Mistake on this page?
Report an issue in GitHub or email us

RTC

The RTC (Real-Time Clock) class provides mechanisms to set the current time of the hardware RTC with set_time API. The time is set as an offset measured in seconds from the time epoch (Unix Epoch - January 1, 1970).

You can use the attach_rtc API to hook external RTC for using C time functions. It provides you with init(), read(), write() and isenabled() functions to be attached. Time provides more information about C date and time standard library functions.

RTC class APIs are thread safe.

RTC can keep track of time even in a powered down state if the secondary source of power (battery) is connected.

RTC Time class reference

RTC Time example

/* mbed Example Program
 * Copyright (c) 2006-2014 ARM Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include "mbed.h"

int main() {
    set_time(1256729737);  // Set RTC time to Wed, 28 Oct 2009 11:35:37

    while (true) {
        time_t seconds = time(NULL);
        
        printf("Time as seconds since January 1, 1970 = %d\n", seconds);
        
        printf("Time as a basic string = %s", ctime(&seconds));

        char buffer[32];
        strftime(buffer, 32, "%I:%M %p\n", localtime(&seconds));
        printf("Time as a custom formatted string = %s", buffer);
        
        wait(1);
    }
}

Important Information for this Arm website

This site uses cookies to store information on your computer. By continuing to use our site, you consent to our cookies. If you are not happy with the use of these cookies, please review our Cookie Policy to learn how they can be disabled. By disabling cookies, some features of the site will not work.