add Serial.attachInterrupt_Send()

Author: gicking

Diff for: cores/arduino/HardwareSerial.cpp

@@ -120,6 +120,7 @@ void HardwareSerial::_tx_complete_irq(void)
   if (_isrTx) {
     _isrTx();
   }
+
 }
 
 // Public Methods //////////////////////////////////////////////////////////////

Diff for: cores/arduino/HardwareSerial2.cpp

@@ -37,22 +37,13 @@
 
 #if defined(HAVE_HWSERIAL2)
 
-// xxx
-extern int count;
-
 ISR(USART2_RX_vect)
 {
   Serial2._rx_complete_irq();
 }
 
 ISR(USART2_UDRE_vect)
 {
-  // xxx
-  Serial.println(++count);
-  digitalWrite(LED_BUILTIN, HIGH);
-  delayMicroseconds(50);
-  digitalWrite(LED_BUILTIN, LOW);
-
   Serial2._tx_udr_empty_irq();
 }