From 291b7f7b8a19c43e267ab01b32fdaa9204b14c70 Mon Sep 17 00:00:00 2001
From: Georg Icking-Konert <icking@onlinehome.de>
Date: Fri, 8 Nov 2019 06:06:04 +0100
Subject: [PATCH 1/8] added optional custom handler to Serial interrupt

added optional custom handler to Serial interrupt. Is minor enhancement
of NeoHWSerial by SlashDevin
(https://github.com/SlashDevin/NeoHWSerial), as user function also gets
UART status as parameter to e.g. detect LIN break in user routine.

Added as core extension instead of library due to similar extension for
Due (https://github.com/gicking/ArduinoCore-sam) which AFAIK cannot be
implemented as library.
---
 cores/arduino/HardwareSerial.cpp       | 10 ++++++
 cores/arduino/HardwareSerial.h         | 11 ++++++
 cores/arduino/HardwareSerial0.cpp      |  2 ++
 cores/arduino/HardwareSerial1.cpp      |  2 ++
 cores/arduino/HardwareSerial2.cpp      |  2 ++
 cores/arduino/HardwareSerial3.cpp      |  2 ++
 cores/arduino/HardwareSerial_private.h | 50 ++++++++++++++++----------
 7 files changed, 61 insertions(+), 18 deletions(-)

diff --git a/cores/arduino/HardwareSerial.cpp b/cores/arduino/HardwareSerial.cpp
index e99d503d8..56eb744fa 100644
--- a/cores/arduino/HardwareSerial.cpp
+++ b/cores/arduino/HardwareSerial.cpp
@@ -20,6 +20,8 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
+  Modified 2 November 2015 by SlashDev
+  Modified 7 November 2019 by Georg Icking-Konert
 */
 
 #include <stdlib.h>
@@ -278,4 +280,12 @@ size_t HardwareSerial::write(uint8_t c)
   return 1;
 }
 
+void HardwareSerial::attachInterrupt( isr_t fn )
+{
+  uint8_t oldSREG = SREG;
+  cli();
+  _isr = fn;
+  SREG = oldSREG;
+}
+
 #endif // whole file
diff --git a/cores/arduino/HardwareSerial.h b/cores/arduino/HardwareSerial.h
index 17000c2cc..1bb395d8a 100644
--- a/cores/arduino/HardwareSerial.h
+++ b/cores/arduino/HardwareSerial.h
@@ -19,6 +19,8 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
+  Modified 2 November 2015 by SlashDev
+  Modified 7 November 2019 by Georg Icking-Konert
 */
 
 #ifndef HardwareSerial_h
@@ -137,6 +139,15 @@ class HardwareSerial : public Stream
     // Interrupt handlers - Not intended to be called externally
     inline void _rx_complete_irq(void);
     void _tx_udr_empty_irq(void);
+
+    typedef void (* isr_t)( uint8_t d=0x00, uint8_t s=0x00 );
+    void attachInterrupt( isr_t fn );
+    void detachInterrupt() { attachInterrupt( (isr_t) NULL ); };
+  private:
+    isr_t  _isr;
+
+    HardwareSerial( const HardwareSerial & );
+    HardwareSerial & operator =( const HardwareSerial &);
 };
 
 #if defined(UBRRH) || defined(UBRR0H)
diff --git a/cores/arduino/HardwareSerial0.cpp b/cores/arduino/HardwareSerial0.cpp
index 1146eebab..ece78a636 100644
--- a/cores/arduino/HardwareSerial0.cpp
+++ b/cores/arduino/HardwareSerial0.cpp
@@ -20,6 +20,8 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
+  Modified 2 November 2015 by SlashDev
+  Modified 7 November 2019 by Georg Icking-Konert
 */
 
 #include "Arduino.h"
diff --git a/cores/arduino/HardwareSerial1.cpp b/cores/arduino/HardwareSerial1.cpp
index 19625e235..c436e1690 100644
--- a/cores/arduino/HardwareSerial1.cpp
+++ b/cores/arduino/HardwareSerial1.cpp
@@ -20,6 +20,8 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
+  Modified 2 November 2015 by SlashDev
+  Modified 7 November 2019 by Georg Icking-Konert
 */
 
 #include "Arduino.h"
diff --git a/cores/arduino/HardwareSerial2.cpp b/cores/arduino/HardwareSerial2.cpp
index fd334ae15..5558b17d1 100644
--- a/cores/arduino/HardwareSerial2.cpp
+++ b/cores/arduino/HardwareSerial2.cpp
@@ -20,6 +20,8 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
+  Modified 2 November 2015 by SlashDev
+  Modified 7 November 2019 by Georg Icking-Konert
 */
 
 #include "Arduino.h"
diff --git a/cores/arduino/HardwareSerial3.cpp b/cores/arduino/HardwareSerial3.cpp
index a68095b37..f6ba55460 100644
--- a/cores/arduino/HardwareSerial3.cpp
+++ b/cores/arduino/HardwareSerial3.cpp
@@ -20,6 +20,8 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
+  Modified 2 November 2015 by SlashDev
+  Modified 7 November 2019 by Georg Icking-Konert
 */
 
