diff --git a/EmotiBit.cpp b/EmotiBit.cpp
index 8b2ed0ee..5bdacb78 100644
--- a/EmotiBit.cpp
+++ b/EmotiBit.cpp
@@ -5,10 +5,9 @@
 
 EmotiBit* myEmotiBit = nullptr;
 void(*onInterruptCallback)(void);
-
 #ifdef ARDUINO_FEATHER_ESP32
 TaskHandle_t EmotiBitDataAcquisition;
-hw_timer_t * timer = NULL;
+SemaphoreHandle_t _xMutex; ///< Semaphore to prevent concurrent access of double buffer between acquisition and update tasks 
 #endif
 
 EmotiBit::EmotiBit() 
@@ -1098,20 +1097,9 @@ uint8_t EmotiBit::setup(String firmwareVariant)
 		//Serial.println("Starting interrupts");
 		startTimer(BASE_SAMPLING_FREQ);
 #elif defined ARDUINO_FEATHER_ESP32
-		// setup timer
-		timer = timerBegin(0, 80, true); // timer ticks with APB timer, which runs at 80MHz. This setting makes the timer tick every 1uS
-
-		// Attach onTimer function to our timer.
-		timerAttachInterrupt(timer, &onTimer, true);
-
-		// Set alarm to call onTimer function (value in microseconds).
-		// Repeat the alarm (third parameter)
-		timerAlarmWrite(timer, 1000000 / BASE_SAMPLING_FREQ, true);
-
-		// Start an alarm
-		timerAlarmEnable(timer);
-
-		attachToCore(&ReadSensors, this);
+		_xMutex = xSemaphoreCreateMutex();
+		attachReadSensorsToCore(&ReadSensors, this);
+		attachUpdateToCore(&Update);
 #endif
 	}
 
@@ -1597,6 +1585,7 @@ void EmotiBit::updateButtonPress()
 
 uint8_t EmotiBit::update()
 {
+	
 	if (testingMode == TestingMode::FACTORY_TEST)
 	{
 		processFactoryTestMessages();
@@ -1665,14 +1654,15 @@ uint8_t EmotiBit::update()
 	// NOTE:: An older firmware, v1.2.86 needs to be used to write EDA correction values to V3 (OTP) and below.
 	// Newer FW version can read both NVMs (EEPROM and OTP), but only have write ability for EEPROM
 
-
+	
 	// Handle data buffer reading and sending
 	static uint32_t dataSendTimer = millis();
 	if (millis() - dataSendTimer > DATA_SEND_INTERVAL)
 	{
+		if (myEmotiBit->DIGITAL_WRITE_DEBUG) digitalWrite(myEmotiBit->DEBUG_OUT_PIN_1, HIGH);
+		_freeToSleep = false;  // Sending data involves writing to storage. Dont sleep cores when writing to storage.
 		dataSendTimer = millis();
-
-
+		
 
 		if (_sendTestData)
 		{
@@ -1698,6 +1688,9 @@ uint8_t EmotiBit::update()
 				bufferOverflowTest();
 			}
 		}
+		
+		_freeToSleep = true;
+		if (myEmotiBit->DIGITAL_WRITE_DEBUG) digitalWrite(myEmotiBit->DEBUG_OUT_PIN_1, LOW);
 	}
 
 	// Hibernate after writing data
@@ -1842,7 +1835,7 @@ int8_t EmotiBit::updateThermopileData() {
 #ifdef DEBUG_THERM_UPDATE
 	Serial.println("updateThermopileData");
 #endif
-	if (DIGITAL_WRITE_DEBUG) digitalWrite(DEBUG_OUT_PIN_1, HIGH);
+	
 	// Thermopile
 	int8_t status = 0;
 	uint32_t timestamp;
@@ -1871,12 +1864,11 @@ int8_t EmotiBit::updateThermopileData() {
 #endif
 			if (thermStatus == MLX90632::status::SENSOR_SUCCESS)
 			{
-				if (DIGITAL_WRITE_DEBUG) digitalWrite(DEBUG_OUT_PIN_2, HIGH);
+				
 				timestamp = millis();
 				status = status | therm0AMB.push_back(AMB, &(timestamp));
 				status = status | therm0Sto.push_back(Sto, &(timestamp));
 				thermopile.startRawSensorValues(thermStatus);
-				if (DIGITAL_WRITE_DEBUG) digitalWrite(DEBUG_OUT_PIN_2, LOW);
 			}
 			else
 			{
@@ -1897,7 +1889,7 @@ int8_t EmotiBit::updateThermopileData() {
 	}
 	
