Example Code for Arduino-Alarm Trigger

Hardware Preparation

• DFR0216-2 DFRduino UNO R3 with IO Expansion Shield and USB Cable A-B x 1
• DFR0641 DS3231M MEMS Precise RTC Module x 1
• FIT0916-FF DuPont Wires x5

Software Preparation

• Download Arduino IDE: Click to download Arduino IDE
• Download the DFRobot_DS3231M library: DFRobot DS3231M library
• About how to install the library?

Wiring Diagram

Other Preparation Work

• Install the DS3231M Library in Arduino IDE.
• Connect the DS3231M module to the Arduino UNO R3 using jumper wires as per the Wiring Diagram.

Sample Code

    /*!
     * @file setAlarmInQuery.ino
     * @brief Set alarm clock 
     * @n Experiment phenomenon: set the alarm clock to trigger at a sepcified time
     * @n           Trigger when the set time of clock is the same with the RTC time
     *
     * @copyright	Copyright (c) 2010 DFRobot Co.Ltd (https://www.dfrobot.com)
     * @licence     The MIT License (MIT)
     * @author [LuoYufeng]([email protected])
     * @version  V0.1
     * @date  2019-08-19
     * @url https://github.com/DFRobot/DFRobot_DS3231M
     */
    #include "DFRobot_DS3231M.h"
    
    DFRobot_DS3231M rtc;
    
    void setup(void)
    {
        Serial.begin(9600);
        /*Wait for the chip to be initialized completely, and then exit*/
        while(rtc.begin() != true){
            Serial.println("failed to init chip, please check if the chip connection is fine");
            delay(1000);
        }
        /*!
         *@brief Set the vaule of pin sqw
         *@param mode eDS3231M_OFF             = 0x01 // Not output square wave, enter interrupt mode
         *@n          eDS3231M_SquareWave_1Hz  = 0x00 // 1Hz square wave
         *@n          eDS3231M_SquareWave_1kHz = 0x08 // 1kHz square wave
         *@n          eDS3231M_SquareWave_4kHz = 0x10 // 4kHz square wave
         *@n          eDS3231M_SquareWave_8kHz = 0x18 // 8kHz square wave
         */
        rtc.writeSqwPinMode(eDS3231M_OFF);
        /*!
         *@brief Set alarm clock
         *@param alarmType Alarm clock working mode typedef enum{
         *@n                                  eEverySecond,
         *@n                                  eSecondsMatch,
         *@n                                  eSecondsMinutesMatch,
         *@n                                  eSecondsMinutesHoursMatch,
         *@n                                  eSecondsMinutesHoursDateMatch,
         *@n                                  eSecondsMinutesHoursDayMatch, //Alarm1
         *@n                                  eEveryMinute,
         *@n                                  eMinutesMatch,
         *@n                                  eMinutesHoursMatch,
         *@n                                  eMinutesHoursDateMatch,
         *@n                                  eMinutesHoursDayMatch,        //Alarm2
         *@n                                  eUnknownAlarm
         *@n                                  }eAlarmTypes;
         *@param days    Alarm clock Day (day)
         *@param hours   Alarm clock Hour (hour)
         *@param mode:   e24hours, eAM, ePM
         *@param minutes Alarm clock (minute)
         *@param seconds Alarm clock (second)
         */
        rtc.setAlarm(eSecondsMatch,/*date,0-30*/27,/*hour,1-12 in 12hours,0-23 in 24hours*/12,eAM,/*minute,0-59*/0,/*second,0-59*/0);
        rtc.setAlarm(eMinutesHoursDateMatch,/*date,0-30*/27,/*hour,1-12 in 12hours,0-23 in 24hours*/12,eAM,/*minute,0-59*/0,/*second,0-59*/0);
        
        rtc.setYear(19);//Set year, default in the 21st century,
        rtc.setMonth(8);
        rtc.setDate(26);
        /*!
         *@brief Set the hours and 12hours or 24hours
         *@param hour:1-12 in 12hours,0-23 in 24hours
         *@param mode:e24hours, eAM, ePM
         */
        rtc.setHour(11,ePM);//1-12 in 12hours,0-23 in 24hours
        rtc.setMinute(59);
        rtc.setSecond(50);
        rtc.adjust();
    }
    void loop() {
        /*!
         *@brief Get current time data 
         *@return Current time data
         */
        rtc.getNowTime();
        /*!
         *@brief Judge if the alarm clock is triggered
         *@return true, triggered; false, not triggered
         */
        if (rtc.isAlarm()){ // If the alarm bit is set
            Serial.println("Alarm clock is triggered.");
            /*!
             *@brief Clear trigger flag
             */
            rtc.clearAlarm();
        }
        Serial.print(rtc.year(), DEC);
        Serial.print('/');
        Serial.print(rtc.month(), DEC);
        Serial.print('/');
        Serial.print(rtc.day(), DEC);
        Serial.print(" (");
        Serial.print(rtc.getDayOfTheWeek());
        Serial.print(") ");
        Serial.print(rtc.hour(), DEC);
        Serial.print(':');
        Serial.print(rtc.minute(), DEC);
        Serial.print(':');
        Serial.print(rtc.second(), DEC);
        Serial.print(' ');
        /*if rtc works in 24hours mode,this function doesn't print anything*/
        Serial.print(rtc.getAMorPM());
        Serial.println();
        if (rtc.lostPower()) {
            Serial.println("RTC lost power, please reset the time!");
        }
        delay(1000);
    }

Result

The serial port prints the time and triggers an interrupt at the specified time.

Additional Information

NOTE: If the hour systems of the clock and alarm clock are not the same, the alarm clock will not be triggered. For example: the clock is 24-hour system, and the alarm clock is 12-hour system.