 #include "Arduino.h"
diff --git a/cores/arduino/HardwareSerial_private.h b/cores/arduino/HardwareSerial_private.h
index 761a5e559..72a9063b3 100644
--- a/cores/arduino/HardwareSerial_private.h
+++ b/cores/arduino/HardwareSerial_private.h
@@ -19,6 +19,8 @@
   Modified 23 November 2006 by David A. Mellis
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
+  Modified 2 November 2015 by SlashDev
+  Modified 7 November 2019 by Georg Icking-Konert
 */
 
 #include "wiring_private.h"
@@ -92,7 +94,8 @@ HardwareSerial::HardwareSerial(
     _ucsra(ucsra), _ucsrb(ucsrb), _ucsrc(ucsrc),
     _udr(udr),
     _rx_buffer_head(0), _rx_buffer_tail(0),
-    _tx_buffer_head(0), _tx_buffer_tail(0)
+    _tx_buffer_head(0), _tx_buffer_tail(0),
+    _isr(0)
 {
 }
 
@@ -100,24 +103,35 @@ HardwareSerial::HardwareSerial(
 
 void HardwareSerial::_rx_complete_irq(void)
 {
-  if (bit_is_clear(*_ucsra, UPE0)) {
-    // No Parity error, read byte and store it in the buffer if there is
-    // room
-    unsigned char c = *_udr;
-    rx_buffer_index_t i = (unsigned int)(_rx_buffer_head + 1) % SERIAL_RX_BUFFER_SIZE;
+  // user function was attached -> call it with data and status byte 
+  if (_isr) {
+    unsigned char status = *_ucsra;
+    unsigned char data = *_udr;
+    _isr( data, status );
+  }
 
-    // if we should be storing the received character into the location
-    // just before the tail (meaning that the head would advance to the
-    // current location of the tail), we're about to overflow the buffer
-    // and so we don't write the character or advance the head.
-    if (i != _rx_buffer_tail) {
-      _rx_buffer[_rx_buffer_head] = c;
-      _rx_buffer_head = i;
-    }
-  } else {
-    // Parity error, read byte but discard it
-    *_udr;
-  };
+  // default: save data in ring buffer
+  else {  
+    if (bit_is_clear(*_ucsra, UPE0)) {
+      unsigned char c = *_udr;
+      // No Parity error, read byte and store it in the buffer if there is
+      // room
+      rx_buffer_index_t i = (unsigned int)(_rx_buffer_head + 1) % SERIAL_RX_BUFFER_SIZE;
+
+      // if we should be storing the received character into the location
+      // just before the tail (meaning that the head would advance to the
+      // current location of the tail), we're about to overflow the buffer
+      // and so we don't write the character or advance the head.
+      if (i != _rx_buffer_tail) {
+        _rx_buffer[_rx_buffer_head] = c;
+        _rx_buffer_head = i;
+      }
+    } 
+    else {
+      // Parity error, read byte but discard it
+      *_udr;
+    };
+  }
 }
 
 #endif // whole file

From e5fd810fc507217143ad93fe92b70abb9ba73aea Mon Sep 17 00:00:00 2001
From: Georg Icking-Konert <icking@onlinehome.de>
Date: Sat, 9 Nov 2019 18:00:59 +0100
Subject: [PATCH 2/8] fixed compiler warnings

fixed compiler warnings when compiling with max. waring level
---
 cores/arduino/HardwareSerial.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/cores/arduino/HardwareSerial.h b/cores/arduino/HardwareSerial.h
index 1bb395d8a..f8a3bc65b 100644
--- a/cores/arduino/HardwareSerial.h
+++ b/cores/arduino/HardwareSerial.h
@@ -140,7 +140,7 @@ class HardwareSerial : public Stream
     inline void _rx_complete_irq(void);
     void _tx_udr_empty_irq(void);
 
-    typedef void (* isr_t)( uint8_t d=0x00, uint8_t s=0x00 );
+    typedef void (* isr_t)( uint8_t d, uint8_t s );
     void attachInterrupt( isr_t fn );
     void detachInterrupt() { attachInterrupt( (isr_t) NULL ); };
   private:

From 8665c0367d9fddffdfa1777a7cdda0fa6bd8427c Mon Sep 17 00:00:00 2001
From: Georg Icking-Konert <icking@onlinehome.de>
Date: Sun, 17 Nov 2019 09:08:23 +0100
Subject: [PATCH 3/8] add Serial.attachInterrupt_Send()

add Serial.attachInterrupt_Send()
rename Serial.attachInterrupt() to Serial.attachInterrupt_Receive()
---
 cores/arduino/HardwareSerial.cpp       | 31 ++++++++++++++++++++++++--
 cores/arduino/HardwareSerial.h         | 15 ++++++++-----
 cores/arduino/HardwareSerial0.cpp      | 16 +++++++++++--
 cores/arduino/HardwareSerial1.cpp      | 14 ++++++++++--
 cores/arduino/HardwareSerial2.cpp      | 17 ++++++++++++--
 cores/arduino/HardwareSerial3.cpp      |  8 +++++--
 cores/arduino/HardwareSerial_private.h | 10 ++++-----
 7 files changed, 91 insertions(+), 20 deletions(-)

diff --git a/cores/arduino/HardwareSerial.cpp b/cores/arduino/HardwareSerial.cpp
index 56eb744fa..417e77af1 100644
--- a/cores/arduino/HardwareSerial.cpp
+++ b/cores/arduino/HardwareSerial.cpp
@@ -114,6 +114,14 @@ void HardwareSerial::_tx_udr_empty_irq(void)
   }
 }
 