 	_thermReadFinishedTime = micros();
-	if (DIGITAL_WRITE_DEBUG) digitalWrite(DEBUG_OUT_PIN_1, LOW);
+	
 	return status;
 }
 
@@ -2234,8 +2226,15 @@ bool EmotiBit::processThermopileData()
 	
 	// Swap buffers with minimal delay to avoid size mismatch
 	unsigned long int swapStart = micros();
+	#ifdef ARDUINO_FEATHER_ESP32 
+	xSemaphoreTake( _xMutex, portMAX_DELAY ); // ToDo: look into implications of portAX_DELAY
+	#endif
 	therm0AMB.swap();
 	therm0Sto.swap();
+	#ifdef ARDUINO_FEATHER_ESP32 
+	xSemaphoreGive( _xMutex );
+	#endif
+
 	unsigned long int swapEnd = micros();
 	//Serial.println("swap: " + String(swapEnd - swapStart));
 	
@@ -2287,7 +2286,13 @@ bool EmotiBit::processThermopileData()
 		// if dummy data was stored
 		if (dataAMB[i] == -2 && dataSto[i] == -2)
 		{
+			#ifdef ARDUINO_FEATHER_ESP32 
+			xSemaphoreTake( _xMutex, portMAX_DELAY ); // ToDo: look into implications of portAX_DELAY
+			#endif
 			dataDoubleBuffers[(uint8_t)EmotiBit::DataType::THERMOPILE]->swap();
+			#ifdef ARDUINO_FEATHER_ESP32
+			xSemaphoreGive( _xMutex );
+			#endif
 			return true;
 			//return dataDoubleBuffers[(uint8_t)EmotiBit::DataType::THERMOPILE]->getData(data, timestamp);
 		}
@@ -2351,7 +2356,13 @@ bool EmotiBit::processThermopileData()
 			therm0Sto.getOverflowCount(DoubleBufferFloat::BufferSelector::OUT)
 		)
 	);
+	#ifdef ARDUINO_FEATHER_ESP32 
+	xSemaphoreTake( _xMutex, portMAX_DELAY ); // ToDo: look into implications of portAX_DELAY
+	#endif
 	dataDoubleBuffers[(uint8_t)EmotiBit::DataType::THERMOPILE]->swap();
+	#ifdef ARDUINO_FEATHER_ESP32 
+	xSemaphoreGive( _xMutex );
+	#endif
 	// ToDo: implement logic to determine return val
 	return true;
 }
@@ -2945,7 +2956,7 @@ void EmotiBit::readSensors()
 #ifdef DEBUG_GET_DATA
 	Serial.println("readSensors()");
 #endif // DEBUG
-	if (DIGITAL_WRITE_DEBUG) digitalWrite(DEBUG_OUT_PIN_0, HIGH);
+	
 
 	static unsigned long readSensorsBegin = micros();
 	if (_debugMode)
@@ -3225,7 +3236,7 @@ void EmotiBit::readSensors()
 	}
 	if (acquireData.debug) pushData(EmotiBit::DataType::DEBUG, micros() - readSensorsBegin); // Add readSensors processing duration to debugBuffer
 
-	if (DIGITAL_WRITE_DEBUG) digitalWrite(DEBUG_OUT_PIN_0, LOW);
+	
 }
 
 void EmotiBit::processHeartRate()
@@ -3330,7 +3341,13 @@ void EmotiBit::processData()
 			}
 			else
 			{
+				#ifdef ARDUINO_FEATHER_ESP32 
+				xSemaphoreTake( _xMutex, portMAX_DELAY ); // ToDo: look into implications of portAX_DELAY
+				#endif
 				dataDoubleBuffers[t]->swap();
+				#ifdef ARDUINO_FEATHER_ESP32
+				xSemaphoreGive( _xMutex );
+				#endif
 				//Serial.print(String(t) + ",");
 			}
 		}
@@ -4404,17 +4421,27 @@ void attachToInterruptTC3(void(*readFunction)(void), EmotiBit* e)
 }
 
