class RTC – Real Time Clock

The RTC is used to keep track of the date and time.

Quick Usage Example

from machine import RTC

rtc = RTC()
rtc.init((2014, 5, 1, 4, 13, 0, 0, 0))


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

Create an RTC object. See init for parameters of initialisation.:

# id of the RTC may be set if multiple are connected. Defaults to id = 0.
rtc = RTC(id=0)


rtc.init(datetime=None, source=RTC.INTERNAL_RC)

Initialize the RTC. The arguments are:

  • datetime when passed it sets the current time. It is a tuple of the form: (year, month, day[, hour[, minute[, second[, microsecond[, tzinfo]]]]]).
  • source selects the oscillator that drives the RTC. The options are RTC.INTERNAL_RC and RTC.XTAL_32KHZ

For example:

# for 2nd of February 2017 at 10:30am (TZ 0)
rtc.init((2017, 2, 28, 10, 30, 0, 0, 0))

tzinfo is ignored by this method. Use time.timezone to achieve similar results.

Get get the current datetime tuple:

# returns datetime tuple
rtc.ntp_sync(server, * , update_period=3600)

Set up automatic fetch and update the time using NTP (SNTP).

  • server is the URL of the NTP server. Can be set to None to disable the periodic updates.
  • update_period is the number of seconds between updates. Shortest period is 15 seconds.

Can be used like:

rtc.ntp_sync("") # this is an example. You can select a more specific server according to your geographical location

Returns True if the last ntp_sync has been completed, False otherwise:




clock source

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