+void HardwareSerial::_tx_complete_irq(void)
+{
+  // user send function was attached -> call it
+  if (_isrTx) {
+    _isrTx();
+  }
+}
+
 // Public Methods //////////////////////////////////////////////////////////////
 
 void HardwareSerial::begin(unsigned long baud, byte config)
@@ -160,6 +168,7 @@ void HardwareSerial::end()
   cbi(*_ucsrb, TXEN0);
   cbi(*_ucsrb, RXCIE0);
   cbi(*_ucsrb, UDRIE0);
+  cbi(*_ucsrb, TXCIE0);
   
   // clear any received data
   _rx_buffer_head = _rx_buffer_tail;
@@ -280,11 +289,29 @@ size_t HardwareSerial::write(uint8_t c)
   return 1;
 }
 
-void HardwareSerial::attachInterrupt( isr_t fn )
+void HardwareSerial::attachInterrupt_Receive( isrRx_t fn )
+{
+  uint8_t oldSREG = SREG;
+  cli();
+  _isrRx = fn;
+  SREG = oldSREG;
+}
+
+void HardwareSerial::attachInterrupt_Send( isrTx_t fn )
+{
+  uint8_t oldSREG = SREG;
+  cli();
+  _isrTx = fn;
+  sbi(*_ucsrb, TXCIE0);
+  SREG = oldSREG;
+}
+
+void HardwareSerial::detachInterrupt_Send()
 {
   uint8_t oldSREG = SREG;
   cli();
-  _isr = fn;
+  _isrTx = NULL;
+  cbi(*_ucsrb, TXCIE0);
   SREG = oldSREG;
 }
 
diff --git a/cores/arduino/HardwareSerial.h b/cores/arduino/HardwareSerial.h
index f8a3bc65b..1e3de78a7 100644
--- a/cores/arduino/HardwareSerial.h
+++ b/cores/arduino/HardwareSerial.h
@@ -139,12 +139,17 @@ class HardwareSerial : public Stream
     // Interrupt handlers - Not intended to be called externally
     inline void _rx_complete_irq(void);
     void _tx_udr_empty_irq(void);
-
-    typedef void (* isr_t)( uint8_t d, uint8_t s );
-    void attachInterrupt( isr_t fn );
-    void detachInterrupt() { attachInterrupt( (isr_t) NULL ); };
+    void _tx_complete_irq(void);
+
+    typedef void (* isrRx_t)( uint8_t d, uint8_t s );
+    void attachInterrupt_Receive( isrRx_t fn );
+    void detachInterrupt_Receive() { attachInterrupt_Receive( (isrRx_t) NULL ); };
+    typedef void (* isrTx_t)( void );
+    void attachInterrupt_Send( isrTx_t fn );
+    void detachInterrupt_Send( void );
   private:
-    isr_t  _isr;
+    isrRx_t  _isrRx;
+    isrTx_t  _isrTx;
 
     HardwareSerial( const HardwareSerial & );
     HardwareSerial & operator =( const HardwareSerial &);
diff --git a/cores/arduino/HardwareSerial0.cpp b/cores/arduino/HardwareSerial0.cpp
index ece78a636..9f507b6c2 100644
--- a/cores/arduino/HardwareSerial0.cpp
+++ b/cores/arduino/HardwareSerial0.cpp
@@ -20,8 +20,7 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
-  Modified 2 November 2015 by SlashDev
-  Modified 7 November 2019 by Georg Icking-Konert
+  Modified 17 November 2019 by Georg Icking-Konert
 */
 
 #include "Arduino.h"
@@ -66,6 +65,19 @@ ISR(USART_UDRE_vect)
   Serial._tx_udr_empty_irq();
 }
 
+#if defined(UART0_TX_vect)
+ISR(UART0_TX_vect)
+#elif defined(USART0_TX_vect)
+ISR(USART0_TX_vect)
+#elif defined(USART_TX_vect)
+ISR(USART_TX_vect)
+#else
+  #error "Don't know what the Transmission Complete vector is called for Serial"
+#endif
+{
+  Serial._tx_complete_irq();
+}
+
 #if defined(UBRRH) && defined(UBRRL)
   HardwareSerial Serial(&UBRRH, &UBRRL, &UCSRA, &UCSRB, &UCSRC, &UDR);
 #else
diff --git a/cores/arduino/HardwareSerial1.cpp b/cores/arduino/HardwareSerial1.cpp
index c436e1690..800191700 100644
--- a/cores/arduino/HardwareSerial1.cpp
+++ b/cores/arduino/HardwareSerial1.cpp
@@ -20,8 +20,7 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
-  Modified 2 November 2015 by SlashDev
-  Modified 7 November 2019 by Georg Icking-Konert
+  Modified 17 November 2019 by Georg Icking-Konert
 */
 
