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class RTC – real time clock

The RTC is an independent clock that keeps track of the date and time.

Example usage:

rtc = machine.RTC()
rtc.datetime((2020, 1, 21, 2, 10, 32, 36, 0))


class machine.RTC(id=0, ...)

Create an RTC object. See init for parameters of initialization.



Get or set the date and time of the RTC.

With no arguments, this method returns an 8-tuple with the current date and time. With 1 argument (being an 8-tuple) it sets the date and time.

The 8-tuple has the following format:

(year, month, day, weekday, hours, minutes, seconds, subseconds)

The meaning of the subseconds field is hardware dependent.


Initialise the RTC. Datetime is a tuple of the form:

(year, month, day[, hour[, minute[, second[, microsecond[, tzinfo]]]]])

Get get the current datetime tuple.


Resets the RTC to the time of January 1, 2015 and starts running it again.

RTC.alarm(id, time, *, repeat=False)

Set the RTC alarm. Time might be either a millisecond value to program the alarm to current time + time_in_ms in the future, or a datetimetuple. If the time passed is in milliseconds, repeat can be set to True to make the alarm periodic.


Get the number of milliseconds left before the alarm expires.


Cancel a running alarm.

RTC.irq(*, trigger, handler=None, wake=machine.IDLE)

Create an irq object triggered by a real time clock alarm.

  • trigger must be RTC.ALARM0

  • handler is the function to be called when the callback is triggered.

  • wake specifies the sleep mode from where this interrupt can wake up the system.


RTC.memory(data) will write data to the RTC memory, where data is any object which supports the buffer protocol (including bytes, bytearray, memoryview and array.array). RTC.memory() reads RTC memory and returns a bytes object.

Data written to RTC user memory is persistent across restarts, including machine.soft_reset() and machine.deepsleep().

The maximum length of RTC user memory is 2048 bytes by default on esp32, and 492 bytes on esp8266.

Availability: esp32, esp8266 ports.



irq trigger source