pycom-documentation/chapter/firmwareapi/pycom/machine/Pin.md

class Pin – Control I/O Pins

A pin is the basic object to control I/O pins (also known as GPIO - general-purpose input/output). 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.

Quick Usage Example

from machine import Pin

# initialize `P9` in gpio mode and make it an output
p_out = Pin('P9', mode=Pin.OUT)
p_out.value(1)
p_out.value(0)
p_out.toggle()
p_out(True)

# make `P10` an input with the pull-up enabled
p_in = Pin('P10', mode=Pin.IN, pull=Pin.PULL_UP)
p_in() # get value, 0 or 1

Constructors

#####class machine.Pin(id, ...)

Create a new Pin object associated with the string id. If additional arguments are given, they are used to initialise the pin. See pin.init().

from machine import Pin
p = Pin('P10', mode=Pin.OUT, pull=None, alt=-1)

Methods

#####pin.init(mode, pull, * , alt)

Initialise the pin:

• mode can be one of:
  • Pin.IN - input pin.
  • Pin.OUT - output pin in push-pull mode.
  • Pin.OPEN_DRAIN - input or output pin in open-drain mode.
• pull can be one of:
  • None - no pull up or down resistor.
  • Pin.PULL_UP - pull up resistor enabled.
  • Pin.PULL_DOWN - pull down resistor enabled.
• alt is the id of the alternate function.

Returns: None.

#####pin.id()

Get the pin id.

#####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.

#####pin([value])

Pin objects are callable. The call method provides a (fast) shortcut to set and get the value of the pin.

Example:

from machine import Pin
pin = Pin('P12', mode=Pin.IN, pull=Pin.PULL_UP)
pin()   # fast method to get the value

See pin.value() for more details.

#####pin.toggle()

Toggle the value of the pin.

#####pin.mode([mode])

Get or set the pin mode.

#####pin.pull([pull])

Get or set the pin pull.

#####pin.hold([hold])

Get or set the pin hold. You can apply a hold to a pin by passing True (or clear it by passing False). When a pin is held, its value cannot be changed by using Pin.value() or Pin.toggle() until the hold is released. This Can be used to retain the pin state through a core reset and system reset triggered by watchdog time-out or Deep-sleep events. Only pins in the RTC power domain can retain their value through deep sleep or reset. These are: P2, P3, P4, P6, P8, P9, P10, P13, P14, P15, P16, P17, P18, P19, P20, P21, P22, P23.

#####pin.callback(trigger, handler=None, arg=None)

Set a callback to be triggered when the input level at the pin changes.

• trigger is the type of event that triggers the callback. Possible values are:
  • Pin.IRQ_FALLING interrupt on falling edge.
  • Pin.IRQ_RISING interrupt on rising edge.
  • Pin.IRQ_LOW_LEVEL interrupt on low level.
  • Pin.IRQ_HIGH_LEVEL interrupt on high level.

The values can be OR-ed together, for instance trigger=Pin.IRQ_FALLING | Pin.IRQ_RISING

• handler is the function to be called when the event happens. This function will receive one argument. Set handler to None to disable it.

• arg is an optional argument to pass to the callback. If left empty or set to None, the function will receive the Pin object that triggered it.

Example:

from machine import Pin

def pin_handler(arg):
    print("got an interrupt in pin %s" % (arg.id()))

p_in = Pin('P10', mode=Pin.IN, pull=Pin.PULL_UP)
p_in.callback(Pin.IRQ_FALLING | Pin.IRQ_RISING, pin_handler)

{% hint style='info' %} For more information on how Pycom’s products handle interrupts, see here. {% endhint %}

Attributes

#####class pin.exp_board

Contains all Pin objects supported by the expansion board. Examples:

Pin.exp_board.G16
led = Pin(Pin.exp_board.G16, mode=Pin.OUT)
Pin.exp_board.G16.id()

#####class pin.module Contains all Pin objects supported by the module. Examples:

Pin.module.P9
led = Pin(Pin.module.P9, mode=Pin.OUT)
Pin.module.P9.id()

Constants

The following constants are used to configure the pin objects. Note that not all constants are available on all ports.

Pin.IN Pin.OUT Pin.OPEN_DRAIN

Selects the pin mode.

Pin.PULL_UP Pin.PULL_DOWN

Enables the pull up or pull down resistor.