 #include "Arduino.h"
@@ -60,6 +59,17 @@ ISR(USART1_UDRE_vect)
   Serial1._tx_udr_empty_irq();
 }
 
+#if defined(UART1_TX_vect)
+ISR(UART1_TX_vect)
+#elif defined(USART1_TX_vect)
+ISR(USART1_TX_vect)
+#else
+  #error "Don't know what the Transmission Complete vector is called for Serial1"
+#endif
+{
+  Serial1._tx_complete_irq();
+}
+
 HardwareSerial Serial1(&UBRR1H, &UBRR1L, &UCSR1A, &UCSR1B, &UCSR1C, &UDR1);
 
 // Function that can be weakly referenced by serialEventRun to prevent
diff --git a/cores/arduino/HardwareSerial2.cpp b/cores/arduino/HardwareSerial2.cpp
index 5558b17d1..c87607a47 100644
--- a/cores/arduino/HardwareSerial2.cpp
+++ b/cores/arduino/HardwareSerial2.cpp
@@ -20,8 +20,7 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
-  Modified 2 November 2015 by SlashDev
-  Modified 7 November 2019 by Georg Icking-Konert
+  Modified 17 November 2019 by Georg Icking-Konert
 */
 
 #include "Arduino.h"
@@ -38,6 +37,9 @@
 
 #if defined(HAVE_HWSERIAL2)
 
+// xxx
+extern int count;
+
 ISR(USART2_RX_vect)
 {
   Serial2._rx_complete_irq();
@@ -45,9 +47,20 @@ ISR(USART2_RX_vect)
 
 ISR(USART2_UDRE_vect)
 {
+  // xxx
+  Serial.println(++count);
+  digitalWrite(LED_BUILTIN, HIGH);
+  delayMicroseconds(50);
+  digitalWrite(LED_BUILTIN, LOW);
+
   Serial2._tx_udr_empty_irq();
 }
 
+ISR(USART2_TX_vect)
+{
+  Serial2._tx_complete_irq();
+}
+
 HardwareSerial Serial2(&UBRR2H, &UBRR2L, &UCSR2A, &UCSR2B, &UCSR2C, &UDR2);
 
 // Function that can be weakly referenced by serialEventRun to prevent
diff --git a/cores/arduino/HardwareSerial3.cpp b/cores/arduino/HardwareSerial3.cpp
index f6ba55460..aaac520a5 100644
--- a/cores/arduino/HardwareSerial3.cpp
+++ b/cores/arduino/HardwareSerial3.cpp
@@ -20,8 +20,7 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
-  Modified 2 November 2015 by SlashDev
-  Modified 7 November 2019 by Georg Icking-Konert
+  Modified 17 November 2019 by Georg Icking-Konert
 */
 
 #include "Arduino.h"
@@ -48,6 +47,11 @@ ISR(USART3_UDRE_vect)
   Serial3._tx_udr_empty_irq();
 }
 
+ISR(USART3_TX_vect)
+{
+  Serial3._tx_complete_irq();
+}
+
 HardwareSerial Serial3(&UBRR3H, &UBRR3L, &UCSR3A, &UCSR3B, &UCSR3C, &UDR3);
 
 // Function that can be weakly referenced by serialEventRun to prevent
diff --git a/cores/arduino/HardwareSerial_private.h b/cores/arduino/HardwareSerial_private.h
index 72a9063b3..ac61bed20 100644
--- a/cores/arduino/HardwareSerial_private.h
+++ b/cores/arduino/HardwareSerial_private.h
@@ -20,7 +20,7 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 2 November 2015 by SlashDev
-  Modified 7 November 2019 by Georg Icking-Konert
+  Modified 17 November 2019 by Georg Icking-Konert
 */
 
 #include "wiring_private.h"
@@ -95,7 +95,7 @@ HardwareSerial::HardwareSerial(
     _udr(udr),
     _rx_buffer_head(0), _rx_buffer_tail(0),
     _tx_buffer_head(0), _tx_buffer_tail(0),
-    _isr(0)
+    _isrRx(0), _isrTx(0)
 {
 }
 
@@ -103,11 +103,11 @@ HardwareSerial::HardwareSerial(
 
 void HardwareSerial::_rx_complete_irq(void)
 {
-  // user function was attached -> call it with data and status byte 
-  if (_isr) {
+  // user receive function was attached -> call it with data and status byte 
+  if (_isrRx) {
     unsigned char status = *_ucsra;
     unsigned char data = *_udr;
-    _isr( data, status );
+    _isrRx( data, status );
   }
 
   // default: save data in ring buffer

From f7f584b1ba5078517e391fad8a3da1c627ad6960 Mon Sep 17 00:00:00 2001
From: Georg Icking-Konert <icking@onlinehome.de>
Date: Mon, 18 Nov 2019 18:26:43 +0100
Subject: [PATCH 4/8] add Serial.attachInterrupt_Send()

