diff --git a/lib/Low_Power/ArduinoLowPower.cpp b/lib/Low_Power/ArduinoLowPower.cpp
new file mode 100644
index 0000000..4383b0b
--- /dev/null
+++ b/lib/Low_Power/ArduinoLowPower.cpp
@@ -0,0 +1,225 @@
+#if defined(ARDUINO_ARCH_SAMD)
+
+#include "ArduinoLowPower.h"
+
+static void configGCLK6()
+{
+	// 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);
+
+	/* 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;
+}
+
+void ArduinoLowPowerClass::idle() {
+	SCB->SCR &= ~SCB_SCR_SLEEPDEEP_Msk;
+	PM->SLEEP.reg = 2;
+	__DSB();
+	__WFI();
+}
+
+void ArduinoLowPowerClass::idle(uint32_t millis) {
+	setAlarmIn(millis);
+	idle();
+}
+
+void ArduinoLowPowerClass::sleep() {
+	bool restoreUSBDevice = false;
+	
+	if (SERIAL_PORT_USBVIRTUAL) {
+		USBDevice.standby();
+	} else {
+		USBDevice.detach();
+		restoreUSBDevice = true;
+	}
+	
+	// Ralf
+	//USBDevice.detach();
+    //restoreUSBDevice = true;
+	//----------	
+	
+	// Disable systick interrupt:  See https://www.avrfreaks.net/forum/samd21-samd21e16b-sporadically-locks-and-does-not-wake-standby-sleep-mode
+	SysTick->CTRL &= ~SysTick_CTRL_TICKINT_Msk;	
+	SCB->SCR |= SCB_SCR_SLEEPDEEP_Msk;
+	__DSB();
+	__WFI();
+	// Enable systick interrupt
+	SysTick->CTRL |= SysTick_CTRL_TICKINT_Msk;	
+	if (restoreUSBDevice) {
+		USBDevice.attach();
+	}
+}
+
+void ArduinoLowPowerClass::sleep(uint32_t millis) {
+	setAlarmIn(millis);
+	sleep();
+}
+
+void ArduinoLowPowerClass::deepSleep() {
+	sleep();
+}
+
+void ArduinoLowPowerClass::deepSleep(uint32_t millis) {
+	sleep(millis);
+}
+
+void ArduinoLowPowerClass::setAlarmIn(uint32_t millis) {
+
+	if (!rtc.isConfigured()) {
+		attachInterruptWakeup(RTC_ALARM_WAKEUP, NULL, (irq_mode)0);
+	}
+
+	uint32_t now = rtc.getEpoch();
+	rtc.setAlarmEpoch(now + millis/1000);
+	rtc.enableAlarm(rtc.MATCH_YYMMDDHHMMSS);
+}
+
+void ArduinoLowPowerClass::attachInterruptWakeup(uint32_t pin, voidFuncPtr callback, irq_mode 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);
+
+	configGCLK6();
+
+	// Enable wakeup capability on pin in case being used during sleep
+	EIC->WAKEUP.reg |= (1 << in);
+}
+
+void ArduinoLowPowerClass::attachAdcInterrupt(uint32_t pin, voidFuncPtr callback, adc_interrupt mode, uint16_t lo, uint16_t hi)
+{
+	uint8_t winmode = 0;
+
+	switch (mode) {
+		case ADC_INT_BETWEEN:   winmode = ADC_WINCTRL_WINMODE_MODE3; break;
+		case ADC_INT_OUTSIDE:   winmode = ADC_WINCTRL_WINMODE_MODE4; break;
+		case ADC_INT_ABOVE_MIN: winmode = ADC_WINCTRL_WINMODE_MODE1; break;
+		case ADC_INT_BELOW_MAX: winmode = ADC_WINCTRL_WINMODE_MODE2; break;
+		default: return;
+	}
+
+	adc_cb = callback;
+
+	configGCLK6();
+
+	// Configure ADC to use GCLK6 (OSCULP32K)
+	while (GCLK->STATUS.bit.SYNCBUSY) {}
+	GCLK->CLKCTRL.reg = GCLK_CLKCTRL_ID_ADC
+						| GCLK_CLKCTRL_GEN_GCLK6
+						| GCLK_CLKCTRL_CLKEN;
+	while (GCLK->STATUS.bit.SYNCBUSY) {}
+
+	// Set ADC prescaler as low as possible
+	ADC->CTRLB.bit.PRESCALER = ADC_CTRLB_PRESCALER_DIV4;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Configure window mode
+	ADC->WINLT.reg = lo;
+	ADC->WINUT.reg = hi;
+	ADC->WINCTRL.reg = winmode;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Enable window interrupt
+	ADC->INTENSET.bit.WINMON = 1;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Enable ADC in standby mode
+	ADC->CTRLA.bit.RUNSTDBY = 1;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Enable continuous conversions
+	ADC->CTRLB.bit.FREERUN = 1;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Configure input mux
+	ADC->INPUTCTRL.bit.MUXPOS = g_APinDescription[pin].ulADCChannelNumber;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Enable the ADC
+	ADC->CTRLA.bit.ENABLE = 1;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Start continuous conversions
+	ADC->SWTRIG.bit.START = 1;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Enable the ADC interrupt
+	NVIC_EnableIRQ(ADC_IRQn);
+}
+
+void ArduinoLowPowerClass::detachAdcInterrupt()
