.. currentmodule:: pyb
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.Pin.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:
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: Constructors
.. 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.
.. 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.
.. 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
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.
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)
.. 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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