diff --git a/usb/device/targets/TARGET_NORDIC/TARGET_MCU_NRF52840/USBPhyHw.h b/usb/device/targets/TARGET_NORDIC/TARGET_MCU_NRF52840/USBPhyHw.h
index 1e62ab146e..75e5ea6f33 100644
--- a/usb/device/targets/TARGET_NORDIC/TARGET_MCU_NRF52840/USBPhyHw.h
+++ b/usb/device/targets/TARGET_NORDIC/TARGET_MCU_NRF52840/USBPhyHw.h
@@ -68,6 +68,7 @@ private:
     USBPhyEvents *events;
 
     bool sof_enabled;
+    bool connect_enabled;
 
     typedef enum usb_hw_event_type_t {
     	USB_HW_EVENT_NONE  = 0,
@@ -96,6 +97,11 @@ private:
     // Returns the corresponding enumeration given an mbed endpoint number
     static nrf_drv_usbd_ep_t get_nordic_endpoint(usb_ep_t endpoint);
 
+    void _reset(void);
+
+    static void enable_usb_interrupts(void);
+    static void disable_usb_interrupts(void);
+
 };
 
 #endif
diff --git a/usb/device/targets/TARGET_NORDIC/TARGET_MCU_NRF52840/USBPhy_Nordic.cpp b/usb/device/targets/TARGET_NORDIC/TARGET_MCU_NRF52840/USBPhy_Nordic.cpp
index a383c2a209..0d3816e9bd 100644
--- a/usb/device/targets/TARGET_NORDIC/TARGET_MCU_NRF52840/USBPhy_Nordic.cpp
+++ b/usb/device/targets/TARGET_NORDIC/TARGET_MCU_NRF52840/USBPhy_Nordic.cpp
@@ -26,21 +26,32 @@
 #define IS_IN_EP(ep) 	(ep & 0x80)  // Checks if the given endpoint is an IN endpoint (MSB set)
 #define IS_OUT_EP(ep) 	(ep & ~0x80) // Checks if the given endpoint is an OUT endpoint (MSB clear)
 
+// Debugging flag for tracking USB events
+#define USBD_DEBUG 1
+
 // Nordic USBD driver IRQ handler
 extern "C" void USBD_IRQHandler(void);
 
-static USBPhyHw *instance;
+static USBPhyHw *instance = 0;
 
 static void usbd_event_handler(nrf_drv_usbd_evt_t const * const p_event);
 static void power_usb_event_handler(nrf_drv_power_usb_evt_t event);
 
+#if USBD_DEBUG
+
+// Static array of saved events to track what happens
+static nrf_drv_usbd_evt_t debug_events[32];
+static uint8_t debug_evt_index = 0;
+
+#endif
+
 USBPhy *get_usb_phy() {
 	static USBPhyHw usbphy;
 	return &usbphy;
 }
 
 USBPhyHw::USBPhyHw() :
-		events(NULL), sof_enabled(false),
+		events(NULL), sof_enabled(false), connect_enabled(false),
 		usb_event_type(USB_HW_EVENT_NONE),
 		usb_power_event(NRF_DRV_POWER_USB_EVT_REMOVED) {
 
@@ -77,11 +88,12 @@ void USBPhyHw::init(USBPhyEvents *events) {
 	ret = nrf_drv_usbd_init(usbd_event_handler);
 	APP_ERROR_CHECK(ret);
 
+	// Store a reference to this instance
 	instance = this;
 
 	// Enable IRQ
 	NVIC_SetVector(USBD_IRQn, (uint32_t)USBD_IRQHandler);
-	NVIC_SetPriority(USBD_IRQn, 6);
+	NVIC_SetPriority(USBD_IRQn, 7);
 	NVIC_EnableIRQ(USBD_IRQn);
 }
 
@@ -91,7 +103,10 @@ void USBPhyHw::deinit() {
 	// Disable the USB Device driver
 	ret_code_t ret = nrf_drv_usbd_uninit();
 	APP_ERROR_CHECK(ret);
-	//NVIC_DisableIRQ(USBD_IRQn);
+	NVIC_DisableIRQ(USBD_IRQn);
+
+	// Clear the instance pointer?
+	//instance = 0;
 }
 
