272 lines
7.3 KiB
ReStructuredText
272 lines
7.3 KiB
ReStructuredText
.. currentmodule:: pyb
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.. _pyb.Pin:
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class Pin -- control I/O pins
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=============================
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A pin is the basic object to control I/O pins. It has methods to set
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the mode of the pin (input, output, etc) and methods to get and set the
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digital logic level. For analog control of a pin, see the ADC class.
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Usage Model:
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All Board Pins are predefined as pyb.Pin.board.Name::
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x1_pin = pyb.Pin.board.X1
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g = pyb.Pin(pyb.Pin.board.X1, pyb.Pin.IN)
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CPU pins which correspond to the board pins are available
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as ``pyb.Pin.cpu.Name``. For the CPU pins, the names are the port letter
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followed by the pin number. On the PYBv1.0, ``pyb.Pin.board.X1`` and
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``pyb.Pin.cpu.A0`` are the same pin.
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You can also use strings::
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g = pyb.Pin('X1', pyb.Pin.OUT_PP)
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Users can add their own names::
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MyMapperDict = { 'LeftMotorDir' : pyb.Pin.cpu.C12 }
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pyb.Pin.dict(MyMapperDict)
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g = pyb.Pin("LeftMotorDir", pyb.Pin.OUT_OD)
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and can query mappings::
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pin = pyb.Pin("LeftMotorDir")
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Users can also add their own mapping function::
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def MyMapper(pin_name):
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if pin_name == "LeftMotorDir":
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return pyb.Pin.cpu.A0
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pyb.Pin.mapper(MyMapper)
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So, if you were to call: ``pyb.Pin("LeftMotorDir", pyb.Pin.OUT_PP)``
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then ``"LeftMotorDir"`` is passed directly to the mapper function.
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To summarise, the following order determines how things get mapped into
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an ordinal pin number:
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1. Directly specify a pin object
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2. User supplied mapping function
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3. User supplied mapping (object must be usable as a dictionary key)
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4. Supply a string which matches a board pin
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5. Supply a string which matches a CPU port/pin
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You can set ``pyb.Pin.debug(True)`` to get some debug information about
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how a particular object gets mapped to a pin.
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When a pin has the ``Pin.PULL_UP`` or ``Pin.PULL_DOWN`` pull-mode enabled,
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that pin has an effective 40k Ohm resistor pulling it to 3V3 or GND
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respectively (except pin Y5 which has 11k Ohm resistors).
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Now every time a falling edge is seen on the gpio pin, the callback will be
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executed. Caution: mechanical push buttons have "bounce" and pushing or
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releasing a switch will often generate multiple edges.
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See: http://www.eng.utah.edu/~cs5780/debouncing.pdf for a detailed
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explanation, along with various techniques for debouncing.
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All pin objects go through the pin mapper to come up with one of the
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gpio pins.
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Constructors
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------------
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.. class:: pyb.Pin(id, ...)
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Create a new Pin object associated with the id. If additional arguments are given,
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they are used to initialise the pin. See :meth:`pin.init`.
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Class methods
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-------------
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.. classmethod:: Pin.debug([state])
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Get or set the debugging state (``True`` or ``False`` for on or off).
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.. classmethod:: Pin.dict([dict])
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Get or set the pin mapper dictionary.
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.. classmethod:: Pin.mapper([fun])
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Get or set the pin mapper function.
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Methods
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-------
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.. method:: Pin.init(mode, pull=Pin.PULL_NONE, \*, value=None, alt=-1)
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Initialise the pin:
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- *mode* can be one of:
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- ``Pin.IN`` - configure the pin for input;
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- ``Pin.OUT_PP`` - configure the pin for output, with push-pull control;
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- ``Pin.OUT_OD`` - configure the pin for output, with open-drain control;
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- ``Pin.AF_PP`` - configure the pin for alternate function, pull-pull;
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- ``Pin.AF_OD`` - configure the pin for alternate function, open-drain;
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- ``Pin.ANALOG`` - configure the pin for analog.
