Refactor serial class with templates (#20783)

Marlin/src/HAL/AVR/HAL.cpp

 #include "../../inc/MarlinConfig.h"
 #include "HAL.h"
 
+#ifdef USBCON
+  DefaultSerial MSerial(false, Serial);
+  #ifdef BLUETOOTH
+    BTSerial btSerial(false, bluetoothSerial);
+  #endif
+#endif
+
 // ------------------------
 // Public Variables
 // ------------------------

Marlin/src/HAL/AVR/HAL.h

 
 // Serial ports
 #ifdef USBCON
-  #define MYSERIAL0 TERN(BLUETOOTH, bluetoothSerial, Serial)
+  #include "../../core/serial_hook.h" 
+  typedef ForwardSerial0Type< decltype(Serial) > DefaultSerial;
+  extern DefaultSerial MSerial;
+  #ifdef BLUETOOTH
+    typedef ForwardSerial0Type< decltype(bluetoothSerial) > BTSerial;
+    extern BTSerial btSerial;
+  #endif
+  
+  #define MYSERIAL0 TERN(BLUETOOTH, btSerial, MSerial)
 #else
   #if !WITHIN(SERIAL_PORT, -1, 3)
     #error "SERIAL_PORT must be from -1 to 3. Please update your configuration."

Marlin/src/HAL/AVR/MarlinSerial.cpp

 }
 
 template<typename Cfg>
-void MarlinSerial<Cfg>::write(const uint8_t c) {
+size_t MarlinSerial<Cfg>::write(const uint8_t c) {
   if (Cfg::TX_SIZE == 0) {
 
     _written = true;
       // location". This makes sure flush() won't return until the bytes
       // actually got written
       B_TXC = 1;
-      return;
+      return 1;
     }
 
     const uint8_t i = (tx_buffer.head + 1) & (Cfg::TX_SIZE - 1);
     // Enable TX ISR - Non atomic, but it will eventually enable TX ISR
     B_UDRIE = 1;
   }
+  return 1;
 }
 
 template<typename Cfg>
   }
 }
 
-/**
- * Imports from print.h
- */
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::print(char c, int base) {
-  print((long)c, base);
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::print(unsigned char b, int base) {
-  print((unsigned long)b, base);
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::print(int n, int base) {
-  print((long)n, base);
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::print(unsigned int n, int base) {
-  print((unsigned long)n, base);
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::print(long n, int base) {
-  if (base == 0) write(n);
-  else if (base == 10) {
-    if (n < 0) { print('-'); n = -n; }
-    printNumber(n, 10);
-  }
-  else
-    printNumber(n, base);
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::print(unsigned long n, int base) {
-  if (base == 0) write(n);
-  else printNumber(n, base);
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::print(double n, int digits) {
-  printFloat(n, digits);
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println() {
-  print('\r');
-  print('\n');
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(const String& s) {
-  print(s);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(const char c[]) {
-  print(c);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(char c, int base) {
-  print(c, base);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(unsigned char b, int base) {
-  print(b, base);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(int n, int base) {
-  print(n, base);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(unsigned int n, int base) {
-  print(n, base);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(long n, int base) {
-  print(n, base);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(unsigned long n, int base) {
-  print(n, base);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(double n, int digits) {
-  print(n, digits);
-  println();
-}
-
-// Private Methods
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::printNumber(unsigned long n, uint8_t base) {
-  if (n) {
-    unsigned char buf[8 * sizeof(long)]; // Enough space for base 2
-    int8_t i = 0;
-    while (n) {
-      buf[i++] = n % base;
-      n /= base;
-    }
-    while (i--)
-      print((char)(buf[i] + (buf[i] < 10 ? '0' : 'A' - 10)));
-  }
-  else
-    print('0');
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::printFloat(double number, uint8_t digits) {
-  // Handle negative numbers
-  if (number < 0.0) {
-    print('-');
-    number = -number;
-  }
-
-  // Round correctly so that print(1.999, 2) prints as "2.00"
-  double rounding = 0.5;
-  LOOP_L_N(i, digits) rounding *= 0.1;
-  number += rounding;
-
-  // Extract the integer part of the number and print it
-  unsigned long int_part = (unsigned long)number;
-  double remainder = number - (double)int_part;
-  print(int_part);
-
-  // Print the decimal point, but only if there are digits beyond
-  if (digits) {
-    print('.');
-    // Extract digits from the remainder one at a time
-    while (digits--) {
-      remainder *= 10.0;
-      int toPrint = int(remainder);
-      print(toPrint);
-      remainder -= toPrint;
-    }
-  }
-}
-
 // Hookup ISR handlers
 ISR(SERIAL_REGNAME(USART, SERIAL_PORT, _RX_vect)) {
   MarlinSerial<MarlinSerialCfg<SERIAL_PORT>>::store_rxd_char();
   MarlinSerial<MarlinSerialCfg<SERIAL_PORT>>::_tx_udr_empty_irq();
 }
 
