diff --git a/cores/arduino/USB/CDC.cpp b/cores/arduino/USB/CDC.cpp
index b7332a82..ffae21b8 100644
--- a/cores/arduino/USB/CDC.cpp
+++ b/cores/arduino/USB/CDC.cpp
@@ -176,13 +176,10 @@ int Serial_::peek(void)
 
 int Serial_::read(void)
 {
-	ring_buffer *buffer = &cdc_rx_buffer;
-
-	// if the head isn't ahead of the tail, we don't have any characters
-	if (buffer->head == buffer->tail && !buffer->full)
-	{
-		if (usb.available(CDC_ENDPOINT_OUT))
-			accept();
+	if (_serialPeek != -1) {
+		int res = _serialPeek;
+		_serialPeek = -1;
+		return res;
 	}
 	return usb.recv(CDC_ENDPOINT_OUT);
 }
diff --git a/cores/arduino/USB/USBCore.cpp b/cores/arduino/USB/USBCore.cpp
index efa614f9..f86f8568 100644
--- a/cores/arduino/USB/USBCore.cpp
+++ b/cores/arduino/USB/USBCore.cpp
@@ -292,15 +292,6 @@ void USBDeviceClass::standby() {
 void USBDeviceClass::handleEndpoint(uint8_t ep)
 {
 #if defined(CDC_ENABLED)
-	if (ep == CDC_ENDPOINT_OUT)
-	{
-		// The RAM Buffer is empty: we can receive data
-		//usbd.epBank0ResetReady(CDC_ENDPOINT_OUT);
-
-		// Handle received bytes
-		if (available(CDC_ENDPOINT_OUT))
-			Serial.accept();
-	}
 	if (ep == CDC_ENDPOINT_IN)
 	{
 		// NAK on endpoint IN, the bank is not yet filled in.
diff --git a/cores/arduino/WInterrupts.c b/cores/arduino/WInterrupts.c
index 3a9aa36d..539c83ff 100644
--- a/cores/arduino/WInterrupts.c
+++ b/cores/arduino/WInterrupts.c
@@ -102,6 +102,7 @@ void attachInterrupt(uint32_t pin, voidFuncPtr callback, uint32_t mode)
     // Store interrupts to service in order of when they were attached
     // to allow for first come first serve handler
     uint32_t current = 0;
+    uint32_t inMask = (1UL << in);
 
     // Check if we already have this interrupt
     for (current=0; current<nints; current++) {
@@ -128,10 +129,6 @@ void attachInterrupt(uint32_t pin, voidFuncPtr callback, uint32_t mode)
         EIC->NMICTRL.bit.NMISENSE = EIC_NMICTRL_NMISENSE_HIGH;
         break;
 
-      case CHANGE:
-        EIC->CONFIG[config].reg |= EIC_CONFIG_SENSE0_BOTH_Val << pos;
-        break;
-
       case CHANGE:
         EIC->NMICTRL.bit.NMISENSE = EIC_NMICTRL_NMISENSE_BOTH;
         break;
@@ -146,7 +143,7 @@ void attachInterrupt(uint32_t pin, voidFuncPtr callback, uint32_t mode)
     }
 
     // Assign callback to interrupt
-    callbacksInt[EXTERNAL_INT_NMI] = callback;
+    ISRcallback[EXTERNAL_INT_NMI] = callback;
 
   } else { // Not NMI, is external interrupt
 
@@ -161,7 +158,7 @@ void attachInterrupt(uint32_t pin, voidFuncPtr callback, uint32_t mode)
     pinPeripheral(pin, PIO_EXTINT);
 
     // Assign callback to interrupt
-    callbacksInt[in] = callback;
+    ISRcallback[in] = callback;
 
     // Look for right CONFIG register to be addressed
     if (in > EXTERNAL_INT_7) {
@@ -208,7 +205,6 @@ void attachInterrupt(uint32_t pin, voidFuncPtr callback, uint32_t mode)
   EIC->CTRLA.bit.ENABLE = 1;
   while (EIC->SYNCBUSY.bit.ENABLE == 1) { }
 #endif
-  }
 }
 
 /*
@@ -240,7 +236,7 @@ void detachInterrupt(uint32_t pin)
   // Remove callback from the ISR list
   uint32_t current;
   for (current=0; current<nints; current++) {
-    if (ISRlist[current] == inMask) {
+    if (ISRlist[current] == (1UL << in)) {
       break;
     }
   }
@@ -263,8 +259,8 @@ void InterruptHandler(uint32_t i)
   if ((EIC->INTFLAG.reg & (1 << i)) != 0)
   {
     // Call the callback function if assigned
-    if (callbacksInt[i]) {
-      callbacksInt[i]();
+    if (ISRcallback[i]) {
+      ISRcallback[i]();
     }
 
     // Clear the interrupt
@@ -376,6 +372,7 @@ void EIC_Handler(void)
  */
 void NMI_Handler(void)
 {
-  if (callbacksInt[EXTERNAL_INT_NMI]) callbacksInt[EXTERNAL_INT_NMI]();
+  if (ISRcallback[EXTERNAL_INT_NMI]) ISRcallback[EXTERNAL_INT_NMI]();
   EIC->NMIFLAG.bit.NMI = 1; // Clear interrupt
 }
+#endif
\ No newline at end of file
diff --git a/platform.txt b/platform.txt
index 27438209..2cee5ab9 100644
--- a/platform.txt
+++ b/platform.txt
@@ -185,4 +185,4 @@ tools.openocd-withbootsize.erase.pattern=
 
 tools.openocd-withbootsize.bootloader.params.verbose=-d2
 tools.openocd-withbootsize.bootloader.params.quiet=-d0
-tools.openocd-withbootsize.bootloader.pattern="{path}/{cmd}" {bootloader.verbose} -s "{path}/share/openocd/scripts/" -f "{runtime.platform.path}/variants/{build.variant}/{build.openocdscript}" -c "telnet_port disabled; init; halt; at91samd bootloader 0; program {{{runtime.platform.path}/bootloaders/{bootloader.file}}} verify reset; shutdown"
+tools.openocd-withbootsize.bootloader.pattern="{path}/{cmd}" {bootloader.verbose} -s "{path}/share/openocd/scripts/" -f "{runtime.platform.path}/variants/{build.variant}/{build.openocdscript}" -c "telnet_port disabled; init; halt; at91samd bootloader 0; program {{{runtime.platform.path}/bootloaders/{bootloader.file}}} verify reset; shutdown"
\ No newline at end of file