 bool USBPhyHw::powered() {
@@ -104,13 +119,27 @@ bool USBPhyHw::powered() {
 
 void USBPhyHw::connect() {
 
-	/*if(!nrf_drv_usbd_is_enabled())
-		nrf_drv_usbd_enable();
-	if(!nrf_drv_usbd_is_started())
-		nrf_drv_usbd_start(true);*/
+	// To save power, we only enable the USBD peripheral
+	// when there's actually VBUS detected
+
+	// So flag that the USB stack is ready to connect
+	this->connect_enabled = true;
+
+	// If VBUS is already available, enable immediately
+	if(nrf_drv_power_usbstatus_get() == NRF_DRV_POWER_USB_STATE_CONNECTED)
+	{
+		// Enabling USB will cause NRF_DRV_POWER_USB_EVT_READY
+		// to occur, which will start the USBD peripheral
+		// when the internal regulator has settled
+		if(!nrf_drv_usbd_is_enabled())
+			nrf_drv_usbd_enable();
+	}
 }
 
 void USBPhyHw::disconnect() {
+
+	this->connect_enabled = false;
+
 	if(nrf_drv_usbd_is_started())
 		nrf_drv_usbd_stop();
 	if(nrf_drv_usbd_is_enabled())
@@ -268,6 +297,15 @@ void USBPhyHw::process() {
 	if (usb_event_type == USB_HW_EVENT_NONE)
 		return;
 	else if (usb_event_type == USB_HW_EVENT_USBD) {
+
+#ifdef USBD_DEBUG
+		// Save this event to the static log
+		memcpy(&debug_events[debug_evt_index++], &usb_event, sizeof(nrf_drv_usbd_evt_t));
+		// Reset index if we overflow the buffer
+		if(debug_evt_index >= 32)
+			debug_evt_index = 0;
+#endif
+
 		// Process regular USBD events
 		switch (usb_event.type) {
 		case NRF_DRV_USBD_EVT_SUSPEND:
@@ -279,6 +317,7 @@ void USBPhyHw::process() {
 		case NRF_DRV_USBD_EVT_WUREQ:
 			break;
 		case NRF_DRV_USBD_EVT_RESET:
+			this->_reset();
 			events->reset();
 			break;
 		case NRF_DRV_USBD_EVT_SOF:
@@ -298,13 +337,29 @@ void USBPhyHw::process() {
 				else
 				{
 					if((usb_event.data.eptransfer.ep & 0x7F) == 0)
+					{
+						/* NOTE: Data values or size may be tested here to decide if clear or stall.
+						 * If errata 154 is present the data transfer is acknowledged by the hardware. */
+						if (!nrf_drv_usbd_errata_154()) {
+							/* Transfer ok - allow status stage */
+							nrf_drv_usbd_setup_clear();
+						}
+
 						events->ep0_out();
+					}
 					else
 						events->out((usb_ep_t) usb_event.data.eptransfer.ep);
 				}
 			}
 			break;
 		case NRF_DRV_USBD_EVT_SETUP: {
+
+			// Clear endpoint 0 stalls on setup packet receive
+			if(nrf_drv_usbd_ep_stall_check(NRF_DRV_USBD_EPOUT0))
+				nrf_drv_usbd_ep_stall_clear(NRF_DRV_USBD_EPOUT0);
+			if(nrf_drv_usbd_ep_stall_check(NRF_DRV_USBD_EPIN0))
+				nrf_drv_usbd_ep_stall_clear(NRF_DRV_USBD_EPIN0);
+
 			// Copy the setup packet into the internal buffer
 			nrf_drv_usbd_setup_get(&setup_buf);
 			events->ep0_setup();
@@ -313,9 +368,6 @@ void USBPhyHw::process() {
 		default:
 			break;
 
-			// Re-enable interrupt
-			//NVIC_ClearPendingIRQ(USB_IRQn);
-			//NVIC_EnableIRQ(USB_IRQn);
 		}
 	}
 	else if (usb_event_type == USB_HW_EVENT_POWER)
@@ -323,16 +375,20 @@ void USBPhyHw::process() {
 		// Process USB power-related events
 		switch (usb_power_event) {
 		case NRF_DRV_POWER_USB_EVT_DETECTED:
-			if(!nrf_drv_usbd_is_enabled())
-				nrf_drv_usbd_enable();
-			events->power(true);
+			if(this->connect_enabled) {
+				if(!nrf_drv_usbd_is_enabled())
+					nrf_drv_usbd_enable();
+				events->power(true);
+			}
 			break;
 		case NRF_DRV_POWER_USB_EVT_REMOVED:
 			events->power(false);
 			break;
 		case NRF_DRV_POWER_USB_EVT_READY:
-			if(!nrf_drv_usbd_is_started())
-				nrf_drv_usbd_start(true);
+			if(this->connect_enabled) {
+				if(!nrf_drv_usbd_is_started())
+					nrf_drv_usbd_start(false);//nrf_drv_usbd_start(true);
+			}
 			break;
 		default:
 			ASSERT(false);
@@ -342,10 +398,14 @@ void USBPhyHw::process() {
 	// Unflag the event type
 	usb_event_type = USB_HW_EVENT_NONE;
 
