325 lines
11 KiB
ReStructuredText
325 lines
11 KiB
ReStructuredText
:mod:`pyb` --- functions related to the board
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=============================================
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.. module:: pyb
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:synopsis: functions related to the board
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The ``pyb`` module contains specific functions related to the board.
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Time related functions
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----------------------
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.. function:: delay(ms)
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Delay for the given number of milliseconds.
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.. function:: udelay(us)
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Delay for the given number of microseconds.
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.. function:: millis()
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Returns the number of milliseconds since the board was last reset.
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The result is always a MicroPython smallint (31-bit signed number), so
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after 2^30 milliseconds (about 12.4 days) this will start to return
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negative numbers.
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Note that if :meth:`pyb.stop()` is issued the hardware counter supporting this
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function will pause for the duration of the "sleeping" state. This
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will affect the outcome of :meth:`pyb.elapsed_millis()`.
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.. function:: micros()
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Returns the number of microseconds since the board was last reset.
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The result is always a MicroPython smallint (31-bit signed number), so
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after 2^30 microseconds (about 17.8 minutes) this will start to return
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negative numbers.
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Note that if :meth:`pyb.stop()` is issued the hardware counter supporting this
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function will pause for the duration of the "sleeping" state. This
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will affect the outcome of :meth:`pyb.elapsed_micros()`.
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.. function:: elapsed_millis(start)
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Returns the number of milliseconds which have elapsed since ``start``.
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This function takes care of counter wrap, and always returns a positive
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number. This means it can be used to measure periods up to about 12.4 days.
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Example::
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start = pyb.millis()
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while pyb.elapsed_millis(start) < 1000:
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# Perform some operation
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.. function:: elapsed_micros(start)
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Returns the number of microseconds which have elapsed since ``start``.
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This function takes care of counter wrap, and always returns a positive
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number. This means it can be used to measure periods up to about 17.8 minutes.
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Example::
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start = pyb.micros()
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while pyb.elapsed_micros(start) < 1000:
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# Perform some operation
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pass
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Reset related functions
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-----------------------
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.. function:: hard_reset()
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Resets the pyboard in a manner similar to pushing the external RESET
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button.
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.. function:: bootloader()
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Activate the bootloader without BOOT\* pins.
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.. function:: fault_debug(value)
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Enable or disable hard-fault debugging. A hard-fault is when there is a fatal
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error in the underlying system, like an invalid memory access.
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If the *value* argument is ``False`` then the board will automatically reset if
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there is a hard fault.
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If *value* is ``True`` then, when the board has a hard fault, it will print the
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registers and the stack trace, and then cycle the LEDs indefinitely.
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The default value is disabled, i.e. to automatically reset.
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Interrupt related functions
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---------------------------
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.. function:: disable_irq()
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Disable interrupt requests.
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Returns the previous IRQ state: ``False``/``True`` for disabled/enabled IRQs
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respectively. This return value can be passed to enable_irq to restore
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the IRQ to its original state.
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.. function:: enable_irq(state=True)
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Enable interrupt requests.
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If ``state`` is ``True`` (the default value) then IRQs are enabled.
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If ``state`` is ``False`` then IRQs are disabled. The most common use of
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this function is to pass it the value returned by ``disable_irq`` to
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exit a critical section.
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Power related functions
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-----------------------
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.. function:: freq([sysclk[, hclk[, pclk1[, pclk2]]]])
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If given no arguments, returns a tuple of clock frequencies:
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(sysclk, hclk, pclk1, pclk2).
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These correspond to:
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- sysclk: frequency of the CPU
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- hclk: frequency of the AHB bus, core memory and DMA
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- pclk1: frequency of the APB1 bus
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- pclk2: frequency of the APB2 bus
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If given any arguments then the function sets the frequency of the CPU,
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and the buses if additional arguments are given. Frequencies are given in
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Hz. Eg freq(120000000) sets sysclk (the CPU frequency) to 120MHz. Note that
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not all values are supported and the largest supported frequency not greater
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than the given value will be selected.
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Supported sysclk frequencies are (in MHz): 8, 16, 24, 30, 32, 36, 40, 42, 48,
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54, 56, 60, 64, 72, 84, 96, 108, 120, 144, 168.
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The maximum frequency of hclk is 168MHz, of pclk1 is 42MHz, and of pclk2 is
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84MHz. Be sure not to set frequencies above these values.
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The hclk, pclk1 and pclk2 frequencies are derived from the sysclk frequency
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using a prescaler (divider). Supported prescalers for hclk are: 1, 2, 4, 8,
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16, 64, 128, 256, 512. Supported prescalers for pclk1 and pclk2 are: 1, 2,
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4, 8. A prescaler will be chosen to best match the requested frequency.
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A sysclk frequency of
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8MHz uses the HSE (external crystal) directly and 16MHz uses the HSI
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(internal oscillator) directly. The higher frequencies use the HSE to
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drive the PLL (phase locked loop), and then use the output of the PLL.
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Note that if you change the frequency while the USB is enabled then
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the USB may become unreliable. It is best to change the frequency
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in boot.py, before the USB peripheral is started. Also note that sysclk
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frequencies below 36MHz do not allow the USB to function correctly.
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.. function:: wfi()
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Wait for an internal or external interrupt.
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This executes a ``wfi`` instruction which reduces power consumption
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of the MCU until any interrupt occurs (be it internal or external),
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at which point execution continues. Note that the system-tick interrupt
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occurs once every millisecond (1000Hz) so this function will block for
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at most 1ms.
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.. function:: stop()
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Put the pyboard in a "sleeping" state.