-// Preinstantiate
-template class MarlinSerial<MarlinSerialCfg<SERIAL_PORT>>;
-
-// Instantiate
-MarlinSerial<MarlinSerialCfg<SERIAL_PORT>> customizedSerial1;
+// Because of the template definition above, it's required to instantiate the template to have all method generated
+template class MarlinSerial< MarlinSerialCfg<SERIAL_PORT> >;
+MSerialT customizedSerial1(MSerialT::HasEmergencyParser);
 
 #ifdef SERIAL_PORT_2
 
     MarlinSerial<MarlinSerialCfg<SERIAL_PORT_2>>::_tx_udr_empty_irq();
   }
 
-  // Preinstantiate
-  template class MarlinSerial<MarlinSerialCfg<SERIAL_PORT_2>>;
-
-  // Instantiate
-  MarlinSerial<MarlinSerialCfg<SERIAL_PORT_2>> customizedSerial2;
-
+  template class MarlinSerial< MarlinSerialCfg<SERIAL_PORT_2> >;
+  MSerialT2 customizedSerial2(MSerialT2::HasEmergencyParser);
 #endif
 
 #ifdef MMU2_SERIAL_PORT
     MarlinSerial<MMU2SerialCfg<MMU2_SERIAL_PORT>>::_tx_udr_empty_irq();
   }
 
-  // Preinstantiate
-  template class MarlinSerial<MMU2SerialCfg<MMU2_SERIAL_PORT>>;
-
-  // Instantiate
-  MarlinSerial<MMU2SerialCfg<MMU2_SERIAL_PORT>> mmuSerial;
-
+  template class MarlinSerial< MarlinSerialCfg<MMU2_SERIAL_PORT> >;
+  MSerialT3 mmuSerial(MSerialT3::HasEmergencyParser);
 #endif
 
 #ifdef LCD_SERIAL_PORT
     MarlinSerial<LCDSerialCfg<LCD_SERIAL_PORT>>::_tx_udr_empty_irq();
   }
 
-  // Preinstantiate
-  template class MarlinSerial<LCDSerialCfg<LCD_SERIAL_PORT>>;
-
-  // Instantiate
-  MarlinSerial<LCDSerialCfg<LCD_SERIAL_PORT>> lcdSerial;
-
+  template class MarlinSerial< LCDSerialCfg<LCD_SERIAL_PORT> >;
+  MSerialT4 lcdSerial(MSerialT4::HasEmergencyParser);
+ 
   #if HAS_DGUS_LCD
     template<typename Cfg>
     typename MarlinSerial<Cfg>::ring_buffer_pos_t MarlinSerial<Cfg>::get_tx_buffer_free() {
 
 // For AT90USB targets use the UART for BT interfacing
 #if defined(USBCON) && ENABLED(BLUETOOTH)
-  HardwareSerial bluetoothSerial;
+  MSerialT5 bluetoothSerial(false);
 #endif
 
 #endif // __AVR__

Marlin/src/HAL/AVR/MarlinSerial.h

 #include <WString.h>
 
 #include "../../inc/MarlinConfigPre.h"
+#include "../../core/serial_hook.h"
 
 #ifndef SERIAL_PORT
   #define SERIAL_PORT 0
     UART_DECL(3);
   #endif
 
-  #define DEC 10
-  #define HEX 16
-  #define OCT 8
-  #define BIN 2
   #define BYTE 0
 
   // Templated type selector
     static FORCE_INLINE void atomic_set_rx_tail(ring_buffer_pos_t value);
     static FORCE_INLINE ring_buffer_pos_t atomic_read_rx_tail();
 
-    public:
-
+  public:
     FORCE_INLINE static void store_rxd_char();
     FORCE_INLINE static void _tx_udr_empty_irq();
 
