Lowest consumption issue

Hi Gormd, I read with interest your suggestions regarding attaching the interrupt. Indeed, when I do this the board reset and sleep function are reliable. I was also able to achieve a reliable sleep() and reset if I instantiated an RTCZero object and invoked the begin() method. I am wondering if you have any thoughts on this?

RTCZero rtc;

setup() {
  rtc.begin(false);
}

I took a dive into the ArduinoLowPower code and (the RTCZero library on which it depends) and it appears to me that the attachment of the interrupt is handled by the sleep() method? See the attached code snippets from ArduinoLowPower.cpp. It is odd to me that this doesn't appear to be working. The ArduinoLowPower class instantiates an RTCZero object in the private section. So, it is my understanding, attaching an interrupt as you described would require instantiating another RTC object? Shouldn't there be a compiler error if you attempt to use attachInterrupt on a private object?

class ArduinoLowPowerClass {
	public:
		void idle(void);
		void idle(uint32_t millis);
		void idle(int millis) {
			idle((uint32_t)millis);
		}

		void sleep(void);
		void sleep(uint32_t millis);
		void sleep(int millis) {
			sleep((uint32_t)millis);
		}

		void deepSleep(void);
		void deepSleep(uint32_t millis);
		void deepSleep(int millis) {
			deepSleep((uint32_t)millis);
		}

		void attachInterruptWakeup(uint32_t pin, voidFuncPtr callback, uint32_t mode);

		#ifdef BOARD_HAS_COMPANION_CHIP
		void companionLowPowerCallback(onOffFuncPtr callback) {
			companionSleepCB = callback;
		}
		void companionSleep() {
			companionSleepCB(true);
		}
		void companionWakeup() {
			companionSleepCB(false);
		}
		#endif

		#ifdef ARDUINO_ARCH_NRF52
		void enableWakeupFrom(wakeup_reason peripheral, uint32_t pin = 0xFF, uint32_t event = 0xFF, uint32_t option = 0xFF);
		wakeup_reason wakeupReason();
		#endif

	private:
		void setAlarmIn(uint32_t millis);
		#ifdef ARDUINO_ARCH_SAMD
		RTCZero rtc;
		#endif
		#ifdef BOARD_HAS_COMPANION_CHIP
		void (*companionSleepCB)(bool);
		#endif
};

void ArduinoLowPowerClass::idle(uint32_t millis) {
	setAlarmIn(millis);
	idle();
}

void ArduinoLowPowerClass::setAlarmIn(uint32_t millis) {

	if (!rtc.isConfigured()) {
		attachInterruptWakeup(RTC_ALARM_WAKEUP, NULL, 0);
	}

	uint32_t now = rtc.getEpoch();
	rtc.setAlarmEpoch(now + millis/1000);
	rtc.enableAlarm(rtc.MATCH_HHMMSS);
}

void ArduinoLowPowerClass::attachInterruptWakeup(uint32_t pin, voidFuncPtr callback, uint32_t mode) {

	if (pin > PINS_COUNT) {
		// check for external wakeup sources
		// RTC library should call this API to enable the alarm subsystem
		switch (pin) {
			case RTC_ALARM_WAKEUP:
				rtc.begin(false);
				rtc.attachInterrupt(callback);
			/*case UART_WAKEUP:*/
		}
		return;
	}

	EExt_Interrupts in = g_APinDescription[pin].ulExtInt;
	if (in == NOT_AN_INTERRUPT || in == EXTERNAL_INT_NMI)
    		return;

	//pinMode(pin, INPUT_PULLUP);
	attachInterrupt(pin, callback, mode);

	// enable EIC clock
	GCLK->CLKCTRL.bit.CLKEN = 0; //disable GCLK module
	while (GCLK->STATUS.bit.SYNCBUSY);

	GCLK->CLKCTRL.reg = (uint16_t) (GCLK_CLKCTRL_CLKEN | GCLK_CLKCTRL_GEN_GCLK6 | GCLK_CLKCTRL_ID( GCM_EIC )) ;  //EIC clock switched on GCLK6
	while (GCLK->STATUS.bit.SYNCBUSY);

	GCLK->GENCTRL.reg = (GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_OSCULP32K | GCLK_GENCTRL_ID(6));  //source for GCLK6 is OSCULP32K
	while (GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY);

	GCLK->GENCTRL.bit.RUNSTDBY = 1;  //GCLK6 run standby
	while (GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY);

	// Enable wakeup capability on pin in case being used during sleep
	EIC->WAKEUP.reg |= (1 << in);

	/* Errata: Make sure that the Flash does not power all the way down
     	* when in sleep mode. */

	NVMCTRL->CTRLB.bit.SLEEPPRM = NVMCTRL_CTRLB_SLEEPPRM_DISABLED_Val;
}

Finally, have you by chance tried the same on a MKRWAN1300? I cannot seem to get the MKRWAN1300 below 1.16mA. I have removed the pin initialization from wiring.c and used the method suggested here to attach the interrupt. Still 1.16mA. I am trying to ascertain if the current is being used by the SAMD or the Murata LoRa module but its difficult to tell.

Thank you and kind regards,