.. 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.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: 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