-    public:
-      MarlinSerial() {};
-      static void begin(const long);
-      static void end();
-      static int peek();
-      static int read();
-      static void flush();
-      static ring_buffer_pos_t available();
-      static void write(const uint8_t c);
-      static void flushTX();
-      #if HAS_DGUS_LCD
-        static ring_buffer_pos_t get_tx_buffer_free();
-      #endif
-
-      static inline bool emergency_parser_enabled() { return Cfg::EMERGENCYPARSER; }
-
-      FORCE_INLINE static uint8_t dropped() { return Cfg::DROPPED_RX ? rx_dropped_bytes : 0; }
-      FORCE_INLINE static uint8_t buffer_overruns() { return Cfg::RX_OVERRUNS ? rx_buffer_overruns : 0; }
-      FORCE_INLINE static uint8_t framing_errors() { return Cfg::RX_FRAMING_ERRORS ? rx_framing_errors : 0; }
-      FORCE_INLINE static ring_buffer_pos_t rxMaxEnqueued() { return Cfg::MAX_RX_QUEUED ? rx_max_enqueued : 0; }
-
-      FORCE_INLINE static void write(const char* str) { while (*str) write(*str++); }
-      FORCE_INLINE static void write(const uint8_t* buffer, size_t size) { while (size--) write(*buffer++); }
-      FORCE_INLINE static void print(const String& s) { for (int i = 0; i < (int)s.length(); i++) write(s[i]); }
-      FORCE_INLINE static void print(const char* str) { write(str); }
-
-      static void print(char, int = BYTE);
-      static void print(unsigned char, int = BYTE);
-      static void print(int, int = DEC);
-      static void print(unsigned int, int = DEC);
-      static void print(long, int = DEC);
-      static void print(unsigned long, int = DEC);
-      static void print(double, int = 2);
-
-      static void println(const String& s);
-      static void println(const char[]);
-      static void println(char, int = BYTE);
-      static void println(unsigned char, int = BYTE);
-      static void println(int, int = DEC);
-      static void println(unsigned int, int = DEC);
-      static void println(long, int = DEC);
-      static void println(unsigned long, int = DEC);
-      static void println(double, int = 2);
-      static void println();
-      operator bool() { return true; }
-
-    private:
-      static void printNumber(unsigned long, const uint8_t);
-      static void printFloat(double, uint8_t);
+  public:
+    static void begin(const long);
+    static void end();
+    static int peek();
+    static int read();
+    static void flush();
+    static ring_buffer_pos_t available();
+    static size_t write(const uint8_t c);
+    static void flushTX();
+    #if HAS_DGUS_LCD
+      static ring_buffer_pos_t get_tx_buffer_free();
+    #endif
+
+    enum { HasEmergencyParser = Cfg::EMERGENCYPARSER };
+    static inline bool emergency_parser_enabled() { return Cfg::EMERGENCYPARSER; }
+
+    FORCE_INLINE static uint8_t dropped() { return Cfg::DROPPED_RX ? rx_dropped_bytes : 0; }
+    FORCE_INLINE static uint8_t buffer_overruns() { return Cfg::RX_OVERRUNS ? rx_buffer_overruns : 0; }
+    FORCE_INLINE static uint8_t framing_errors() { return Cfg::RX_FRAMING_ERRORS ? rx_framing_errors : 0; }
+    FORCE_INLINE static ring_buffer_pos_t rxMaxEnqueued() { return Cfg::MAX_RX_QUEUED ? rx_max_enqueued : 0; }
   };
 
   template <uint8_t serial>
     static constexpr bool RX_FRAMING_ERRORS = ENABLED(SERIAL_STATS_RX_FRAMING_ERRORS);
     static constexpr bool MAX_RX_QUEUED     = ENABLED(SERIAL_STATS_MAX_RX_QUEUED);
   };
-  extern MarlinSerial<MarlinSerialCfg<SERIAL_PORT>> customizedSerial1;
-
-  #ifdef SERIAL_PORT_2
 
-    extern MarlinSerial<MarlinSerialCfg<SERIAL_PORT_2>> customizedSerial2;
+  typedef Serial0Type< MarlinSerial< MarlinSerialCfg<SERIAL_PORT> > > MSerialT; 
+  extern MSerialT customizedSerial1;
 
+  #ifdef SERIAL_PORT_2
+    typedef Serial0Type< MarlinSerial< MarlinSerialCfg<SERIAL_PORT_2> > > MSerialT2; 
+    extern MSerialT2 customizedSerial2;
   #endif
 
 #endif // !USBCON
     static constexpr bool RX_OVERRUNS       = false;
   };
 
-  extern MarlinSerial<MMU2SerialCfg<MMU2_SERIAL_PORT>> mmuSerial;
+  typedef Serial0Type< MarlinSerial< MMU2SerialCfg<MMU2_SERIAL_PORT> > > MSerialT3; 
+  extern MSerial3 mmuSerial;
 #endif
 
 #ifdef LCD_SERIAL_PORT
     #endif
   };
 
-  extern MarlinSerial<LCDSerialCfg<LCD_SERIAL_PORT>> lcdSerial;
 
+  typedef Serial0Type< MarlinSerial< LCDSerialCfg<LCD_SERIAL_PORT> > > MSerialT4; 
+  extern MSerialT4 lcdSerial;
 #endif
 
 // Use the UART for Bluetooth in AT90USB configurations
 #if defined(USBCON) && ENABLED(BLUETOOTH)
-  extern HardwareSerial bluetoothSerial;
+  typedef Serial0Type<HardwareSerial> MSerialT5;
+  extern MSerialT5 bluetoothSerial;
 #endif

Marlin/src/HAL/DUE/HAL.cpp

   return HAL_adc_result;
 }
 
+// Forward the default serial port
+DefaultSerial MSerial(false, Serial);
+
+DefaultSerial1 MSerial1(false, Serial1);
+DefaultSerial2 MSerial2(false, Serial2);
+DefaultSerial3 MSerial3(false, Serial3);
+
 #endif // ARDUINO_ARCH_SAM

