IrtcSetAlarm1() sets alarm 1, including seconds.

bool IrtcSetAlarm1(uint8_t mode, uint8_t dayOrDate = 1, uint8_t hour = 0, uint8_t minute = 0, uint8_t second = 0)

void setup() {
  Serial.begin(115200);
  if (!IrtcBegin()) return;  // Check the DS3231 RTC connection and begin operation.
  IrtcSetAlarm1(IRTC_ALARM1_MATCH_HOUR_MINUTE_SECOND, 1, 8, 30, 0);  // Set alarm 1, including seconds.
  IrtcSetAlarm2(IRTC_ALARM2_MATCH_HOUR_MINUTE, 1, 17, 30);  // Set alarm 2 with minute resolution.
  IrtcAlarmEnable(1, true);  // Enable or disable the specified alarm.
  IrtcAlarmEnable(2, true);  // Enable or disable the specified alarm.
}
 
void loop() {
  bool alarm1Enabled = false;
  bool alarm1Triggered = false;
  IrtcAlarmEnabled(1, alarm1Enabled);  // Check whether the specified alarm is enabled.
  if (alarm1Enabled && IrtcAlarmTriggered(1, alarm1Triggered, true) && alarm1Triggered) {  // Check whether an alarm has triggered and optionally clear its status.
    Serial.println(F("alarm 1"));
  }
  delay(50);
}

Run each device's corresponding Begin command first. Check I²C addresses and pin sharing; if the bool return value is false, inspect wiring and power.

← Built-in Command List