 #elif defined ARDUINO_FEATHER_ESP32
-void onTimer() {
-	vTaskResume(EmotiBitDataAcquisition);
-}
-#endif
 
-#ifdef ARDUINO_FEATHER_ESP32
+void attachUpdateToCore(void(*readFunction)(void*))
+{
+	// Creating a new task to run emotibit.update()
+	// Task runs on core 0, along with WiFi tasks.
+	xTaskCreatePinnedToCore(
+		*readFunction,   /* Task function. */
+		"EmotiBitDataProcess",     /* name of task. */
+		32000,       /* Stack size of task */
+		NULL,        /* parameter of the task */
+		1,           /* priority of the task */
+		NULL,      /* Task handle to keep track of created task */
+		0);          /* pin task to core 0 */
+	delay(500);
+}
 
-void attachToCore(void(*readFunction)(void*), EmotiBit*e)
+void attachReadSensorsToCore(void(*readFunction)(void*), EmotiBit*e)
 {
 	attachEmotiBit(e);
-	// assigning readSensors to second core
+	// Creating a new task to run data acquisition
+	// Task runs on core 1, along with main loop.
 	xTaskCreatePinnedToCore(
 		*readFunction,   /* Task function. */
 		"EmotiBitDataAcquisition",     /* name of task. */
@@ -4422,7 +4449,7 @@ void attachToCore(void(*readFunction)(void*), EmotiBit*e)
 		NULL,        /* parameter of the task */
 		configMAX_PRIORITIES - 1,           /* priority of the task */
 		&EmotiBitDataAcquisition,      /* Task handle to keep track of created task */
-		1);          /* pin task to core 0 */
+		1);          /* pin task to core 1 */
 	delay(500);
 }
 
@@ -4442,21 +4469,73 @@ void ReadSensors()
 	}
 }
 #elif defined ARDUINO_FEATHER_ESP32
-void ReadSensors(void *pvParameters)
+void Update(void *pvParameter)
 {
-	Serial.print("The data acquisition is executing on core: "); Serial.println(xPortGetCoreID());
-	while (1) // the function assigned to the second core should never return
+	Serial.print("Update is executing on core: "); Serial.println(xPortGetCoreID());
+	while(1)
 	{
 		if (myEmotiBit != nullptr)
 		{
-			myEmotiBit->readSensors();
-
+			myEmotiBit->update();
 		}
 		else
 		{
 			Serial.println("EmotiBit is nullptr");
 		}
-		vTaskSuspend(NULL);
+		vTaskDelay(pdMS_TO_TICKS(1));  // Delay added to give time to IDLE task
+	}
+}
+
+void ReadSensors(void *pvParameters)
+{
+	Serial.print("The data acquisition is executing on core: "); Serial.println(xPortGetCoreID());
+	int BASE_TIME_PERIOD = (int)((float) 1000000 / (float) BASE_SAMPLING_FREQ);
+	uint32_t timeLast = micros();
+	while (1) // the function should never return, otherwise causes an exception in RTOS
+	{
+		if(micros() - timeLast > BASE_TIME_PERIOD)
+		{
+			timeLast = micros();
+			if (myEmotiBit != nullptr)
+			{
+				xSemaphoreTake( _xMutex, portMAX_DELAY ); // ToDo: look into implications of portAX_DELAY
+				if (myEmotiBit->DIGITAL_WRITE_DEBUG) digitalWrite(myEmotiBit->DEBUG_OUT_PIN_0, HIGH);
+				myEmotiBit->readSensors();
+				if (myEmotiBit->DIGITAL_WRITE_DEBUG) digitalWrite(myEmotiBit->DEBUG_OUT_PIN_0, LOW);
+				xSemaphoreGive( _xMutex );
+			}
+			else
+			{
+				Serial.println("EmotiBit is nullptr");
+			}
+
+			if(myEmotiBit->_freeToSleep && myEmotiBit->_emotiBitWiFi._wifiOff)
+			{
+				int sleepTime;
+				// ToDo: get more accurate buffer time
+				uint32_t wakeupTimebuffer = 600; // in uS. Empirically derived estimate. Time taken by CPU to wake up
+				// ToDo: move this into a calculateSleepTime() function
+				if((timeLast + BASE_TIME_PERIOD) - micros() > wakeupTimebuffer) 
+				{
+					// calculate time to sleep
+					sleepTime = (int)(timeLast + BASE_TIME_PERIOD) - (int)micros() - (int)wakeupTimebuffer;
+				} 
+
+				if(sleepTime > wakeupTimebuffer)
+				{
+					// only sleep if we can wake up in time
+					esp_sleep_enable_timer_wakeup(sleepTime); // every 6.6mS to maintain 150Hz base sampling
+					esp_light_sleep_start(); // start light sleep
+				}
+			}
+			else
+			{
+				// ToDo: Schedule time give to idle task.
+				vTaskDelay(pdMS_TO_TICKS(1));  // if not sleeping, give time-slice to IDLE task
+			}
+
+		}
+		
 	}
 