Marlin/src/HAL/DUE/HAL.h

 
 #include <stdint.h>
 
-#define _MSERIAL(X) Serial##X
+#include "../../core/serial_hook.h"
+typedef ForwardSerial0Type< decltype(Serial) > DefaultSerial;
+extern DefaultSerial MSerial;
+
+typedef ForwardSerial0Type< decltype(Serial1) > DefaultSerial1;
+typedef ForwardSerial0Type< decltype(Serial2) > DefaultSerial2;
+typedef ForwardSerial0Type< decltype(Serial3) > DefaultSerial3;
+extern DefaultSerial1 MSerial1;
+extern DefaultSerial2 MSerial2;
+extern DefaultSerial3 MSerial3;
+
+#define _MSERIAL(X) MSerial##X
 #define MSERIAL(X) _MSERIAL(X)
-#define Serial0 Serial
+#define MSerial0 MSerial
 
 // Define MYSERIAL0/1 before MarlinSerial includes!
 #if SERIAL_PORT == -1 || ENABLED(EMERGENCY_PARSER)

Marlin/src/HAL/DUE/MarlinSerial.cpp

 }
 
 template<typename Cfg>
-void MarlinSerial<Cfg>::write(const uint8_t c) {
+size_t MarlinSerial<Cfg>::write(const uint8_t c) {
   _written = true;
 
   if (Cfg::TX_SIZE == 0) {
     // XOFF char at the RX isr, but it is properly handled there
     if (!(HWUART->UART_IMR & UART_IMR_TXRDY) && (HWUART->UART_SR & UART_SR_TXRDY)) {
       HWUART->UART_THR = c;
-      return;
+      return 1;
     }
 
     const uint8_t i = (tx_buffer.head + 1) & (Cfg::TX_SIZE - 1);
     // Enable TX isr - Non atomic, but it will eventually enable TX isr
     HWUART->UART_IER = UART_IER_TXRDY;
   }
+  return 1;
 }
 
 template<typename Cfg>
   }
 }
 
-/**
- * Imports from print.h
- */
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::print(char c, int base) {
-  print((long)c, base);
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::print(unsigned char b, int base) {
-  print((unsigned long)b, base);
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::print(int n, int base) {
-  print((long)n, base);
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::print(unsigned int n, int base) {
-  print((unsigned long)n, base);
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::print(long n, int base) {
-  if (base == 0) write(n);
-  else if (base == 10) {
-    if (n < 0) { print('-'); n = -n; }
-    printNumber(n, 10);
-  }
-  else
-    printNumber(n, base);
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::print(unsigned long n, int base) {
-  if (base == 0) write(n);
-  else printNumber(n, base);
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::print(double n, int digits) {
-  printFloat(n, digits);
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println() {
-  print('\r');
-  print('\n');
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(const String& s) {
-  print(s);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(const char c[]) {
-  print(c);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(char c, int base) {
-  print(c, base);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(unsigned char b, int base) {
-  print(b, base);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(int n, int base) {
-  print(n, base);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(unsigned int n, int base) {
-  print(n, base);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(long n, int base) {
-  print(n, base);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(unsigned long n, int base) {
-  print(n, base);
-  println();
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::println(double n, int digits) {
-  print(n, digits);
-  println();
-}
-
-// Private Methods
-template<typename Cfg>
-void MarlinSerial<Cfg>::printNumber(unsigned long n, uint8_t base) {
-  if (n) {
-    unsigned char buf[8 * sizeof(long)]; // Enough space for base 2
-    int8_t i = 0;
-    while (n) {
-      buf[i++] = n % base;
-      n /= base;
-    }
-    while (i--)
-      print((char)(buf[i] + (buf[i] < 10 ? '0' : 'A' - 10)));
-  }
-  else
-    print('0');
-}
-
-template<typename Cfg>
-void MarlinSerial<Cfg>::printFloat(double number, uint8_t digits) {
-  // Handle negative numbers
-  if (number < 0.0) {
-    print('-');
-    number = -number;
-  }
-
-  // Round correctly so that print(1.999, 2) prints as "2.00"
-  double rounding = 0.5;
-  LOOP_L_N(i, digits) rounding *= 0.1;
-  number += rounding;
-
-  // Extract the integer part of the number and print it
-  unsigned long int_part = (unsigned long)number;
-  double remainder = number - (double)int_part;
-  print(int_part);
-
-  // Print the decimal point, but only if there are digits beyond
-  if (digits) {
-    print('.');
-    // Extract digits from the remainder one at a time
-    while (digits--) {
-      remainder *= 10.0;
-      int toPrint = int(remainder);
-      print(toPrint);
-      remainder -= toPrint;
-    }
-  }
-}
 
