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 subscriptable objects used for raw memory access. Each behaves like a sparse array indexed by byte address: value = memN[addr] reads, memN[addr] = value writes. The address is always a byte address, regardless of the access width.

machine.mem8

Subscriptable 8-bit memory accessor. mem8[addr] reads an int in the range 0-255 from the byte at addr; mem8[addr] = value writes the low 8 bits of value. addr must be aligned to 1 byte (any address).

machine.mem16

Subscriptable 16-bit (halfword) memory accessor. mem16[addr] reads an int in the range 0-65535; mem16[addr] = value writes the low 16 bits. addr must be aligned to 2 bytes.

machine.mem32

Subscriptable 32-bit (word) memory accessor. mem32[addr] reads an int in the range 0-0xFFFFFFFF; mem32[addr] = value writes the low 32 bits. addr must be aligned to 4 bytes.

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

Reset related functions

machine.reset() → None

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

machine.soft_reset() → None

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

machine.reset_cause() → int

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

machine.bootloader(value: int = ..., /) → None

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() → int

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: int) → None

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: int = ..., /) → int

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() → None

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() → None

Note

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

machine.lightsleep(time_ms: int = ..., /) → None

machine.deepsleep(time_ms: int = ..., /) → None

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.

Miscellaneous functions

machine.unique_id() → bytes

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: Pin, pulse_level: int, timeout_us: int = 1000000, /) → int

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: Pin, encoding: int, timing: tuple, data: bytes, /) → None

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.

Constants

machine.IDLE: int

machine.SLEEP: int

machine.DEEPSLEEP: int

IRQ wake values.

machine.PWRON_RESET: int

machine.HARD_RESET: int

machine.WDT_RESET: int

machine.DEEPSLEEP_RESET: int

machine.SOFT_RESET: int

Reset causes.

machine.WLAN_WAKE: int

machine.PIN_WAKE: int

machine.RTC_WAKE: int

Wake-up reasons.

Classes

• class Pin – control I/O pins
• class Signal – control and sense external I/O devices
• class LED – LED Control
• class ADC – analog to digital conversion
• class ADCBlock – control ADC peripherals
• 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 WDT – watchdog timer
• class SDCard – secure digital memory card
• class Counter – pulse counter
• class Encoder – quadrature decoding