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This reduces power consumption to less than 500 uA. To wake from this
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sleep state requires an external interrupt or a real-time-clock event.
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Upon waking execution continues where it left off.
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See :meth:`rtc.wakeup` to configure a real-time-clock wakeup event.
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.. function:: standby()
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Put the pyboard into a "deep sleep" state.
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This reduces power consumption to less than 50 uA. To wake from this
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sleep state requires a real-time-clock event, or an external interrupt
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on X1 (PA0=WKUP) or X18 (PC13=TAMP1).
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Upon waking the system undergoes a hard reset.
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See :meth:`rtc.wakeup` to configure a real-time-clock wakeup event.
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Miscellaneous functions
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-----------------------
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.. function:: have_cdc()
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Return True if USB is connected as a serial device, False otherwise.
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.. note:: This function is deprecated. Use pyb.USB_VCP().isconnected() instead.
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.. function:: hid((buttons, x, y, z))
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Takes a 4-tuple (or list) and sends it to the USB host (the PC) to
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signal a HID mouse-motion event.
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.. note:: This function is deprecated. Use :meth:`pyb.USB_HID.send()` instead.
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.. function:: info([dump_alloc_table])
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Print out lots of information about the board.
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.. function:: main(filename)
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Set the filename of the main script to run after boot.py is finished. If
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this function is not called then the default file main.py will be executed.
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It only makes sense to call this function from within boot.py.
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.. function:: mount(device, mountpoint, *, readonly=False, mkfs=False)
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.. note:: This function is deprecated. Mounting and unmounting devices should
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be performed by :meth:`uos.mount` and :meth:`uos.umount` instead.
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Mount a block device and make it available as part of the filesystem.
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``device`` must be an object that provides the block protocol. (The
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following is also deprecated. See :class:`uos.AbstractBlockDev` for the
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correct way to create a block device.)
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- ``readblocks(self, blocknum, buf)``
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- ``writeblocks(self, blocknum, buf)`` (optional)
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- ``count(self)``
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- ``sync(self)`` (optional)
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``readblocks`` and ``writeblocks`` should copy data between ``buf`` and
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the block device, starting from block number ``blocknum`` on the device.
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``buf`` will be a bytearray with length a multiple of 512. If
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``writeblocks`` is not defined then the device is mounted read-only.
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The return value of these two functions is ignored.
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``count`` should return the number of blocks available on the device.
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``sync``, if implemented, should sync the data on the device.
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The parameter ``mountpoint`` is the location in the root of the filesystem
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to mount the device. It must begin with a forward-slash.
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If ``readonly`` is ``True``, then the device is mounted read-only,
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otherwise it is mounted read-write.
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If ``mkfs`` is ``True``, then a new filesystem is created if one does not
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already exist.
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.. function:: repl_uart(uart)
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Get or set the UART object where the REPL is repeated on.
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.. function:: rng()
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Return a 30-bit hardware generated random number.
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.. function:: sync()
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Sync all file systems.
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.. function:: unique_id()
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Returns a string of 12 bytes (96 bits), which is the unique ID of the MCU.
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.. function:: usb_mode([modestr], port=-1, vid=0xf055, pid=-1, msc=(), hid=pyb.hid_mouse, high_speed=False)
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If called with no arguments, return the current USB mode as a string.
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If called with *modestr* provided, attempts to configure the USB mode.
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The following values of *modestr* are understood:
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- ``None``: disables USB
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- ``'VCP'``: enable with VCP (Virtual COM Port) interface
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- ``'MSC'``: enable with MSC (mass storage device class) interface
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- ``'VCP+MSC'``: enable with VCP and MSC
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- ``'VCP+HID'``: enable with VCP and HID (human interface device)
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- ``'VCP+MSC+HID'``: enabled with VCP, MSC and HID (only available on PYBD boards)
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For backwards compatibility, ``'CDC'`` is understood to mean
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``'VCP'`` (and similarly for ``'CDC+MSC'`` and ``'CDC+HID'``).
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The *port* parameter should be an integer (0, 1, ...) and selects which
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USB port to use if the board supports multiple ports. A value of -1 uses
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the default or automatically selected port.
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The *vid* and *pid* parameters allow you to specify the VID (vendor id)
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and PID (product id). A *pid* value of -1 will select a PID based on the
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value of *modestr*.
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If enabling MSC mode, the *msc* parameter can be used to specify a list
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of SCSI LUNs to expose on the mass storage interface. For example
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``msc=(pyb.Flash(), pyb.SDCard())``.
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If enabling HID mode, you may also specify the HID details by
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passing the *hid* keyword parameter. It takes a tuple of
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(subclass, protocol, max packet length, polling interval, report
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descriptor). By default it will set appropriate values for a USB
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mouse. There is also a ``pyb.hid_keyboard`` constant, which is an
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appropriate tuple for a USB keyboard.
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The *high_speed* parameter, when set to ``True``, enables USB HS mode if
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it is supported by the hardware.
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Classes
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-------
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.. toctree::
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:maxdepth: 1
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pyb.Accel.rst
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pyb.ADC.rst
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pyb.CAN.rst
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pyb.DAC.rst
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pyb.ExtInt.rst
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pyb.Flash.rst
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pyb.I2C.rst
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pyb.LCD.rst
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pyb.LED.rst
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pyb.Pin.rst
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pyb.RTC.rst
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pyb.Servo.rst
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pyb.SPI.rst
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pyb.Switch.rst
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pyb.Timer.rst
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pyb.UART.rst
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pyb.USB_HID.rst
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pyb.USB_VCP.rst
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