 // If not using the USB port as serial port
 #if SERIAL_PORT >= 0
-  template class MarlinSerial<MarlinSerialCfg<SERIAL_PORT>>;      // Define
-  MarlinSerial<MarlinSerialCfg<SERIAL_PORT>> customizedSerial1;   // Instantiate
+  template class MarlinSerial< MarlinSerialCfg<SERIAL_PORT> >;
+  MSerialT customizedSerial1(MarlinSerialCfg<SERIAL_PORT>::EMERGENCYPARSER);
 #endif
 
 #if defined(SERIAL_PORT_2) && SERIAL_PORT_2 >= 0
-  template class MarlinSerial<MarlinSerialCfg<SERIAL_PORT_2>>;    // Define
-  MarlinSerial<MarlinSerialCfg<SERIAL_PORT_2>> customizedSerial2; // Instantiate
+  template class MarlinSerial< MarlinSerialCfg<SERIAL_PORT_2> >;
+  MSerialT2 customizedSerial2(MarlinSerialCfg<SERIAL_PORT_2>::EMERGENCYPARSER);
 #endif
 
 #endif // ARDUINO_ARCH_SAM

Marlin/src/HAL/DUE/MarlinSerial.h

 #include <WString.h>
 
 #include "../../inc/MarlinConfigPre.h"
-
-#define DEC 10
-#define HEX 16
-#define OCT 8
-#define BIN 2
+#include "../../core/serial_hook.h"
 
 // Define constants and variables for buffering incoming serial data.  We're
 // using a ring buffer (I think), in which rx_buffer_head is the index of the
   static int read();
   static void flush();
   static ring_buffer_pos_t available();
-  static void write(const uint8_t c);
+  static size_t write(const uint8_t c);
   static void flushTX();
 
   static inline bool emergency_parser_enabled() { return Cfg::EMERGENCYPARSER; }
   FORCE_INLINE static uint8_t buffer_overruns() { return Cfg::RX_OVERRUNS ? rx_buffer_overruns : 0; }
   FORCE_INLINE static uint8_t framing_errors() { return Cfg::RX_FRAMING_ERRORS ? rx_framing_errors : 0; }
   FORCE_INLINE static ring_buffer_pos_t rxMaxEnqueued() { return Cfg::MAX_RX_QUEUED ? rx_max_enqueued : 0; }
-
-  FORCE_INLINE static void write(const char* str) { while (*str) write(*str++); }
-  FORCE_INLINE static void write(const uint8_t* buffer, size_t size) { while (size--) write(*buffer++); }
-  FORCE_INLINE static void print(const String& s) { for (int i = 0; i < (int)s.length(); i++) write(s[i]); }
-  FORCE_INLINE static void print(const char* str) { write(str); }
-
-  static void print(char, int = 0);
-  static void print(unsigned char, int = 0);
-  static void print(int, int = DEC);
-  static void print(unsigned int, int = DEC);
-  static void print(long, int = DEC);
-  static void print(unsigned long, int = DEC);
-  static void print(double, int = 2);
-
-  static void println(const String& s);
-  static void println(const char[]);
-  static void println(char, int = 0);
-  static void println(unsigned char, int = 0);
-  static void println(int, int = DEC);
-  static void println(unsigned int, int = DEC);
-  static void println(long, int = DEC);
-  static void println(unsigned long, int = DEC);
-  static void println(double, int = 2);
-  static void println();
-  operator bool() { return true; }
-
-private:
-  static void printNumber(unsigned long, const uint8_t);
-  static void printFloat(double, uint8_t);
 };
 
 // Serial port configuration
 };
 
 #if SERIAL_PORT >= 0
-  extern MarlinSerial<MarlinSerialCfg<SERIAL_PORT>> customizedSerial1;
+  typedef Serial0Type< MarlinSerial< MarlinSerialCfg<SERIAL_PORT> > > MSerialT;
+  extern MSerialT customizedSerial1;
 #endif
 
 #if defined(SERIAL_PORT_2) && SERIAL_PORT_2 >= 0
-  extern MarlinSerial<MarlinSerialCfg<SERIAL_PORT_2>> customizedSerial2;
+  typedef Serial0Type< MarlinSerial< MarlinSerialCfg<SERIAL_PORT_2> > > MSerialT2;
+  extern MSerialT2 customizedSerial2;
 #endif

Marlin/src/HAL/DUE/MarlinSerialUSB.cpp

 // Pending character
 static int pending_char = -1;
 
-#if ENABLED(EMERGENCY_PARSER)
-  static EmergencyParser::State emergency_state; // = EP_RESET
-#endif
-
 // Public Methods
 void MarlinSerialUSB::begin(const long) {}
 
 void MarlinSerialUSB::flush() { }
 void MarlinSerialUSB::flushTX() { }
 
-void MarlinSerialUSB::write(const uint8_t c) {
+size_t MarlinSerialUSB::write(const uint8_t c) {
 