 }
diff --git a/EmotiBit.h b/EmotiBit.h
index b3052220..ace6832b 100644
--- a/EmotiBit.h
+++ b/EmotiBit.h
@@ -50,14 +50,14 @@ class EmotiBit {
 
 
 
-  String firmware_version = "1.9.0";
+  String firmware_version = "1.9.0.feat-2Core.4";
 
 
 
 	TestingMode testingMode = TestingMode::NONE;
-	const bool DIGITAL_WRITE_DEBUG = false;
+	const bool DIGITAL_WRITE_DEBUG = true;
 #if defined (ARDUINO_FEATHER_ESP32)
-	const uint8_t DEBUG_OUT_PIN_0 = 26;
+	const uint8_t DEBUG_OUT_PIN_0 = 21;
 	const uint8_t DEBUG_OUT_PIN_1 = 33;
 	const uint8_t DEBUG_OUT_PIN_2 = 15;
 #elif defined (ADAFRUIT_FEATHER_M0)
@@ -425,6 +425,8 @@ class EmotiBit {
 	DataType _serialData = DataType::length;
 	volatile bool buttonPressed = false;
 	bool startBufferOverflowTest = false;
+	bool _freeToSleep = false;
+	
 
 	void setupFailed(const String failureMode, int buttonPin = -1);
 	bool setupSdCard();
@@ -673,6 +675,7 @@ class EmotiBit {
 
 	const uint8_t SCOPE_TEST_PIN = A0;
 	bool scopeTestPinOn = false;
+	
 
 };
 
@@ -681,9 +684,10 @@ void attachEmotiBit(EmotiBit*e = nullptr);
 void attachToInterruptTC3(void(*readFunction)(void), EmotiBit*e = nullptr);
 void ReadSensors();
 #elif defined ARDUINO_FEATHER_ESP32
-void onTimer();
-void attachToCore(void(*readFunction)(void*), EmotiBit*e = nullptr);
+void attachReadSensorsToCore(void(*readFunction)(void*), EmotiBit*e = nullptr);
 void ReadSensors(void* pvParameters);
+void Update(void* pvParameters);
+void attachUpdateToCore(void(*readFunction)(void*));
 #endif
 
 
diff --git a/EmotiBit_stock_firmware/EmotiBit_stock_firmware.ino b/EmotiBit_stock_firmware/EmotiBit_stock_firmware.ino
index c9fbebe0..09dbe51b 100644
--- a/EmotiBit_stock_firmware/EmotiBit_stock_firmware.ino
+++ b/EmotiBit_stock_firmware/EmotiBit_stock_firmware.ino
@@ -51,9 +51,13 @@ void setup()
 
