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circuitpython/docs/library/pyb.Pin.rst
Damien George 805fd0cfe6 docs/library: Remove "only" directive from all pyb module docs. 
By virtue of its name, the pyb module would only be available on a pyboard
and so does not need to have conditional "only" directives throughout its
documentation.

These conditionals were added mostly in
cfcf47c064 in the initial development of the
cc3200 port, which had the pyb module before it switched to the machine
module.  And wipy only conditionals were removed from the pyb module
documentation in 4542643025, so there's no
need to retain any more conditionals.
2018-07-18 15:47:44 +10:00

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