   /* Do not even bother sending anything if USB CDC is not enumerated
      or not configured on the PC side or there is no program on the PC
      listening to our messages */
   if (!usb_task_cdc_isenabled() || !usb_task_cdc_dtr_active())
-    return;
+    return 0;
 
   /* Wait until the PC has read the pending to be sent data */
   while (usb_task_cdc_isenabled() &&
      or not configured on the PC side or there is no program on the PC
      listening to our messages at this point */
   if (!usb_task_cdc_isenabled() || !usb_task_cdc_dtr_active())
-    return;
+    return 0;
 
   // Fifo full
   //  udi_cdc_signal_overrun();
   udi_cdc_putc(c);
-}
-
-/**
- * Imports from print.h
- */
-
-void MarlinSerialUSB::print(char c, int base) {
-  print((long)c, base);
-}
-
-void MarlinSerialUSB::print(unsigned char b, int base) {
-  print((unsigned long)b, base);
-}
-
-void MarlinSerialUSB::print(int n, int base) {
-  print((long)n, base);
-}
-
-void MarlinSerialUSB::print(unsigned int n, int base) {
-  print((unsigned long)n, base);
-}
-
-void MarlinSerialUSB::print(long n, int base) {
-  if (base == 0)
-    write(n);
-  else if (base == 10) {
-    if (n < 0) {
-      print('-');
-      n = -n;
-    }
-    printNumber(n, 10);
-  }
-  else
-    printNumber(n, base);
-}
-
-void MarlinSerialUSB::print(unsigned long n, int base) {
-  if (base == 0) write(n);
-  else printNumber(n, base);
-}
-
-void MarlinSerialUSB::print(double n, int digits) {
-  printFloat(n, digits);
-}
-
-void MarlinSerialUSB::println() {
-  print('\r');
-  print('\n');
-}
-
-void MarlinSerialUSB::println(const String& s) {
-  print(s);
-  println();
-}
-
-void MarlinSerialUSB::println(const char c[]) {
-  print(c);
-  println();
-}
-
-void MarlinSerialUSB::println(char c, int base) {
-  print(c, base);
-  println();
-}
-
-void MarlinSerialUSB::println(unsigned char b, int base) {
-  print(b, base);
-  println();
-}
-
-void MarlinSerialUSB::println(int n, int base) {
-  print(n, base);
-  println();
-}
-
-void MarlinSerialUSB::println(unsigned int n, int base) {
-  print(n, base);
-  println();
-}
-
-void MarlinSerialUSB::println(long n, int base) {
-  print(n, base);
-  println();
-}
-
-void MarlinSerialUSB::println(unsigned long n, int base) {
-  print(n, base);
-  println();
-}
-
-void MarlinSerialUSB::println(double n, int digits) {
-  print(n, digits);
-  println();
-}
-
-// Private Methods
-
-void MarlinSerialUSB::printNumber(unsigned long n, uint8_t base) {
-  if (n) {
-    unsigned char buf[8 * sizeof(long)]; // Enough space for base 2
-    int8_t i = 0;
-    while (n) {
-      buf[i++] = n % base;
-      n /= base;
-    }
-    while (i--)
-      print((char)(buf[i] + (buf[i] < 10 ? '0' : 'A' - 10)));
-  }
-  else
-    print('0');
-}
-
-void MarlinSerialUSB::printFloat(double number, uint8_t digits) {
-  // Handle negative numbers
-  if (number < 0.0) {
-    print('-');
-    number = -number;
-  }
-
-  // Round correctly so that print(1.999, 2) prints as "2.00"
-  double rounding = 0.5;
-  LOOP_L_N(i, digits)
-    rounding *= 0.1;
-
-  number += rounding;
-
-  // Extract the integer part of the number and print it
-  unsigned long int_part = (unsigned long)number;
-  double remainder = number - (double)int_part;
-  print(int_part);
-
-  // Print the decimal point, but only if there are digits beyond
-  if (digits) {
-    print('.');
-    // Extract digits from the remainder one at a time
-    while (digits--) {
-      remainder *= 10.0;
-      int toPrint = int(remainder);
-      print(toPrint);
-      remainder -= toPrint;
-    }
-  }
+  return 1;
 }
 
 // Preinstantiate
 #if SERIAL_PORT == -1
-  MarlinSerialUSB customizedSerial1;
+  MSerialT customizedSerial1(TERN0(EMERGENCY_PARSER, true));
 #endif
 #if SERIAL_PORT_2 == -1
-  MarlinSerialUSB customizedSerial2;
+  MSerialT customizedSerial2(TERN0(EMERGENCY_PARSER, true));
 #endif
 
 #endif // HAS_USB_SERIAL

Marlin/src/HAL/DUE/MarlinSerialUSB.h

  */
 
 #include "../../inc/MarlinConfig.h"
-
 #if HAS_USB_SERIAL
 
 #include <WString.h>
+#include "../../core/serial_hook.h"
 
