circuitpython/docs/library/machine.rst

:mod:`machine` --- functions related to the hardware
====================================================

.. module:: machine
   :synopsis: functions related to the hardware

The ``machine`` module contains specific functions related to the hardware
on a particular board. Most functions in this module allow to achieve direct
and unrestricted access to and control of hardware blocks on a system
(like CPU, timers, buses, etc.). Used incorrectly, this can lead to
malfunction, lockups, crashes of your board, and in extreme cases, hardware
damage.

.. _machine_callbacks:

A note of callbacks used by functions and class methods of :mod:`machine` module:
all these callbacks should be considered as executing in an interrupt context.
This is true for both physical devices with IDs >= 0 and "virtual" devices
with negative IDs like -1 (these "virtual" devices are still thin shims on
top of real hardware and real hardware interrupts). See :ref:`isr_rules`.

Reset related functions
-----------------------

.. function:: reset()

   Resets the device in a manner similar to pushing the external RESET
   button.

.. function:: soft_reset()

   Performs a soft reset of the interpreter, deleting all Python objects and
   resetting the Python heap.  It tries to retain the method by which the user
   is connected to the MicroPython REPL (eg serial, USB, Wifi).

.. function:: reset_cause()

   Get the reset cause. See :ref:`constants <machine_constants>` for the possible return values.

.. function:: bootloader([value])

   Reset the device and enter its bootloader.  This is typically used to put the
   device into a state where it can be programmed with new firmware.

   Some ports support passing in an optional *value* argument which can control
   which bootloader to enter, what to pass to it, or other things.

Interrupt related functions
---------------------------

The following functions allow control over interrupts.  Some systems require
interrupts to operate correctly so disabling them for long periods may
compromise core functionality, for example watchdog timers may trigger
unexpectedly.  Interrupts should only be disabled for a minimum amount of time
and then re-enabled to their previous state.  For example::

    import machine

    # Disable interrupts
    state = machine.disable_irq()

    # Do a small amount of time-critical work here

    # Enable interrupts
    machine.enable_irq(state)


.. function:: disable_irq()

   Disable interrupt requests.
   Returns the previous IRQ state which should be considered an opaque value.
   This return value should be passed to the `enable_irq()` function to restore
   interrupts to their original state, before `disable_irq()` was called.

.. function:: enable_irq(state)

   Re-enable interrupt requests.
   The *state* parameter should be the value that was returned from the most
   recent call to the `disable_irq()` function.

Power related functions
-----------------------

.. function:: freq([hz])

    Returns the CPU frequency in hertz.

    On some ports this can also be used to set the CPU frequency by passing in *hz*.

.. function:: idle()

   Gates the clock to the CPU, useful to reduce power consumption at any time during
   short or long periods. Peripherals continue working and execution resumes as soon
   as any interrupt is triggered (on many ports this includes system timer
   interrupt occurring at regular intervals on the order of millisecond).

.. function:: sleep()

   .. note:: This function is deprecated, use `lightsleep()` instead with no arguments.

.. function:: lightsleep([time_ms])
              deepsleep([time_ms])

   Stops execution in an attempt to enter a low power state.

   If *time_ms* is specified then this will be the maximum time in milliseconds that
   the sleep will last for.  Otherwise the sleep can last indefinitely.

   With or without a timeout, execution may resume at any time if there are events
   that require processing.  Such events, or wake sources, should be configured before
   sleeping, like `Pin` change or `RTC` timeout.

   The precise behaviour and power-saving capabilities of lightsleep and deepsleep is
   highly dependent on the underlying hardware, but the general properties are:

   * A lightsleep has full RAM and state retention.  Upon wake execution is resumed
     from the point where the sleep was requested, with all subsystems operational.

   * A deepsleep may not retain RAM or any other state of the system (for example
     peripherals or network interfaces).  Upon wake execution is resumed from the main
     script, similar to a hard or power-on reset. The `reset_cause()` function will
     return `machine.DEEPSLEEP` and this can be used to distinguish a deepsleep wake
     from other resets.

.. function:: wake_reason()

   Get the wake reason. See :ref:`constants <machine_constants>` for the possible return values.

   Availability: ESP32, WiPy.

Miscellaneous functions
-----------------------

.. function:: unique_id()

   Returns a byte string with a unique identifier of a board/SoC. It will vary
   from a board/SoC instance to another, if underlying hardware allows. Length
   varies by hardware (so use substring of a full value if you expect a short
   ID). In some MicroPython ports, ID corresponds to the network MAC address.

.. function:: time_pulse_us(pin, pulse_level, timeout_us=1000000, /)

   Time a pulse on the given *pin*, and return the duration of the pulse in
   microseconds.  The *pulse_level* argument should be 0 to time a low pulse
   or 1 to time a high pulse.

   If the current input value of the pin is different to *pulse_level*,
   the function first (*) waits until the pin input becomes equal to *pulse_level*,
   then (**) times the duration that the pin is equal to *pulse_level*.
   If the pin is already equal to *pulse_level* then timing starts straight away.

   The function will return -2 if there was timeout waiting for condition marked
   (*) above, and -1 if there was timeout during the main measurement, marked (**)
   above. The timeout is the same for both cases and given by *timeout_us* (which
   is in microseconds).

.. function:: bitstream(pin, encoding, timing, data, /)

   Transmits *data* by bit-banging the specified *pin*. The *encoding* argument
   specifies how the bits are encoded, and *timing* is an encoding-specific timing
   specification.

   The supported encodings are:

     - ``0`` for "high low" pulse duration modulation. This will transmit 0 and
       1 bits as timed pulses, starting with the most significant bit.
       The *timing* must be a four-tuple of nanoseconds in the format
       ``(high_time_0, low_time_0, high_time_1, low_time_1)``. For example,
       ``(400, 850, 800, 450)`` is the timing specification for WS2812 RGB LEDs
       at 800kHz.

   The accuracy of the timing varies between ports. On Cortex M0 at 48MHz, it is
   at best +/- 120ns, however on faster MCUs (ESP8266, ESP32, STM32, Pyboard), it
   will be closer to +/-30ns.

   .. note:: For controlling WS2812 / NeoPixel strips, see the :mod:`neopixel`
      module for a higher-level API.

.. function:: rng()

   Return a 24-bit software generated random number.

   Availability: WiPy.

.. _machine_constants:

Constants
---------

.. data:: machine.IDLE
          machine.SLEEP
          machine.DEEPSLEEP

    IRQ wake values.

.. data:: machine.PWRON_RESET
          machine.HARD_RESET
          machine.WDT_RESET
          machine.DEEPSLEEP_RESET
          machine.SOFT_RESET

    Reset causes.

.. data:: machine.WLAN_WAKE
          machine.PIN_WAKE
          machine.RTC_WAKE

    Wake-up reasons.

Classes
-------

.. toctree::
   :maxdepth: 1

   machine.Pin.rst
   machine.Signal.rst
   machine.ADC.rst
   machine.ADCBlock.rst
   machine.PWM.rst
   machine.UART.rst
   machine.SPI.rst
   machine.I2C.rst
   machine.I2S.rst
   machine.RTC.rst
   machine.Timer.rst
   machine.WDT.rst
   machine.SD.rst
   machine.SDCard.rst