usage introduction - All of the ``Serial[1,2,3]`` objects are instances of the ``HardwareSerial`` class, which is documented in this section. (This means that you can use any of these functions on any of ``Serial1``, @@ -36,14 +109,14 @@ means that you can use any of these functions on any of ``Serial1``, Serial port class. Predefined instances are ``Serial1``, ``Serial2``, and ``Serial3``. -.. cpp:function:: HardwareSerial::begin(unsigned int baud) +.. cpp:function:: void HardwareSerial::begin(unsigned int baud) Set up a ``HardwareSerial`` object for communications. This method must be called before attempting to use the ``HardwareSerial`` object (typically, you call this in your :ref:`setup() <lang-setup>` function). -.. cpp:function:: HardwareSerial::end() +.. cpp:function:: void HardwareSerial::end() Disables the USART associated with this object, allowing any associated communication pins to be used for other purposes. @@ -59,107 +132,106 @@ means that you can use any of these functions on any of ``Serial1``, <HardwareSerial::available>`), the call will block until one becomes available. -.. cpp:function:: HardwareSerial::flush() +.. cpp:function:: void HardwareSerial::flush() Throw away the contents of the serial port's receiver (RX) buffer. That is, clears any buffered characters, so that the next character read is guaranteed to be new. -.. cpp:function:: HardwareSerial::print(unsigned char b) +.. cpp:function:: void HardwareSerial::print(unsigned char b) Print the given byte over the USART. -.. cpp:function:: HardwareSerial::print(char c) +.. cpp:function:: void HardwareSerial::print(char c) Print the given character over the USART. 7-bit clean characters are typically interpreted as ASCII text. -.. cpp:function:: HardwareSerial::print(const char *str) +.. cpp:function:: void HardwareSerial::print(const char *str) Print the given null-terminated string over the USART. -.. cpp:function:: HardwareSerial::print(int n) +.. cpp:function:: void HardwareSerial::print(int n) Print the argument's digits over the USART, in decimal format. Negative values will be prefixed with a ``'-'`` character. -.. cpp:function:: HardwareSerial::print(unsigned int n) +.. cpp:function:: void HardwareSerial::print(unsigned int n) Print the argument's digits over the USART, in decimal format. -.. cpp:function:: HardwareSerial::print(long n) +.. cpp:function:: void HardwareSerial::print(long n) Print the argument's digits over the USART, in decimal format. Negative values will be prefixed with a ``'-'`` character. -.. cpp:function:: HardwareSerial::print(unsigned long n) +.. cpp:function:: void HardwareSerial::print(unsigned long n) Print the argument's digits over the USART, in decimal format. -.. cpp:function:: HardwareSerial::print(long n, int base) +.. cpp:function:: void HardwareSerial::print(long n, int base) Print the digits of ``n`` over the USART, in base ``base`` (which may be between 2 and 16). The ``base`` value 2 corresponds to binary, 8 to octal, 10 to decimal, and 16 to hexadecimal. Negative values will be prefixed with a ``'-'`` character. -.. cpp:function:: HardwareSerial::print(double n) +.. cpp:function:: void HardwareSerial::print(double n) Print ``n``, accurate to 2 digits after the decimal point. .. _lang-serial-println: -.. cpp:function:: HardwareSerial::println(char c) +.. cpp:function:: void HardwareSerial::println(char c) Like ``print(c)``, followed by ``"\r\n"``. -.. cpp:function:: HardwareSerial::println(const char *c) +.. cpp:function:: void HardwareSerial::println(const char *c) Like ``print(c)``, followed by ``"\r\n"``. -.. cpp:function:: HardwareSerial::println(unsigned char b) +.. cpp:function:: void HardwareSerial::println(unsigned char b) Like ``print(b)``, followed by ``"\r\n"``. -.. cpp:function:: HardwareSerial::println(int n) +.. cpp:function:: void HardwareSerial::println(int n) Like ``print(n)``, followed by ``"\r\n"``. -.. cpp:function:: HardwareSerial::println(unsigned int n) +.. cpp:function:: void HardwareSerial::println(unsigned int n) Like ``print(n)``, followed by ``"\r\n"``. -.. cpp:function:: HardwareSerial::println(long n) +.. cpp:function:: void HardwareSerial::println(long n) Like ``print(n)``, followed by ``"\r\n"``. -.. cpp:function:: HardwareSerial::println(unsigned long n) +.. cpp:function:: void HardwareSerial::println(unsigned long n) Like ``print(n)``, followed by ``"\r\n"``. -.. cpp:function:: HardwareSerial::println(long n, int base) +.. cpp:function:: void HardwareSerial::println(long n, int base) Like ``print(n, b)``, followed by ``"\r\n"``. -.. cpp:function:: HardwareSerial::println(double n) +.. cpp:function:: void HardwareSerial::println(double n) Like ``print(n)``, followed by ``"\r\n"``. -.. cpp:function:: HardwareSerial::println() +.. cpp:function:: void HardwareSerial::println() Prints ``"\r\n"`` over the USART. -.. cpp:function:: HardwareSerial::write(unsigned char ch) +.. cpp:function:: void HardwareSerial::write(unsigned char ch) Sends one character over the USART. This function is currently - blocking, although nonblocking writes are a planned future - extension. + blocking. This is a low-level function. One of the ``print()`` or ``println()`` functions is likely to be more useful when printing multiple characters, when formatting numbers for printing, etc. -.. cpp:function:: HardwareSerial::write(const char* str) +.. cpp:function:: void HardwareSerial::write(const char* str) Send the given null-terminated character string over the USART. @@ -167,7 +239,7 @@ means that you can use any of these functions on any of ``Serial1``, ``println()`` functions is likely to be more useful when printing multiple characters, when formatting numbers for printing, etc. -.. cpp:function:: HardwareSerial::write(void *buf, unsigned int size) +.. cpp:function:: void HardwareSerial::write(void *buf, unsigned int size) Writes the first ``size`` bytes of ``buf`` over the USART. Each byte is transmitted as an individual character. @@ -176,6 +248,14 @@ means that you can use any of these functions on any of ``Serial1``, ``println()`` functions is likely to be more useful when printing multiple characters, when formatting numbers for printing, etc. +.. cpp:function:: int HardwareSerial::txPin() + + Return the number of the TX (transmit) pin. + +.. cpp:function:: int HardwareSerial::rxPin() + + Return the number of the RX (receive) pin. + Arduino Compatibility Note -------------------------- |