: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. Memory access ------------- The module exposes three objects used for raw memory access. .. data:: mem8 Read/write 8 bits of memory. .. data:: mem16 Read/write 16 bits of memory. .. data:: mem32 Read/write 32 bits of memory. Use subscript notation ``[...]`` to index these objects with the address of interest. Note that the address is the byte address, regardless of the size of memory being accessed. Example use (registers are specific to an stm32 microcontroller): .. code-block:: python3 import machine from micropython import const GPIOA = const(0x48000000) GPIO_BSRR = const(0x18) GPIO_IDR = const(0x10) # set PA2 high machine.mem32[GPIOA + GPIO_BSRR] = 1 << 2 # read PA3 value = (machine.mem32[GPIOA + GPIO_IDR] >> 3) & 1 Note: the returned values are signed integers. Example: reading the cpuid register on esp8266 .. code-block:: python3 value = mem32[0x40001000] will return a negative value, that could be counter-intuitive. To always read a positive integer .. code-block:: python3 value = mem32[0x40001000] & 0xffffffff .. function:: mem_backup(region=0) Return a writable `memoryview` over a persistent hardware memory region that survives at least :ref:`soft_reset` on all ports; battery-backed ports also survive power-off. Per-port persistence guarantees vary, see the table below. *region* selects which backup region to access (default 0, the primary region). Pass ``-1`` to get a tuple of all available regions instead. The element type depends on the port's hardware alignment requirements: ``'B'`` (unsigned byte) on ports with byte-addressable backup memory, ``'I'`` (unsigned 32-bit) on ports backed by word-sized registers. Use ``mem.itemsize`` to discover the access granularity at runtime. The total size in bytes is ``len(mem) * mem.itemsize``, where ``len(mem)`` is the number of elements and ``mem.itemsize`` is the size of each element. For example, on a port with 4 word-sized registers, ``len(mem)`` is 4 and ``mem.itemsize`` is 4, giving 16 bytes total. On a port with 4096 bytes of byte-addressable backup SRAM, ``len(mem)`` is 4096 and ``mem.itemsize`` is 1. Cross-port guarantees for portable code: ``mem.itemsize`` is either ``1`` or ``4``; valid indices are ``0..len(mem)-1``; out-of-range access raises ``IndexError``; values are stored in host-native byte order. Region index semantics are not portable, see notes below for ``stm32`` in particular. Usage:: import machine mem = machine.mem_backup() mem[0] = 0x12345678 # write element 0 print(hex(mem[0])) # read element 0 print(len(mem)) # number of elements print(mem.itemsize) # bytes per element print(len(mem) * mem.itemsize) # total bytes available # Discover all available regions for i, r in enumerate(machine.mem_backup(-1)): print(i, len(r), r.itemsize) The total byte size and backing hardware vary by port: ====== =============================================== =========== ============== Port Backing storage Total bytes Battery-backed ====== =============================================== =========== ============== alif Backup SRAM 4096 yes esp32 RTC slow memory 2048 no mimxrt SNVS LPGPR registers (4 per chip) 12-16 yes nrf POWER GPREGRET registers 1-2 no rp2 Watchdog scratch registers 28-60 no samd Backup RAM (SAMD51 only) 8192 yes stm32 Backup SRAM + BKP registers (F4/F7/H5/H7/U5/N6) 2048-8192 yes stm32 RTC BKP registers (other families) 20-128 yes ====== =============================================== =========== ============== .. note:: On esp32 and rp2, data persists across :ref:`soft_reset`, `machine.reset()` and `machine.deepsleep()` wake but is lost on power-off and on poweron-style resets. On esp32 in particular this includes pressing the EN/RESET button on most dev boards, which the chip reports as a power-on reset. Some ports split backup storage across multiple regions, or exclude registers reserved by the bootloader or system firmware: ====== ==================== ================================================ Port Register(s) Note ====== ==================== ================================================ mimxrt LPGPR[3] Excluded; used by TinyUF2 (when used) rp2 scratch[4] Excluded; used by pico-sdk on reset rp2 powman scratch[0..7] Region 2 on RP2350 only stm32 BKP registers Region 1 on BKPSRAM families (F4/F7/H5/H7/U5/N6) ====== ==================== ================================================ Use ``machine.mem_backup(-1)`` to discover available regions and their sizes. On stm32 the region index does not have a uniform meaning across boards: region 0 is BKPSRAM (``itemsize=1``) on BKPSRAM families and BKP registers (``itemsize=4``) on others. Portable code should branch on ``mem.itemsize`` before structuring data. Some registers within a region are accessible but reserved by convention and should not be overwritten. The BKP register file is region 1 on BKPSRAM families and region 0 on the others: ====== ============== ========================================================= Port Register(s) Used by ====== ============== ========================================================= stm32 BKP0R Arduino bootloader (Portenta H7, Giga, Opta, Nicla) stm32 BKP16R-BKP18R ``rfcore_firmware.py`` on STM32WB stm32 last BKP reg clock frequency (``MICROPY_HW_CLK_LAST_FREQ``) stm32 BKP31R (N6) mboot bootloader entry ====== ============== ========================================================= The buffer allows direct register access and can be combined with ``uctypes`` for structured layouts:: import machine, uctypes mem = machine.mem_backup() # Structured access via uctypes (check len(mem) for your board) layout = { "flags": (0 * 4, uctypes.UINT32), # register 0 "counter": (1 * 4, uctypes.UINT32), # register 1 } regs = uctypes.struct(uctypes.addressof(mem), layout) regs.flags = 0x01 print(regs.counter) Availability: alif, esp32, mimxrt, nrf, rp2, samd, stm32 ports. Reset related functions ----------------------- .. function:: reset() :ref:`Hard resets ` the device in a manner similar to pushing the external RESET button. .. function:: soft_reset() Performs a :ref:`soft reset ` of the interpreter, deleting all Python objects and resetting the Python heap. .. function:: reset_cause() Get the reset cause. See :ref:`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, or at most one millisecond after the CPU was paused. It is recommended to call this function inside any tight loop that is continuously checking for an external change (i.e. polling). This will reduce power consumption without significantly impacting performance. To reduce power consumption further then see the :func:`lightsleep`, :func:`time.sleep()` and :func:`time.sleep_ms()` functions. .. function:: sleep() .. note:: This function is deprecated, use :func:`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 ` for the possible return values. Availability: ESP32, WiPy. .. function:: wake_pins() Returns the GPIO pin numbers of those pins which caused wakeup from deep sleep as a tuple of integers. Availability: ESP32. 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.DAC.rst machine.PWM.rst machine.UART.rst machine.SPI.rst machine.I2C.rst machine.I2CTarget.rst machine.I2S.rst machine.CAN.rst machine.RTC.rst machine.Timer.rst machine.Counter.rst machine.Encoder.rst machine.WDT.rst machine.SD.rst machine.SDCard.rst machine.USBDevice.rst