+{
+	// Disable the ADC interrupt
+	NVIC_DisableIRQ(ADC_IRQn);
+
+	// Disable the ADC
+	ADC->CTRLA.bit.ENABLE = 0;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Disable continuous conversions
+	ADC->CTRLB.bit.FREERUN = 0;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Disable ADC in standby mode
+	ADC->CTRLA.bit.RUNSTDBY = 1;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Disable window interrupt
+	ADC->INTENCLR.bit.WINMON = 1;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Disable window mode
+	ADC->WINCTRL.reg = ADC_WINCTRL_WINMODE_DISABLE;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Restore ADC prescaler
+	ADC->CTRLB.bit.PRESCALER = ADC_CTRLB_PRESCALER_DIV512_Val;
+	while (ADC->STATUS.bit.SYNCBUSY) {}
+
+	// Restore ADC clock
+	while (GCLK->STATUS.bit.SYNCBUSY) {}
+	GCLK->CLKCTRL.reg = GCLK_CLKCTRL_ID_ADC
+						| GCLK_CLKCTRL_GEN_GCLK0
+						| GCLK_CLKCTRL_CLKEN;
+	while (GCLK->STATUS.bit.SYNCBUSY) {}
+
+	adc_cb = nullptr;
+}
+
+void ADC_Handler()
+{
+	// Clear the interrupt flag
+	ADC->INTFLAG.bit.WINMON = 1;
+	LowPower.adc_cb();
+}
+
+ArduinoLowPowerClass LowPower;
+
+#endif // ARDUINO_ARCH_SAMD
diff --git a/lib/Low_Power/ArduinoLowPower.h b/lib/Low_Power/ArduinoLowPower.h
new file mode 100644
index 0000000..8ac559a
--- /dev/null
+++ b/lib/Low_Power/ArduinoLowPower.h
@@ -0,0 +1,106 @@
+#ifndef _ARDUINO_LOW_POWER_H_
+#define _ARDUINO_LOW_POWER_H_
+
+#include <Arduino.h>
+
+#ifdef ARDUINO_ARCH_AVR
+#error The library is not compatible with AVR boards
+#endif
+
+#ifdef ARDUINO_ARCH_SAMD
+#include "RTCZero.h"
+#endif
+
+#if defined(ARDUINO_SAMD_TIAN) || defined(ARDUINO_NRF52_PRIMO)
+// add here any board with companion chip which can be woken up
+#define BOARD_HAS_COMPANION_CHIP
+#endif
+
+#define RTC_ALARM_WAKEUP	0xFF
+
+#ifdef ARDUINO_API_VERSION
+using irq_mode = PinStatus;
+#else
+using irq_mode = uint32_t;
+#endif
+
+//typedef void (*voidFuncPtr)( void ) ;
+typedef void (*onOffFuncPtr)( bool ) ;
+
+typedef enum{
+	OTHER_WAKEUP = 0,
+	GPIO_WAKEUP = 1,
+	NFC_WAKEUP = 2,
+	ANALOG_COMPARATOR_WAKEUP = 3
+} wakeup_reason;
+
+#ifdef ARDUINO_ARCH_SAMD
+enum adc_interrupt
+{
+	ADC_INT_BETWEEN,
+	ADC_INT_OUTSIDE,
+	ADC_INT_ABOVE_MIN,
+	ADC_INT_BELOW_MAX,
+};
+#endif
+
+
+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, irq_mode 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
+
+		#ifdef ARDUINO_ARCH_SAMD
+		void attachAdcInterrupt(uint32_t pin, voidFuncPtr callback, adc_interrupt mode, uint16_t lo, uint16_t hi);
+		void detachAdcInterrupt();
+		#endif
+
+	private:
+		void setAlarmIn(uint32_t millis);
+		#ifdef ARDUINO_ARCH_SAMD
+		RTCZero rtc;
+		voidFuncPtr adc_cb;
+		friend void ADC_Handler();
+		#endif
+		#ifdef BOARD_HAS_COMPANION_CHIP
+		void (*companionSleepCB)(bool);
+		#endif
+};
+
+extern ArduinoLowPowerClass LowPower;
+
+#endif
diff --git a/src/main.cpp b/src/main.cpp
index d788307..4719f50 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -39,6 +39,7 @@
 #include <SPI.h>
 #include "hseSensorProtocol.h"
 #include "MessenSensoren.h"
+#include "ArduinoLowPower.h"
 
 // This EUI must be in little-endian format, so least-significant-byte
 // first. When copying an EUI from ttnctl output, this means to reverse
@@ -226,6 +227,9 @@ void onEvent(ev_t ev) {
             }
             // Schedule next transmission
             os_setTimedCallback(&sendjob, os_getTime() + sec2osticks(TX_INTERVAL), do_send);
+
+            LowPower.sleep(1000);
+
             break;
         case EV_LOST_TSYNC:
             Serial.println(F("EV_LOST_TSYNC"));
@@ -276,7 +280,7 @@ void setup() {
     delay(5000);
     //while (!Serial);
     Serial.begin(19200);
-    Serial.println(F("Starting 1.03"));
+    Serial.println(F("Starting 1.04"));
 
 #ifdef __SAMD21G18A__
     Serial.println(F("SAMD21G18A ARM Cortex-M0+ detected"));
@@ -310,6 +314,8 @@ void setup() {
 
 void loop() {
     os_runloop_once();
+    
+
 }