 void loop()
 {
-	//Serial.println("emotibit.update()");
-	emotibit.update();
-
+	// Main loop is attached to a different task spawned by default. In our current scheme, 
+	// main loop runs run when acquisitoin task pasuses by calling vTaskDelay()
+	
+	// The update function has been moved to its separate task.
+	//emotibit.update(); 
+	
+	// ToDo: assess time slice given to this task once ported to 2-core 2-task architecture
 	size_t dataAvailable = emotibit.readData(EmotiBit::DataType::PPG_GREEN, &data[0], dataSize);
 	if (dataAvailable > 0)
 	{
@@ -70,4 +74,5 @@ void loop()
 			}
 		}
 	}
+	
 }
\ No newline at end of file
diff --git a/testing/GpioInterruptLogger/GpioInterruptLogger.ino b/testing/GpioInterruptLogger/GpioInterruptLogger.ino
new file mode 100644
index 00000000..9044e679
--- /dev/null
+++ b/testing/GpioInterruptLogger/GpioInterruptLogger.ino
@@ -0,0 +1,144 @@
+/**
+ * @file GpioInterruptLogger
+ *
+ * @section description Description
+ * This example can be used to generate timestamps for external events.
+ * A timestamp in mS and uS is generated everytime an interrupt is triggered.
+ *
+ * @section circuit Circuit
+ * - This is written for Feather M0. Tested on Adafruit Feather M0.
+ * - Refer adafruit's documentation on pin details: https://learn.adafruit.com/adafruit-feather-m0-wifi-atwinc1500/pinouts
+ * - Use PIN_IN_1 and PIN_IN_2 as inputs to which external interrupt signals can be attached.
+ * - PIN_OUT_1 and PIN_OUT_2 toggle at half the frequeny input pins, respectively. (Useful if probing with an Digital Oscilloscope) 
+ * 
+ * @section author Author
+ * - Created by Nitin Nair for EmotiBit.
+ * 
+ */
+
+
+// ToDO: fix for Feather ESP32. Looks like the double buffer implementation is crashing for ESP32.
+//#define DEBUG_SERIAL
+#ifdef ARDUINO_FEATHER_ESP32
+#define PIN_IN_1 5
+#define PIN_OUT_1 18
+#elif defined ADAFRUIT_FEATHER_M0
+#define PIN_IN_1 24
+#define PIN_OUT_1 23
+#define PIN_IN_2 22
+#define PIN_OUT_2 5
+#endif
+#include <DoubleBufferFloat.h>
+#include <String.h>
+
+DoubleBufferFloat us_timeBuffer_IN1(50);
+DoubleBufferFloat ms_timeBuffer_IN1(50);
+DoubleBufferFloat us_timeBuffer_IN2(50);
+DoubleBufferFloat ms_timeBuffer_IN2(50);
+#ifdef ARDUINO_FEATHER_ESP32
+void IRAM_ATTR isr_pin1() {
+	//counter++;
+  // push to Double Buffer
+  us_timeBuffer_IN1.push_back(micros());
+  ms_timeBuffer_IN1.push_back(millis());
+  digitalWrite(PIN_OUT_1, !digitalRead(PIN_OUT_1));  // toggle a pin everytime we get a rising edge. Half the freq of PIN_IN_1
+
+  // ToDo: implement logic for pin 2
+}
+#elif defined ADAFRUIT_FEATHER_M0
+void isr_pin1() {
+	//counter++;
+  // push to Double Buffer
+  us_timeBuffer_IN1.push_back(micros());
+  ms_timeBuffer_IN1.push_back(millis());
+  digitalWrite(PIN_OUT_1, !digitalRead(PIN_OUT_1));  // toggle a pin everytime we get a rising edge. Half the freq of PIN_IN_1
+}
+
+void isr_pin2() {
+	//counter++;
+  // push to Double Buffer
+  us_timeBuffer_IN2.push_back(micros());
+  ms_timeBuffer_IN2.push_back(millis());
+  digitalWrite(PIN_OUT_2, !digitalRead(PIN_OUT_2));  // toggle a pin everytime we get a rising edge. Half the freq of PIN_IN_2
+}
+#endif
+
+
+void getData(DoubleBufferFloat *buf_us, DoubleBufferFloat *buf_ms, String pin)
+{
+  float *us_timeData; float *ms_timeData;
+  uint32_t tu, tm; // dummy variables.
+  size_t dataAvailableuS, dataAvailablemS;
+  // get the data
+  #ifdef DEBUG_SERIAL
+  Serial.println("getting data");
+  #endif
+  dataAvailableuS = buf_us->getData(&us_timeData, &tu, false);
