195 lines
5.5 KiB
ReStructuredText
195 lines
5.5 KiB
ReStructuredText
:mod:`pyb` --- functions related to the pyboard
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===============================================
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.. module:: pyb
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:synopsis: functions related to the pyboard
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The ``pyb`` module contains specific functions related to the pyboard.
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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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.. 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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.. 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 upto 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 upto 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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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 busses 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 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 interrupt.
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This executies a ``wfi`` instruction which reduces power consumption
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of the MCU until an interrupt occurs, at which point execution continues.
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.. function:: standby()
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.. function:: stop()
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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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.. 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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.. function:: info([dump_alloc_table])
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Print out lots of information about the board.
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.. function:: repl_uart(uart)
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Get or set the UART object that 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 for the MCU.
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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.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_VCP.rst
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