+	// Re-enable interrupt
+	NVIC_ClearPendingIRQ(USBD_IRQn);
+	enable_usb_interrupts();
 }
 
 void USBPhyHw::_usb_event_handler(
 		nrf_drv_usbd_evt_t const * const p_event) {
+	disable_usb_interrupts();
 	// Copy the event data into internal memory
 	memcpy(&instance->usb_event, p_event, sizeof(instance->usb_event));
 	// Tell the upper layers of the stack to process the event
@@ -354,6 +414,7 @@ void USBPhyHw::_usb_event_handler(
 }
 
 void USBPhyHw::_usb_power_event_handler(nrf_drv_power_usb_evt_t event) {
+	disable_usb_interrupts();
 	// Copy the event data into internal memory
 	instance->usb_power_event = event;
 	// Tell the upper layers of the stack to process the event
@@ -374,16 +435,70 @@ nrf_drv_usbd_ep_t USBPhyHw::get_nordic_endpoint(usb_ep_t endpoint) {
 	return (nrf_drv_usbd_ep_t) endpoint;
 }
 
+void USBPhyHw::_reset(void)
+{
+	// Disable all endpoints except for control endpoints
+	nrf_drv_usbd_ep_default_config();
+
+	// TODO - Clear all endpoint interrupts?
+}
+
+void USBPhyHw::enable_usb_interrupts(void) {
+	// Enable USB and USB-related power interrupts
+	NVIC_EnableIRQ(USBD_IRQn);
+	nrf_power_int_enable(NRF_POWER_INT_USBDETECTED_MASK |
+						 NRF_POWER_INT_USBREMOVED_MASK |
+						 NRF_POWER_INT_USBPWRRDY_MASK);
+}
+
+void USBPhyHw::disable_usb_interrupts(void) {
+	// Disable USB and USB-related power interrupts
+	NVIC_DisableIRQ(USBD_IRQn);
+	nrf_power_int_disable(NRF_POWER_INT_USBDETECTED_MASK |
+						 NRF_POWER_INT_USBREMOVED_MASK |
+						 NRF_POWER_INT_USBPWRRDY_MASK);
+}
+
 static void power_usb_event_handler(nrf_drv_power_usb_evt_t event) {
-	// Pass the event on to the USBPhyHW instance
-	instance->_usb_power_event_handler(event);
+	if(instance) {
+		// Pass the event on to the USBPhyHW instance
+		instance->_usb_power_event_handler(event);
+	}
 }
 
 static void usbd_event_handler(nrf_drv_usbd_evt_t const * const p_event) {
-	// Pass the event on to the USBPhyHW instance
-	instance->_usb_event_handler(p_event);
+	if(instance) {
+		NVIC_DisableIRQ(USBD_IRQn);
+		// Pass the event on to the USBPhyHW instance
+		instance->_usb_event_handler(p_event);
+	}
 }
 
 extern "C" {
-void USBD_IRQHandler_v(void) { }
+
+	/**
+	 * @brief Feeder passing data between mbed and nordic USB stacks
+	 *
+	 * @param[out]    p_next    See @ref nrf_drv_usbd_feeder_t documentation.
+	 * @param[in,out] p_context See @ref nrf_drv_usbd_feeder_t documentation.
+	 * @param[in]     ep_size   See @ref nrf_drv_usbd_feeder_t documentation.
+	 *
+	 * @retval true  Continue transfer.
+	 * @retval false This was the last transfer.
+	 */
+	bool mbed_nrf_feeder(nrf_drv_usbd_ep_transfer_t * p_next,
+								void * p_context,
+								size_t ep_size)
+	{
+
+
+		// We don't know if this is the last transfer or not at this level -- mbed doesn't tell us...
+		// So just tell the nordic layer that the transfer isn't over yet (so don't NAK/STALL)
+		return true;
+	}
+
 }
+
+//extern "C" {
+//void USBD_IRQHandler_v(void) { }
+//}