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
A note of callbacks used by functions and class methods of
all these callbacks should be considered as executing in an interrupt context.
This is true for both physical devices with IDs >= 0 and “virtual” devices
with negative IDs like -1 (these “virtual” devices are still thin shims on
top of real hardware and real hardware interrupts). See 编写中断函数.
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.
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).
Return a 24-bit software generated random number.
- class Pin – control I/O pins
- class Signal – control and sense external I/O devices
- class ADC – analog to digital conversion
- class ADCChannel — read analog values from internal or external sources
- class UART – duplex serial communication bus
- class SPI – a Serial Peripheral Interface bus protocol (master side)
- class I2C – a two-wire serial protocol
- class RTC – real time clock
- class Timer – control hardware timers
- class WDT – watchdog timer
- class SD – secure digital memory card