226a318897
Use real GPIO pad inversion to allow inverted RX, TX, and controls for the hardware UART and software PIO-emulated serial ports. Adds ``setInvertTX(bool)`` and ``setInvertRX(bool)`` calls to both ports, with ``setInvertControl(bool)`` for the HW UARTS.
75 lines
2.5 KiB
ReStructuredText
75 lines
2.5 KiB
ReStructuredText
Serial Ports (USB and UART)
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===========================
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The Arduino-Pico core implements a software-based Serial-over-USB port
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using the USB ACM-CDC model to support a wide variety of operating
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systems.
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``Serial`` is the USB serial port, and while ``Serial.begin()`` does allow
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specifying a baud rate, this rate is ignored since it is USB-based.
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(Also be aware that this USB ``Serial`` port is responsible for resetting
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the RP2040 during the upload process, following the Arduino standard
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of 1200bps = reset to bootloader).
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The RP2040 provides two hardware-based UARTS with configurable
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pin selection.
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``Serial1`` is ``UART0``, and ``Serial2`` is ``UART1``.
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Configure their pins using the ``setXXX`` calls prior to calling ``begin()``
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.. code:: cpp
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Serial1.setRX(pin);
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Serial1.setTX(pin);
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Serial1.begin(baud);
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The size of the receive FIFO may also be adjusted from the default 32 bytes by
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using the ``setFIFOSize`` call prior to calling ``begin()``
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.. code:: cpp
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Serial1.setFIFOSize(128);
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Serial1.begin(baud);
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The FIFO is normally handled via an interrupt, which reduced CPU load and
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makes it less likely to lose characters.
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For applications where an IRQ driven serial port is not appropriate, use
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``setPollingMode(true)`` before calling ``begin()``
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.. code:: cpp
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Serial1.setPollingMode(true);
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Serial1.begin(300)
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For detailed information about the Serial ports, see the
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Arduino `Serial Reference <https://www.arduino.cc/reference/en/language/functions/communication/serial/>`_ .
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Inversion
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---------
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``Serial1`` and ``Serial2`` can both support inverted input and/or outputs via the methods
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``Serial1/2::setInvertRX(bool invert)`` and ``Serial1/2::setInvertTX(bool invert)`` and
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``Serial1/2::serInvertControl(bool invert)``.
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RP2040 Specific SerialUSB methods
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---------------------------------
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void Serial.ignoreFlowControl(bool ignore)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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In some cases, the target application will not assert the DTR virtual line, thus preventing writing operations to succeed.
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For this reason, the SerialUSB::ignoreFlowControl() method disables the connection's state verification, enabling the program to write on the port, even though the data might be lost.
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bool Serial.dtr()
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~~~~~~~~~~~~~~~~~
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Returns the current state of the DTR virtual line. A USB CDC host (such as the Arduino serial monitor) typically raises the DTR pin when opening the device, and may lower it when closing the device.
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bool Serial.rts()
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~~~~~~~~~~~~~~~~~
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Returns the current state of the RTS virtual line.
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