-#define DEC 10
-#define HEX 16
-#define OCT 8
-#define BIN 2
-
-class MarlinSerialUSB {
 
-public:
-  MarlinSerialUSB() {};
+struct MarlinSerialUSB {
   static void begin(const long);
   static void end();
   static int peek();
   static void flush();
   static void flushTX();
   static bool available();
-  static void write(const uint8_t c);
+  static size_t write(const uint8_t c);
 
   #if ENABLED(SERIAL_STATS_DROPPED_RX)
     FORCE_INLINE static uint32_t dropped() { return 0; }
   #if ENABLED(SERIAL_STATS_MAX_RX_QUEUED)
     FORCE_INLINE static int rxMaxEnqueued() { return 0; }
   #endif
-
-  FORCE_INLINE static void write(const char* str) { while (*str) write(*str++); }
-  FORCE_INLINE static void write(const uint8_t* buffer, size_t size) { while (size--) write(*buffer++); }
-  FORCE_INLINE static void print(const String& s) { for (int i = 0; i < (int)s.length(); i++) write(s[i]); }
-  FORCE_INLINE static void print(const char* str) { write(str); }
-
-  static void print(char, int = 0);
-  static void print(unsigned char, int = 0);
-  static void print(int, int = DEC);
-  static void print(unsigned int, int = DEC);
-  static void print(long, int = DEC);
-  static void print(unsigned long, int = DEC);
-  static void print(double, int = 2);
-
-  static void println(const String& s);
-  static void println(const char[]);
-  static void println(char, int = 0);
-  static void println(unsigned char, int = 0);
-  static void println(int, int = DEC);
-  static void println(unsigned int, int = DEC);
-  static void println(long, int = DEC);
-  static void println(unsigned long, int = DEC);
-  static void println(double, int = 2);
-  static void println();
-  operator bool() { return true; }
-
-private:
-  static void printNumber(unsigned long, const uint8_t);
-  static void printFloat(double, uint8_t);
 };
+typedef Serial0Type<MarlinSerialUSB> MSerialT;
 
 #if SERIAL_PORT == -1
-  extern MarlinSerialUSB customizedSerial1;
+  extern MSerialT customizedSerial1;
 #endif
 
 #if SERIAL_PORT_2 == -1
-  extern MarlinSerialUSB customizedSerial2;
+  extern MSerialT customizedSerial2;
 #endif
 
 #endif // HAS_USB_SERIAL

Marlin/src/HAL/DUE/usb/sd_mmc_spi_mem.cpp

   {
     char buffer[80];
     sprintf_P(buffer, PSTR("SDRD: %d @ 0x%08x\n"), nb_sector, addr);
-    PORT_REDIRECT(0);
+    PORT_REDIRECT(SERIAL_PORTMASK(0));
     SERIAL_ECHO(buffer);
   }
   #endif
   {
     char buffer[80];
     sprintf_P(buffer, PSTR("SDWR: %d @ 0x%08x\n"), nb_sector, addr);
-    PORT_REDIRECT(0);
+    PORT_REDIRECT(SERIAL_PORTMASK(0));
     SERIAL_ECHO(buffer);
   }
   #endif

Marlin/src/HAL/ESP32/FlushableHardwareSerial.cpp

 
 #ifdef ARDUINO_ARCH_ESP32
 
-FlushableHardwareSerial::FlushableHardwareSerial(int uart_nr)
-    : HardwareSerial(uart_nr)
-{}
 
-FlushableHardwareSerial flushableSerial(0);
+Serial0Type<FlushableHardwareSerial> flushableSerial(false, 0);
 
 #endif // ARDUINO_ARCH_ESP32

Marlin/src/HAL/ESP32/FlushableHardwareSerial.h

 #ifdef ARDUINO_ARCH_ESP32
 
 #include <HardwareSerial.h>
+#include "../../core/serial_hook.h"
 
 class FlushableHardwareSerial : public HardwareSerial {
 public:
-  FlushableHardwareSerial(int uart_nr);
-
-  inline void flushTX() { /* No need to flush the hardware serial, but defined here for compatibility. */ }
+  FlushableHardwareSerial(int uart_nr) : HardwareSerial(uart_nr) {}
 };
 
-extern FlushableHardwareSerial flushableSerial;
+extern Serial0Type<FlushableHardwareSerial> flushableSerial;
 
 #endif // ARDUINO_ARCH_ESP32

Marlin/src/HAL/ESP32/HAL.cpp

   #endif
 #endif
 
+#if ENABLED(ESP3D_WIFISUPPORT)
+  DefaultSerial MSerial(false, Serial2Socket);
+#endif
+
 // ------------------------
 // Externs
 // ------------------------

Marlin/src/HAL/ESP32/HAL.h

 
 #if EITHER(WIFISUPPORT, ESP3D_WIFISUPPORT)
   #if ENABLED(ESP3D_WIFISUPPORT)
-    #define MYSERIAL1 Serial2Socket
+    typedef ForwardSerial0Type< decltype(Serial2Socket) > DefaultSerial;
+    extern DefaultSerial MSerial;
+    #define MYSERIAL1 MSerial
   #else
     #define MYSERIAL1 webSocketSerial
   #endif

Marlin/src/HAL/ESP32/WebSocketSerial.cpp

 #include "wifi.h"
 #include <ESPAsyncWebServer.h>
 
-WebSocketSerial webSocketSerial;
+MSerialT webSocketSerial(false);
 AsyncWebSocket ws("/ws"); // TODO Move inside the class.
 