---
 cores/arduino/HardwareSerial.cpp  | 1 +
 cores/arduino/HardwareSerial2.cpp | 9 ---------
 2 files changed, 1 insertion(+), 9 deletions(-)

diff --git a/cores/arduino/HardwareSerial.cpp b/cores/arduino/HardwareSerial.cpp
index 417e77af1..ffabbb735 100644
--- a/cores/arduino/HardwareSerial.cpp
+++ b/cores/arduino/HardwareSerial.cpp
@@ -120,6 +120,7 @@ void HardwareSerial::_tx_complete_irq(void)
   if (_isrTx) {
     _isrTx();
   }
+
 }
 
 // Public Methods //////////////////////////////////////////////////////////////
diff --git a/cores/arduino/HardwareSerial2.cpp b/cores/arduino/HardwareSerial2.cpp
index c87607a47..1a3b7d754 100644
--- a/cores/arduino/HardwareSerial2.cpp
+++ b/cores/arduino/HardwareSerial2.cpp
@@ -37,9 +37,6 @@
 
 #if defined(HAVE_HWSERIAL2)
 
-// xxx
-extern int count;
-
 ISR(USART2_RX_vect)
 {
   Serial2._rx_complete_irq();
@@ -47,12 +44,6 @@ ISR(USART2_RX_vect)
 
 ISR(USART2_UDRE_vect)
 {
-  // xxx
-  Serial.println(++count);
-  digitalWrite(LED_BUILTIN, HIGH);
-  delayMicroseconds(50);
-  digitalWrite(LED_BUILTIN, LOW);
-
   Serial2._tx_udr_empty_irq();
 }
 

From 307a108582edf6786a0e8d8c7fa4c6d4f78143e4 Mon Sep 17 00:00:00 2001
From: Georg Icking-Konert <icking@onlinehome.de>
Date: Sat, 23 Nov 2019 09:11:38 +0100
Subject: [PATCH 5/8] optimized runtime for TXC custom function

optimized runtime for TXC custom function
---
 cores/arduino/HardwareSerial.cpp       | 32 +++++++++++---------------
 cores/arduino/HardwareSerial.h         | 14 +++++++----
 cores/arduino/HardwareSerial_private.h | 11 ++++++++-
 3 files changed, 32 insertions(+), 25 deletions(-)

diff --git a/cores/arduino/HardwareSerial.cpp b/cores/arduino/HardwareSerial.cpp
index ffabbb735..74ee0040a 100644
--- a/cores/arduino/HardwareSerial.cpp
+++ b/cores/arduino/HardwareSerial.cpp
@@ -79,6 +79,9 @@ void serialEventRun(void)
 #endif
 }
 
+// dummy function attached to TxC interrupt. Is faster than if(NULL) check 
+void dummyFct(void) { /* dummy */}
+
 // macro to guard critical sections when needed for large TX buffer sizes
 #if (SERIAL_TX_BUFFER_SIZE>256)
 #define TX_BUFFER_ATOMIC ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
@@ -114,15 +117,6 @@ void HardwareSerial::_tx_udr_empty_irq(void)
   }
 }
 
-void HardwareSerial::_tx_complete_irq(void)
-{
-  // user send function was attached -> call it
-  if (_isrTx) {
-    _isrTx();
-  }
-
-}
-
 // Public Methods //////////////////////////////////////////////////////////////
 
 void HardwareSerial::begin(unsigned long baud, byte config)
@@ -158,6 +152,7 @@ void HardwareSerial::begin(unsigned long baud, byte config)
   sbi(*_ucsrb, TXEN0);
   sbi(*_ucsrb, RXCIE0);
   cbi(*_ucsrb, UDRIE0);
+  //cbi(*_ucsrb, TXCIE0);
 }
 
 void HardwareSerial::end()
@@ -300,20 +295,19 @@ void HardwareSerial::attachInterrupt_Receive( isrRx_t fn )
 
 void HardwareSerial::attachInterrupt_Send( isrTx_t fn )
 {
-  uint8_t oldSREG = SREG;
-  cli();
-  _isrTx = fn;
-  sbi(*_ucsrb, TXCIE0);
-  SREG = oldSREG;
+  ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
+    _isrTx = fn;
+    sbi(*_ucsra, TXC0);      // clear TXC status
+    sbi(*_ucsrb, TXCIE0);    // activate TXC interrupt
+  }
 }
 
 void HardwareSerial::detachInterrupt_Send()
 {
-  uint8_t oldSREG = SREG;
-  cli();
-  _isrTx = NULL;
-  cbi(*_ucsrb, TXCIE0);
-  SREG = oldSREG;
+  ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
+    _isrTx = NULL;
+    cbi(*_ucsrb, TXCIE0);    // deactivate TXC interrupt
+  }
 }
 
