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machine — 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.

machine.mem8

Read/write 8 bits of memory.

machine.mem16

Read/write 16 bits of memory.

machine.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):

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

value = mem32[0x40001000]

will return a negative value, that could be counter-intuitive.

To always read a positive integer

value = mem32[0x40001000] & 0xffffffff

machine.mem_backup(region=0)

Return a writable memoryview over a persistent hardware memory region that survives at least 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 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

machine.reset()

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

machine.soft_reset()

Performs a soft reset of the interpreter, deleting all Python objects and resetting the Python heap.

machine.reset_cause()

Get the reset cause. See constants for the possible return values.

machine.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)

machine.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.

machine.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

machine.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.

machine.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 lightsleep(), time.sleep() and time.sleep_ms() functions.

machine.sleep()

Note

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

machine.lightsleep([time_ms])

machine.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.

machine.wake_reason()

Get the wake reason. See constants for the possible return values.

Availability: ESP32, WiPy.

machine.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

machine.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.

machine.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).

machine.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 neopixel module for a higher-level API.

machine.rng()

Return a 24-bit software generated random number.

Availability: WiPy.

Constants

machine.IDLE

machine.SLEEP

machine.DEEPSLEEP

IRQ wake values.

machine.PWRON_RESET

machine.HARD_RESET

machine.WDT_RESET

machine.DEEPSLEEP_RESET

machine.SOFT_RESET

Reset causes.

machine.WLAN_WAKE

machine.PIN_WAKE

machine.RTC_WAKE

Wake-up reasons.

Classes

• class Pin – control I/O pins
• class Signal – control and sense external I/O devices
• class ADC – analog to digital conversion
• class ADCBlock – control ADC peripherals
• class DAC – digital to analog conversion
• class PWM – pulse width modulation
• class UART – duplex serial communication bus
• class SPI – a Serial Peripheral Interface bus protocol (controller side)
• class I2C – a two-wire serial protocol
• class I2CTarget – an I2C target device
• class I2S – Inter-IC Sound bus protocol
• class CAN – Controller Area Network protocol
• class RTC – real time clock
• class Timer – control hardware timers
• class Counter – pulse counter
• class Encoder – quadrature decoding
• class WDT – watchdog timer
• class SD – secure digital memory card (cc3200 port only)
• class SDCard – secure digital memory card
• class USBDevice – USB Device driver