DS3231RTC_alarm.ino

// Arduino DS3232RTC Library
// https://github.com/JChristensen/DS3232RTC
//
// Example sketch illustrating Time library with Real Time Clock.
// This example is identical to the example provided with the Time Library,
// only the #include statement has been changed to include the DS3232RTC library.

#include <DS3232RTC.h>      // https://github.com/JChristensen/DS3232RTC

#include <LowPower.h>


// pin definitions
const uint8_t alarmInput(2);

const int LED_PIN = 8;
const int SQW_PIN = 2;
const int BUTTON_PIN = 3;

boolean alarm_1_called = false;

void turnLedOn() {
  digitalWrite(LED_PIN, HIGH);
  
  // Would perhaps be more convenient to call RTC.alarm(ALARM_1) here,
  //  but that breaks this ISR.
  alarm_1_called = true;
}

void turnLedOff() {
  digitalWrite(LED_PIN, LOW);
}

void setup()
{
    Serial.begin(115200);

    // initialize the alarms to known values, clear the alarm flags, clear the alarm interrupt flags
    RTC.setAlarm(ALM1_MATCH_DATE, 0, 0, 0, 1);
    RTC.setAlarm(ALM2_MATCH_DATE, 0, 0, 0, 1);
    RTC.alarm(ALARM_1);
    RTC.alarm(ALARM_2);
    RTC.alarmInterrupt(ALARM_1, false);
    RTC.alarmInterrupt(ALARM_2, false);
    RTC.squareWave(SQWAVE_NONE);
    
    pinMode(SQW_PIN, INPUT_PULLUP);
    pinMode(BUTTON_PIN, INPUT_PULLUP);
    pinMode(LED_PIN, OUTPUT);

    // set Alarm 1 to occur every second
    RTC.setAlarm(ALM1_EVERY_SECOND, 0, 0, 0, 0);
    // clear the alarm flag
    RTC.alarm(ALARM_1);
    // configure the INT/SQW pin for "interrupt" operation (disable square wave output)
    RTC.squareWave(SQWAVE_NONE);
    // enable interrupt output for Alarm 1
    RTC.alarmInterrupt(ALARM_1, true);
    
    attachInterrupt(digitalPinToInterrupt(SQW_PIN), turnLedOn, FALLING);
    attachInterrupt(digitalPinToInterrupt(BUTTON_PIN), turnLedOff, FALLING);
}

void loop()
{
    if (alarm_1_called)
    {
        RTC.alarm(ALARM_1);
    }
    LowPower.powerDown(SLEEP_FOREVER, ADC_OFF, BOD_OFF);
}