 #endif // whole file
diff --git a/cores/arduino/HardwareSerial.h b/cores/arduino/HardwareSerial.h
index 1e3de78a7..a9354877b 100644
--- a/cores/arduino/HardwareSerial.h
+++ b/cores/arduino/HardwareSerial.h
@@ -114,6 +114,12 @@ class HardwareSerial : public Stream
     // instruction.
     unsigned char _rx_buffer[SERIAL_RX_BUFFER_SIZE];
     unsigned char _tx_buffer[SERIAL_TX_BUFFER_SIZE];
+    
+    // custom handlers for RX and TXC interrupts 
+    typedef void (* isrRx_t)( uint8_t d, uint8_t s );
+    typedef void (* isrTx_t)( void );
+    isrRx_t  _isrRx;
+    isrTx_t  _isrTx;
 
   public:
     inline HardwareSerial(
@@ -139,17 +145,15 @@ class HardwareSerial : public Stream
     // Interrupt handlers - Not intended to be called externally
     inline void _rx_complete_irq(void);
     void _tx_udr_empty_irq(void);
-    void _tx_complete_irq(void);
+    inline void _tx_complete_irq(void);
 
-    typedef void (* isrRx_t)( uint8_t d, uint8_t s );
+    // attach custom handlers for RX and TXC interrupts 
     void attachInterrupt_Receive( isrRx_t fn );
     void detachInterrupt_Receive() { attachInterrupt_Receive( (isrRx_t) NULL ); };
-    typedef void (* isrTx_t)( void );
     void attachInterrupt_Send( isrTx_t fn );
     void detachInterrupt_Send( void );
+
   private:
-    isrRx_t  _isrRx;
-    isrTx_t  _isrTx;
 
     HardwareSerial( const HardwareSerial & );
     HardwareSerial & operator =( const HardwareSerial &);
diff --git a/cores/arduino/HardwareSerial_private.h b/cores/arduino/HardwareSerial_private.h
index ac61bed20..575d519f4 100644
--- a/cores/arduino/HardwareSerial_private.h
+++ b/cores/arduino/HardwareSerial_private.h
@@ -84,6 +84,9 @@
 #error "Not all bit positions for UART3 are the same as for UART0"
 #endif
 
+// dummy custom function attached and TXC interrupt. Is faster than if(NULL) check 
+void dummyFct(void);
+
 // Constructors ////////////////////////////////////////////////////////////////
 
 HardwareSerial::HardwareSerial(
@@ -95,7 +98,7 @@ HardwareSerial::HardwareSerial(
     _udr(udr),
     _rx_buffer_head(0), _rx_buffer_tail(0),
     _tx_buffer_head(0), _tx_buffer_tail(0),
-    _isrRx(0), _isrTx(0)
+    _isrRx(dummyFct), _isrTx(dummyFct)
 {
 }
 
@@ -134,4 +137,10 @@ void HardwareSerial::_rx_complete_irq(void)
   }
 }
 
+void HardwareSerial::_tx_complete_irq(void)
+{
+  // user send function was attached -> call it
+  _isrTx();
+}
+
 #endif // whole file

From cbcc356652ec3c5be1ae07df87311fafee1ecd67 Mon Sep 17 00:00:00 2001
From: Georg Icking-Konert <icking@onlinehome.de>
Date: Sat, 23 Nov 2019 13:57:38 +0100
Subject: [PATCH 6/8] minor cosmetics

minor cosmetics
---
 cores/arduino/HardwareSerial.cpp       | 10 +++++-----
 cores/arduino/HardwareSerial.h         |  5 ++++-
 cores/arduino/HardwareSerial_private.h |  5 +----
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/cores/arduino/HardwareSerial.cpp b/cores/arduino/HardwareSerial.cpp
index 74ee0040a..fc3716bc4 100644
--- a/cores/arduino/HardwareSerial.cpp
+++ b/cores/arduino/HardwareSerial.cpp
@@ -79,9 +79,6 @@ void serialEventRun(void)
 #endif
 }
 
-// dummy function attached to TxC interrupt. Is faster than if(NULL) check 
-void dummyFct(void) { /* dummy */}
-
 // macro to guard critical sections when needed for large TX buffer sizes
 #if (SERIAL_TX_BUFFER_SIZE>256)
 #define TX_BUFFER_ATOMIC ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
@@ -89,6 +86,9 @@ void dummyFct(void) { /* dummy */}
 #define TX_BUFFER_ATOMIC
 #endif
 
+// dummy custom function for TxC interrupt. Is faster than check if(fct==NULL) 
+void dummyTxFct(void) { /* dummy */}
+
 // Actual interrupt handlers //////////////////////////////////////////////////////////////
 
 void HardwareSerial::_tx_udr_empty_irq(void)
@@ -296,7 +296,7 @@ void HardwareSerial::attachInterrupt_Receive( isrRx_t fn )
 void HardwareSerial::attachInterrupt_Send( isrTx_t fn )
 {
   ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
-    _isrTx = fn;
+    _isrTx = fn;             // set custom function
     sbi(*_ucsra, TXC0);      // clear TXC status
     sbi(*_ucsrb, TXCIE0);    // activate TXC interrupt
   }
@@ -305,7 +305,7 @@ void HardwareSerial::attachInterrupt_Send( isrTx_t fn )
 void HardwareSerial::detachInterrupt_Send()
 {
   ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
-    _isrTx = NULL;
+    _isrTx = dummyTxFct;     // restore dummy function
     cbi(*_ucsrb, TXCIE0);    // deactivate TXC interrupt
   }
 }
diff --git a/cores/arduino/HardwareSerial.h b/cores/arduino/HardwareSerial.h
index a9354877b..b39590496 100644
--- a/cores/arduino/HardwareSerial.h
+++ b/cores/arduino/HardwareSerial.h
@@ -92,6 +92,9 @@ typedef uint8_t rx_buffer_index_t;
 #define SERIAL_7O2 0x3C
 #define SERIAL_8O2 0x3E
 
