:mod:`pyb` --- functions related to the board
=============================================

.. module:: pyb
   :synopsis: functions related to the board

The ``pyb`` module contains specific functions related to the board.

Time related functions
----------------------

.. function:: delay(ms)

   Delay for the given number of milliseconds.

.. function:: udelay(us)

   Delay for the given number of microseconds.

.. function:: millis()

   Returns the number of milliseconds since the board was last reset.
   
   The result is always a micropython smallint (31-bit signed number), so
   after 2^30 milliseconds (about 12.4 days) this will start to return
   negative numbers.

   Note that if :meth:`pyb.stop()` is issued the hardware counter supporting this
   function will pause for the duration of the "sleeping" state. This
   will affect the outcome of :meth:`pyb.elapsed_millis()`.

.. function:: micros()

   Returns the number of microseconds since the board was last reset.
   
   The result is always a micropython smallint (31-bit signed number), so
   after 2^30 microseconds (about 17.8 minutes) this will start to return
   negative numbers.

   Note that if :meth:`pyb.stop()` is issued the hardware counter supporting this
   function will pause for the duration of the "sleeping" state. This
   will affect the outcome of :meth:`pyb.elapsed_micros()`.

.. function:: elapsed_millis(start)

   Returns the number of milliseconds which have elapsed since ``start``.
   
   This function takes care of counter wrap, and always returns a positive
   number. This means it can be used to measure periods up to about 12.4 days.
   
   Example::

       start = pyb.millis()
       while pyb.elapsed_millis(start) < 1000:
           # Perform some operation

.. function:: elapsed_micros(start)

   Returns the number of microseconds which have elapsed since ``start``.
   
   This function takes care of counter wrap, and always returns a positive
   number. This means it can be used to measure periods up to about 17.8 minutes.
   
   Example::

       start = pyb.micros()
       while pyb.elapsed_micros(start) < 1000:
           # Perform some operation
           pass

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

.. function:: hard_reset()

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

.. function:: bootloader()

   Activate the bootloader without BOOT\* pins.

.. function:: fault_debug(value)

   Enable or disable hard-fault debugging.  A hard-fault is when there is a fatal
   error in the underlying system, like an invalid memory access.

   If the `value` argument is `False` then the board will automatically reset if
   there is a hard fault.

   If `value` is `True` then, when the board has a hard fault, it will print the
   registers and the stack trace, and then cycle the LEDs indefinitely.

   The default value is disabled, i.e. to automatically reset.

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

.. function:: disable_irq()

   Disable interrupt requests.
   Returns the previous IRQ state: ``False``/``True`` for disabled/enabled IRQs
   respectively.  This return value can be passed to enable_irq to restore
   the IRQ to its original state.

.. function:: enable_irq(state=True)

   Enable interrupt requests.
   If ``state`` is ``True`` (the default value) then IRQs are enabled.
   If ``state`` is ``False`` then IRQs are disabled.  The most common use of
   this function is to pass it the value returned by ``disable_irq`` to
   exit a critical section.

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

.. only:: port_pyboard

    .. function:: freq([sysclk[, hclk[, pclk1[, pclk2]]]])
    
       If given no arguments, returns a tuple of clock frequencies:
       (sysclk, hclk, pclk1, pclk2).
       These correspond to:
    
        - sysclk: frequency of the CPU
        - hclk: frequency of the AHB bus, core memory and DMA
        - pclk1: frequency of the APB1 bus
        - pclk2: frequency of the APB2 bus
    
       If given any arguments then the function sets the frequency of the CPU,
       and the busses if additional arguments are given.  Frequencies are given in
       Hz.  Eg freq(120000000) sets sysclk (the CPU frequency) to 120MHz.  Note that
       not all values are supported and the largest supported frequency not greater
       than the given value will be selected.
    
       Supported sysclk frequencies are (in MHz): 8, 16, 24, 30, 32, 36, 40, 42, 48,
       54, 56, 60, 64, 72, 84, 96, 108, 120, 144, 168.
    
       The maximum frequency of hclk is 168MHz, of pclk1 is 42MHz, and of pclk2 is
       84MHz.  Be sure not to set frequencies above these values.
    
       The hclk, pclk1 and pclk2 frequencies are derived from the sysclk frequency
       using a prescaler (divider).  Supported prescalers for hclk are: 1, 2, 4, 8,
       16, 64, 128, 256, 512.  Supported prescalers for pclk1 and pclk2 are: 1, 2,
       4, 8.  A prescaler will be chosen to best match the requested frequency.
    
       A sysclk frequency of
       8MHz uses the HSE (external crystal) directly and 16MHz uses the HSI
       (internal oscillator) directly.  The higher frequencies use the HSE to
       drive the PLL (phase locked loop), and then use the output of the PLL.
    
       Note that if you change the frequency while the USB is enabled then
       the USB may become unreliable.  It is best to change the frequency
       in boot.py, before the USB peripheral is started.  Also note that sysclk
       frequencies below 36MHz do not allow the USB to function correctly.
    
    .. function:: wfi()
    
       Wait for an internal or external interrupt.
    
       This executes a ``wfi`` instruction which reduces power consumption
       of the MCU until any interrupt occurs (be it internal or external),
       at which point execution continues.  Note that the system-tick interrupt
       occurs once every millisecond (1000Hz) so this function will block for
       at most 1ms.
    