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- *pull* can be one of:
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- ``Pin.PULL_NONE`` - no pull up or down resistors;
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- ``Pin.PULL_UP`` - enable the pull-up resistor;
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- ``Pin.PULL_DOWN`` - enable the pull-down resistor.
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- *value* if not None will set the port output value before enabling the pin.
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- *alt* can be used when mode is ``Pin.AF_PP`` or ``Pin.AF_OD`` to set the
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index or name of one of the alternate functions associated with a pin.
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This arg was previously called *af* which can still be used if needed.
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Returns: ``None``.
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.. method:: Pin.value([value])
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Get or set the digital logic level of the pin:
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- With no argument, return 0 or 1 depending on the logic level of the pin.
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- With ``value`` given, set the logic level of the pin. ``value`` can be
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anything that converts to a boolean. If it converts to ``True``, the pin
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is set high, otherwise it is set low.
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.. method:: Pin.__str__()
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Return a string describing the pin object.
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.. method:: Pin.af()
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Returns the currently configured alternate-function of the pin. The
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integer returned will match one of the allowed constants for the af
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argument to the init function.
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.. method:: Pin.af_list()
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Returns an array of alternate functions available for this pin.
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.. method:: Pin.gpio()
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Returns the base address of the GPIO block associated with this pin.
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.. method:: Pin.mode()
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Returns the currently configured mode of the pin. The integer returned
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will match one of the allowed constants for the mode argument to the init
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function.
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.. method:: Pin.name()
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Get the pin name.
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.. method:: Pin.names()
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Returns the cpu and board names for this pin.
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.. method:: Pin.pin()
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Get the pin number.
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.. method:: Pin.port()
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Get the pin port.
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.. method:: Pin.pull()
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Returns the currently configured pull of the pin. The integer returned
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will match one of the allowed constants for the pull argument to the init
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function.
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Constants
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---------
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.. data:: Pin.AF_OD
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initialise the pin to alternate-function mode with an open-drain drive
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.. data:: Pin.AF_PP
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initialise the pin to alternate-function mode with a push-pull drive
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.. data:: Pin.ANALOG
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initialise the pin to analog mode
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.. data:: Pin.IN
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initialise the pin to input mode
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.. data:: Pin.OUT_OD
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initialise the pin to output mode with an open-drain drive
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.. data:: Pin.OUT_PP
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initialise the pin to output mode with a push-pull drive
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.. data:: Pin.PULL_DOWN
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enable the pull-down resistor on the pin
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.. data:: Pin.PULL_NONE
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don't enable any pull up or down resistors on the pin
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.. data:: Pin.PULL_UP
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enable the pull-up resistor on the pin
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class PinAF -- Pin Alternate Functions
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======================================
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A Pin represents a physical pin on the microprocessor. Each pin
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can have a variety of functions (GPIO, I2C SDA, etc). Each PinAF
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object represents a particular function for a pin.
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Usage Model::
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x3 = pyb.Pin.board.X3
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x3_af = x3.af_list()
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x3_af will now contain an array of PinAF objects which are available on
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pin X3.
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For the pyboard, x3_af would contain:
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[Pin.AF1_TIM2, Pin.AF2_TIM5, Pin.AF3_TIM9, Pin.AF7_USART2]
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Normally, each peripheral would configure the af automatically, but sometimes
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the same function is available on multiple pins, and having more control
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is desired.
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To configure X3 to expose TIM2_CH3, you could use::
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pin = pyb.Pin(pyb.Pin.board.X3, mode=pyb.Pin.AF_PP, af=pyb.Pin.AF1_TIM2)
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or::
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pin = pyb.Pin(pyb.Pin.board.X3, mode=pyb.Pin.AF_PP, af=1)
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Methods
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-------
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.. method:: pinaf.__str__()
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Return a string describing the alternate function.
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.. method:: pinaf.index()
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Return the alternate function index.
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.. method:: pinaf.name()
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Return the name of the alternate function.
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.. method:: pinaf.reg()
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Return the base register associated with the peripheral assigned to this
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alternate function. For example, if the alternate function were TIM2_CH3
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this would return stm.TIM2
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