+// dummy custom function for TxC interrupt. Is faster than check if(fct==NULL) 
+void dummyTxFct(void);
+
 class HardwareSerial : public Stream
 {
   protected:
@@ -149,7 +152,7 @@ class HardwareSerial : public Stream
 
     // attach custom handlers for RX and TXC interrupts 
     void attachInterrupt_Receive( isrRx_t fn );
-    void detachInterrupt_Receive() { attachInterrupt_Receive( (isrRx_t) NULL ); };
+    void detachInterrupt_Receive( void ) { attachInterrupt_Receive( (isrRx_t) NULL ); };
     void attachInterrupt_Send( isrTx_t fn );
     void detachInterrupt_Send( void );
 
diff --git a/cores/arduino/HardwareSerial_private.h b/cores/arduino/HardwareSerial_private.h
index 575d519f4..5446ab619 100644
--- a/cores/arduino/HardwareSerial_private.h
+++ b/cores/arduino/HardwareSerial_private.h
@@ -84,9 +84,6 @@
 #error "Not all bit positions for UART3 are the same as for UART0"
 #endif
 
-// dummy custom function attached and TXC interrupt. Is faster than if(NULL) check 
-void dummyFct(void);
-
 // Constructors ////////////////////////////////////////////////////////////////
 
 HardwareSerial::HardwareSerial(
@@ -98,7 +95,7 @@ HardwareSerial::HardwareSerial(
     _udr(udr),
     _rx_buffer_head(0), _rx_buffer_tail(0),
     _tx_buffer_head(0), _tx_buffer_tail(0),
-    _isrRx(dummyFct), _isrTx(dummyFct)
+    _isrRx(NULL), _isrTx(dummyTxFct)
 {
 }
 

From b4f39848dd457d7e5342295fcbd98d6153ee297e Mon Sep 17 00:00:00 2001
From: Georg Icking-Konert <icking@onlinehome.de>
Date: Sat, 23 Nov 2019 14:14:39 +0100
Subject: [PATCH 7/8] updated modification date

- updated modification date to sync with SAM core
- no functional change
---
 cores/arduino/HardwareSerial.cpp       | 2 +-
 cores/arduino/HardwareSerial.h         | 2 +-
 cores/arduino/HardwareSerial0.cpp      | 2 +-
 cores/arduino/HardwareSerial1.cpp      | 2 +-
 cores/arduino/HardwareSerial2.cpp      | 2 +-
 cores/arduino/HardwareSerial3.cpp      | 2 +-
 cores/arduino/HardwareSerial_private.h | 2 +-
 7 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/cores/arduino/HardwareSerial.cpp b/cores/arduino/HardwareSerial.cpp
index fc3716bc4..39984fc36 100644
--- a/cores/arduino/HardwareSerial.cpp
+++ b/cores/arduino/HardwareSerial.cpp
@@ -21,7 +21,7 @@
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
   Modified 2 November 2015 by SlashDev
-  Modified 7 November 2019 by Georg Icking-Konert
+  Modified 23 November 2019 by Georg Icking-Konert
 */
 
 #include <stdlib.h>
diff --git a/cores/arduino/HardwareSerial.h b/cores/arduino/HardwareSerial.h
index b39590496..b7368ccc5 100644
--- a/cores/arduino/HardwareSerial.h
+++ b/cores/arduino/HardwareSerial.h
@@ -20,7 +20,7 @@
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
   Modified 2 November 2015 by SlashDev
-  Modified 7 November 2019 by Georg Icking-Konert
+  Modified 23 November 2019 by Georg Icking-Konert
 */
 
 #ifndef HardwareSerial_h
diff --git a/cores/arduino/HardwareSerial0.cpp b/cores/arduino/HardwareSerial0.cpp
index 9f507b6c2..33810d21d 100644
--- a/cores/arduino/HardwareSerial0.cpp
+++ b/cores/arduino/HardwareSerial0.cpp
@@ -20,7 +20,7 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
-  Modified 17 November 2019 by Georg Icking-Konert
+  Modified 23 November 2019 by Georg Icking-Konert
 */
 
 #include "Arduino.h"
diff --git a/cores/arduino/HardwareSerial1.cpp b/cores/arduino/HardwareSerial1.cpp
index 800191700..2dbad872d 100644
--- a/cores/arduino/HardwareSerial1.cpp
+++ b/cores/arduino/HardwareSerial1.cpp
@@ -20,7 +20,7 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
-  Modified 17 November 2019 by Georg Icking-Konert
+  Modified 23 November 2019 by Georg Icking-Konert
 */
 
 #include "Arduino.h"
diff --git a/cores/arduino/HardwareSerial2.cpp b/cores/arduino/HardwareSerial2.cpp
index 1a3b7d754..a06569a37 100644
--- a/cores/arduino/HardwareSerial2.cpp
+++ b/cores/arduino/HardwareSerial2.cpp
@@ -20,7 +20,7 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
-  Modified 17 November 2019 by Georg Icking-Konert
+  Modified 23 November 2019 by Georg Icking-Konert
 */
 
