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158 lines
4.6 KiB
Markdown
158 lines
4.6 KiB
Markdown
---
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title: "Pin"
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aliases:
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- firmwareapi/pycom/machine/pin.html
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- firmwareapi/pycom/machine/pin.md
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- chapter/firmwareapi/pycom/machine/pin
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---
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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.
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## Quick Usage Example
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```python
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from machine import Pin
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# initialize `P9` in gpio mode and make it an output
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p_out = Pin('P9', mode=Pin.OUT)
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p_out.value(1)
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p_out.value(0)
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p_out.toggle()
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p_out(True)
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# make `P10` an input with the pull-up enabled
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p_in = Pin('P10', mode=Pin.IN, pull=Pin.PULL_UP)
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p_in() # get value, 0 or 1
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```
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## Constructors
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#### class machine.Pin(id, ...)
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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()](../pin#pin-init-mode-pull-alt)
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```python
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from machine import Pin
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p = Pin('P10', mode=Pin.OUT, pull=None, alt=-1)
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```
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## Methods
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#### pin.init(mode, pull, \* , alt)
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Initialise the pin:
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* `mode` can be one of:
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* `Pin.IN` - input pin.
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* `Pin.OUT` - output pin in push-pull mode.
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* `Pin.OPEN_DRAIN` - input or output pin in open-drain mode.
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* `pull` can be one of:
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* `None` - no pull up or down resistor.
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* `Pin.PULL_UP` - pull up resistor enabled.
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* `Pin.PULL_DOWN` - pull down resistor enabled.
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* `alt` is the id of the alternate function.
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Returns: `None`.
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#### pin.id()
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Get the pin id.
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#### 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 anything that converts to a boolean. If it converts to True, the pin is set high, otherwise it is set low.
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#### pin(\[value\])
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Pin objects are callable. The call method provides a (fast) shortcut to set and get the value of the pin.
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Example:
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```python
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from machine import Pin
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pin = Pin('P12', mode=Pin.IN, pull=Pin.PULL_UP)
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pin() # fast method to get the value
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```
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See `pin.value()` for more details.
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#### pin.toggle()
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Toggle the value of the pin.
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#### pin.mode(\[mode\])
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Get or set the pin mode.
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#### pin.pull(\[pull\])
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Get or set the pin pull.
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#### pin.hold(\[hold\])
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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.
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These are: `P2, P3, P4, P6, P8, P9, P10, P13, P14, P15, P16, P17, P18, P19, P20, P21, P22, P23`
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#### pin.callback(trigger, handler=None, arg=None)
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Set a callback to be triggered when the input level at the pin changes.
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* `trigger` is the type of event that triggers the callback. Possible values are:
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* `Pin.IRQ_FALLING` interrupt on falling edge.
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* `Pin.IRQ_RISING` interrupt on rising edge.
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* `Pin.IRQ_LOW_LEVEL` interrupt on low level.
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* `Pin.IRQ_HIGH_LEVEL` interrupt on high level.
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The values can be OR-ed together, for instance `trigger=Pin.IRQ_FALLING | Pin.IRQ_RISING`
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* `handler` is the function to be called when the event happens. This function will receive one argument. Set `handler` to `None` to disable it.
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* `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.
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Example:
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```python
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from machine import Pin
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def pin_handler(arg):
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print("got an interrupt in pin %s" % (arg.id()))
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p_in = Pin('P10', mode=Pin.IN, pull=Pin.PULL_UP)
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p_in.callback(Pin.IRQ_FALLING | Pin.IRQ_RISING, pin_handler)
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```
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{{% hint style="info" %}}
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For more information on how Pycom's products handle interrupts, see [here](../../../notes.md#interrupt-handling).
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{{< /hint >}}
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## Attributes
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#### class pin.exp\_board
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Contains all Pin objects supported by the expansion board. Examples:
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```python
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Pin.exp_board.G16
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led = Pin(Pin.exp_board.G16, mode=Pin.OUT)
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Pin.exp_board.G16.id()
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```
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#### class pin.module
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Contains all `Pin` objects supported by the module. Examples:
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```python
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Pin.module.P9
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led = Pin(Pin.module.P9, mode=Pin.OUT)
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Pin.module.P9.id()
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```
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## Constants
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The following constants are used to configure the pin objects. Note that not all constants are available on all ports.
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* Selects the pin mode: `Pin.IN`, `Pin.OUT`, `Pin.OPEN_DRAIN`
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* Enables the pull up or pull down resistor: `Pin.PULL_UP`, `Pin.PULL_DOWN`
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