    .. function:: stop()
    
       Put the pyboard in a "sleeping" state.
    
       This reduces power consumption to less than 500 uA.  To wake from this
       sleep state requires an external interrupt or a real-time-clock event.
       Upon waking execution continues where it left off.
    
       See :meth:`rtc.wakeup` to configure a real-time-clock wakeup event.
    
    .. function:: standby()
    
       Put the pyboard into a "deep sleep" state.
    
       This reduces power consumption to less than 50 uA.  To wake from this
       sleep state requires a real-time-clock event, or an external interrupt
       on X1 (PA0=WKUP) or X18 (PC13=TAMP1).
       Upon waking the system undergoes a hard reset.
    
       See :meth:`rtc.wakeup` to configure a real-time-clock wakeup event.

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

.. only:: port_pyboard

    .. function:: have_cdc()
    
       Return True if USB is connected as a serial device, False otherwise.
    
       .. note:: This function is deprecated.  Use pyb.USB_VCP().isconnected() instead.
    
    .. function:: hid((buttons, x, y, z))
    
       Takes a 4-tuple (or list) and sends it to the USB host (the PC) to
       signal a HID mouse-motion event.
    
       .. note:: This function is deprecated.  Use :meth:`pyb.USB_HID.send()` instead.
    
    .. function:: info([dump_alloc_table])
    
       Print out lots of information about the board.

.. function:: main(filename)

   Set the filename of the main script to run after boot.py is finished.  If
   this function is not called then the default file main.py will be executed.

   It only makes sense to call this function from within boot.py.

.. only:: port_pyboard

    .. function:: mount(device, mountpoint, \*, readonly=False, mkfs=False)
    
       Mount a block device and make it available as part of the filesystem.
       ``device`` must be an object that provides the block protocol:
    
        - ``readblocks(self, blocknum, buf)``
        - ``writeblocks(self, blocknum, buf)`` (optional)
        - ``count(self)``
        - ``sync(self)`` (optional)
    
       ``readblocks`` and ``writeblocks`` should copy data between ``buf`` and
       the block device, starting from block number ``blocknum`` on the device.
       ``buf`` will be a bytearray with length a multiple of 512.  If
       ``writeblocks`` is not defined then the device is mounted read-only.
       The return value of these two functions is ignored.
    
       ``count`` should return the number of blocks available on the device.
       ``sync``, if implemented, should sync the data on the device.
    
       The parameter ``mountpoint`` is the location in the root of the filesystem
       to mount the device.  It must begin with a forward-slash.
    
       If ``readonly`` is ``True``, then the device is mounted read-only,
       otherwise it is mounted read-write.
    
       If ``mkfs`` is ``True``, then a new filesystem is created if one does not
       already exist.
    
       To unmount a device, pass ``None`` as the device and the mount location
       as ``mountpoint``.

.. function:: repl_uart(uart)

   Get or set the UART object where the REPL is repeated on.

.. only:: port_pyboard

    .. function:: rng()
    
       Return a 30-bit hardware generated random number.

.. function:: sync()

   Sync all file systems.

.. only:: port_pyboard

    .. function:: unique_id()
    
       Returns a string of 12 bytes (96 bits), which is the unique ID of the MCU.

.. function:: usb_mode([modestr], vid=0xf055, pid=0x9801, hid=pyb.hid_mouse)

   If called with no arguments, return the current USB mode as a string.

   If called with ``modestr`` provided, attempts to set USB mode.
   This can only be done when called from ``boot.py`` before
   :meth:`pyb.main()` has been called.  The following values of
   ``modestr`` are understood:

   - ``None``: disables USB
   - ``'VCP'``: enable with VCP (Virtual COM Port) interface
   - ``'VCP+MSC'``: enable with VCP and MSC (mass storage device class)
   - ``'VCP+HID'``: enable with VCP and HID (human interface device)

   For backwards compatibility, ``'CDC'`` is understood to mean
   ``'VCP'`` (and similarly for ``'CDC+MSC'`` and ``'CDC+HID'``).

   The ``vid`` and ``pid`` parameters allow you to specify the VID
   (vendor id) and PID (product id).

   If enabling HID mode, you may also specify the HID details by
   passing the ``hid`` keyword parameter.  It takes a tuple of
   (subclass, protocol, max packet length, polling interval, report
   descriptor).  By default it will set appropriate values for a USB
   mouse.  There is also a ``pyb.hid_keyboard`` constant, which is an
   appropriate tuple for a USB keyboard.

Classes
-------

.. only:: port_pyboard

    .. toctree::
       :maxdepth: 1
    
       pyb.Accel.rst
       pyb.ADC.rst
       pyb.CAN.rst
       pyb.DAC.rst
       pyb.ExtInt.rst
       pyb.I2C.rst
       pyb.LCD.rst
       pyb.LED.rst
       pyb.Pin.rst
       pyb.RTC.rst
       pyb.Servo.rst
       pyb.SPI.rst
       pyb.Switch.rst
       pyb.Timer.rst
       pyb.UART.rst
       pyb.USB_HID.rst
       pyb.USB_VCP.rst