 #include "Arduino.h"
diff --git a/cores/arduino/HardwareSerial3.cpp b/cores/arduino/HardwareSerial3.cpp
index aaac520a5..b010858ba 100644
--- a/cores/arduino/HardwareSerial3.cpp
+++ b/cores/arduino/HardwareSerial3.cpp
@@ -20,7 +20,7 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
-  Modified 17 November 2019 by Georg Icking-Konert
+  Modified 23 November 2019 by Georg Icking-Konert
 */
 
 #include "Arduino.h"
diff --git a/cores/arduino/HardwareSerial_private.h b/cores/arduino/HardwareSerial_private.h
index 5446ab619..ee1dd611d 100644
--- a/cores/arduino/HardwareSerial_private.h
+++ b/cores/arduino/HardwareSerial_private.h
@@ -20,7 +20,7 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 2 November 2015 by SlashDev
-  Modified 17 November 2019 by Georg Icking-Konert
+  Modified 23 November 2019 by Georg Icking-Konert
 */
 
 #include "wiring_private.h"

From eb648c1efd108f01c189193d33700a9259626fa3 Mon Sep 17 00:00:00 2001
From: Georg Icking-Konert <icking@onlinehome.de>
Date: Fri, 24 Dec 2021 09:28:45 +0100
Subject: [PATCH 8/8] added optional argument pointer

added optional argument pointer, see https://github.com/arduino/ArduinoCore-sam/pull/95#issuecomment-999825944
---
 cores/arduino/HardwareSerial.cpp       | 3 ++-
 cores/arduino/HardwareSerial.h         | 5 +++--
 cores/arduino/HardwareSerial_private.h | 6 +++---
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/cores/arduino/HardwareSerial.cpp b/cores/arduino/HardwareSerial.cpp
index 39984fc36..e8eae9524 100644
--- a/cores/arduino/HardwareSerial.cpp
+++ b/cores/arduino/HardwareSerial.cpp
@@ -285,11 +285,12 @@ size_t HardwareSerial::write(uint8_t c)
   return 1;
 }
 
-void HardwareSerial::attachInterrupt_Receive( isrRx_t fn )
+void HardwareSerial::attachInterrupt_Receive( isrRx_t fn, void* args )
 {
   uint8_t oldSREG = SREG;
   cli();
   _isrRx = fn;
+  _rxArg = args;
   SREG = oldSREG;
 }
 
diff --git a/cores/arduino/HardwareSerial.h b/cores/arduino/HardwareSerial.h
index b7368ccc5..14c29c2ce 100644
--- a/cores/arduino/HardwareSerial.h
+++ b/cores/arduino/HardwareSerial.h
@@ -119,10 +119,11 @@ class HardwareSerial : public Stream
     unsigned char _tx_buffer[SERIAL_TX_BUFFER_SIZE];
     
     // custom handlers for RX and TXC interrupts 
-    typedef void (* isrRx_t)( uint8_t d, uint8_t s );
+    typedef void (* isrRx_t)( uint8_t data, uint8_t status, void* args );
     typedef void (* isrTx_t)( void );
     isrRx_t  _isrRx;
     isrTx_t  _isrTx;
+    void*    _rxArg;
 
   public:
     inline HardwareSerial(
@@ -151,7 +152,7 @@ class HardwareSerial : public Stream
     inline void _tx_complete_irq(void);
 
     // attach custom handlers for RX and TXC interrupts 
-    void attachInterrupt_Receive( isrRx_t fn );
+    void attachInterrupt_Receive( isrRx_t fn, void *args = NULL );
     void detachInterrupt_Receive( void ) { attachInterrupt_Receive( (isrRx_t) NULL ); };
     void attachInterrupt_Send( isrTx_t fn );
     void detachInterrupt_Send( void );
diff --git a/cores/arduino/HardwareSerial_private.h b/cores/arduino/HardwareSerial_private.h
index ee1dd611d..652622508 100644
--- a/cores/arduino/HardwareSerial_private.h
+++ b/cores/arduino/HardwareSerial_private.h
@@ -95,7 +95,7 @@ HardwareSerial::HardwareSerial(
     _udr(udr),
     _rx_buffer_head(0), _rx_buffer_tail(0),
     _tx_buffer_head(0), _tx_buffer_tail(0),
-    _isrRx(NULL), _isrTx(dummyTxFct)
+    _isrRx(NULL), _isrTx(dummyTxFct), _rxArg(NULL)
 {
 }
 
@@ -103,11 +103,11 @@ HardwareSerial::HardwareSerial(
 
 void HardwareSerial::_rx_complete_irq(void)
 {
-  // user receive function was attached -> call it with data and status byte 
+  // user receive function was attached -> call it with data, status byte and optional argument pointer 
   if (_isrRx) {
     unsigned char status = *_ucsra;
     unsigned char data = *_udr;
-    _isrRx( data, status );
+    _isrRx( data, status, _rxArg );
   }
 
   // default: save data in ring buffer