+  dataAvailablemS = buf_ms->getData(&ms_timeData, &tm, false);
+  #ifdef DEBUG_SERIAL
+  Serial.println("got data");
+  #endif
+  if(dataAvailableuS == dataAvailablemS)
+  {
+    #ifdef DEBUG_SERIAL
+    Serial.print("dataAvailableuS"); Serial.println(dataAvailableuS);
+    #endif
+    for (uint8_t i = 0; i < dataAvailableuS; i++) 
+    {
+      // ToDo: improve serial output pattern.
+      String str = pin + ":" + String(ms_timeData[i]) + ":" + String(us_timeData[i])  ;
+      Serial.println(str); 
+    }
+  }
+  else
+  {
+    Serial.print("dataAvailableuS: "); Serial.println(dataAvailableuS);
+    Serial.print("dataAvailablemS: "); Serial.println(dataAvailablemS);
+    Serial.println("mismatch in buffer lengths");
+  }
+}
+void setup() {
+	Serial.begin(2000000);
+	pinMode(PIN_IN_1, INPUT);
+  pinMode(PIN_OUT_1, OUTPUT);
+	pinMode(PIN_IN_2, INPUT);
+  pinMode(PIN_OUT_2, OUTPUT);
+  #ifdef ARDUINO_FEATHER_ESP32
+	attachInterrupt(PIN_IN_1, isr_pin1, RISING);
+  #elif defined ADAFRUIT_FEATHER_M0
+  attachInterrupt( digitalPinToInterrupt( PIN_IN_1 ), isr_pin1, RISING );
+  attachInterrupt( digitalPinToInterrupt( PIN_IN_2 ), isr_pin2, RISING );
+  #endif
+}
+
+void loop() {
+  uint32_t timeNow = millis();
+
+  while(1)
+  {
+    if(millis() - timeNow > 100)
+    {
+      #ifdef DEBUG_SERIAL
+      Serial.println("timeNow > millis()");
+      #endif
+      timeNow = millis();
+      #ifdef DEBUG_SERIAL
+      Serial.println("swapping buffer");
+      #endif
+      us_timeBuffer_IN1.swap(); // swap buffers before reading
+      ms_timeBuffer_IN1.swap(); // swap buffers before reading
+      us_timeBuffer_IN2.swap(); // swap buffers before reading
+      ms_timeBuffer_IN2.swap(); // swap buffers before reading
+      #ifdef DEBUG_SERIAL
+      Serial.println("swapped buffer");
+      #endif
+      getData(&us_timeBuffer_IN1, &ms_timeBuffer_IN1, String("PIN_1"));
+      getData(&us_timeBuffer_IN2, &ms_timeBuffer_IN2, String("PIN_2"));
+      
+    }
+    else
+    {
+      // do ntohing
+    }
+  }
+}
\ No newline at end of file
diff --git a/testing/InterruptBasedGpioToggle/InterruptBasedGpioToggle.ino b/testing/InterruptBasedGpioToggle/InterruptBasedGpioToggle.ino
new file mode 100644
index 00000000..7d32d972
--- /dev/null
+++ b/testing/InterruptBasedGpioToggle/InterruptBasedGpioToggle.ino
@@ -0,0 +1,33 @@
+/**
+ * @file InterruptBasedGpioToggle
+ *
+ * @section description Description
+ * This example toggles a GPIO using hw timer.
+ * Creates a sq waveform to test timing accuracy.
+ * This example was created to test the GpioInterruptLogger example.
+ *
+ * @section circuit Circuit
+ * - This is written for ESP32. Tested on Adafruit Feather ESP32 Huzzah.
+ * - Pin 5 generates the timer output. Refer Adafruit Pinout for pin location and details: https://learn.adafruit.com/assets/111179
+ * 
+ * @section author Author
+ * - Created by Nitin Nair for EmotiBit.
+ * 
+ */
+ 
+#define OUT_PIN 5
+hw_timer_t *My_timer = NULL;
+void IRAM_ATTR onTimer(){
+digitalWrite(OUT_PIN, !digitalRead(OUT_PIN));
+}
+void setup() {
+pinMode(OUT_PIN, OUTPUT);
+My_timer = timerBegin(0, 80, true);
+timerAttachInterrupt(My_timer, &onTimer, true);
+// We want to create a wave with a time period of 6666uS (150Hz, default data acuisition task frequency)
+// Choose timer to be 1/2 of required time period
+timerAlarmWrite(My_timer, 3333, true); 
+timerAlarmEnable(My_timer); //Just Enable
+}
+void loop() {
+}
\ No newline at end of file