 // RingBuffer impl
   return written;
 }
 
-void WebSocketSerial::flushTX() {
-  // No need to do anything as there's no benefit to sending partial lines over the websocket connection.
-}
-
 #endif // WIFISUPPORT
 #endif // ARDUINO_ARCH_ESP32

Marlin/src/HAL/ESP32/WebSocketSerial.h

 #pragma once
 
 #include "../../inc/MarlinConfig.h"
+#include "../../core/serial_hook.h"
 
 #include <Stream.h>
 
   int peek();
   int read();
   void flush();
-  void flushTX();
   size_t write(const uint8_t c);
   size_t write(const uint8_t* buffer, size_t size);
 
-  operator bool() { return true; }
-
   #if ENABLED(SERIAL_STATS_DROPPED_RX)
     FORCE_INLINE uint32_t dropped() { return 0; }
   #endif
   #endif
 };
 
-extern WebSocketSerial webSocketSerial;
+typedef Serial0Type<WebSocketSerial> MSerialT;
+extern MSerialT webSocketSerial;

Marlin/src/HAL/LINUX/HAL.cpp

 #include "../../inc/MarlinConfig.h"
 #include "../shared/Delay.h"
 
-HalSerial usb_serial;
+MSerialT usb_serial(TERN0(EMERGENCY_PARSER, true));
 
 // U8glib required functions
 extern "C" {

Marlin/src/HAL/LINUX/HAL.h

 
 #define SHARED_SERVOS HAS_SERVOS
 
-extern HalSerial usb_serial;
+extern MSerialT usb_serial;
 #define MYSERIAL0 usb_serial
 
 #define ST7920_DELAY_1 DELAY_NS(600)

Marlin/src/HAL/LINUX/include/serial.h

 #if ENABLED(EMERGENCY_PARSER)
   #include "../../../feature/e_parser.h"
 #endif
+#include "../../../core/serial_hook.h"
 
 #include <stdarg.h>
 #include <stdio.h>
   volatile uint32_t index_read;
 };
 
-class HalSerial {
-public:
-
-  #if ENABLED(EMERGENCY_PARSER)
-    EmergencyParser::State emergency_state;
-    static inline bool emergency_parser_enabled() { return true; }
-  #endif
-
+struct HalSerial {
   HalSerial() { host_connected = true; }
 
   void begin(int32_t) {}
-
-  void end() {}
+  void end()          {}
 
   int peek() {
     uint8_t value;
     return transmit_buffer.write(c);
   }
 
-  operator bool() { return host_connected; }
+  bool connected() { return host_connected; }
 
   uint16_t available() {
     return (uint16_t)receive_buffer.available();
       while (transmit_buffer.available()) { /* nada */ }
   }
 
-  void printf(const char *format, ...) {
-    static char buffer[256];
-    va_list vArgs;
-    va_start(vArgs, format);
-    int length = vsnprintf((char *) buffer, 256, (char const *) format, vArgs);
-    va_end(vArgs);
-    if (length > 0 && length < 256) {
-      if (host_connected) {
-        for (int i = 0; i < length;) {
-          if (transmit_buffer.write(buffer[i])) {
-            ++i;
-          }
-        }
-      }
-    }
-  }
-
-  #define DEC 10
-  #define HEX 16
-  #define OCT 8
-  #define BIN 2
-
-  void print_bin(uint32_t value, uint8_t num_digits) {
-    uint32_t mask = 1 << (num_digits -1);
-    for (uint8_t i = 0; i < num_digits; i++) {
-      if (!(i %  4) && i) write(' ');
-      if (!(i % 16) && i) write(' ');
-      if (value & mask)   write('1');
-      else                write('0');
-      value <<= 1;
-    }
-  }
-
-  void print(const char value[]) { printf("%s" , value); }
-  void print(char value, int nbase = 0) {
-    if (nbase == BIN) print_bin(value, 8);
-    else if (nbase == OCT) printf("%3o", value);
-    else if (nbase == HEX) printf("%2X", value);
-    else if (nbase == DEC ) printf("%d", value);
-    else printf("%c" , value);
-  }
-  void print(unsigned char value, int nbase = 0) {
-    if (nbase == BIN) print_bin(value, 8);
-    else if (nbase == OCT) printf("%3o", value);
-    else if (nbase == HEX) printf("%2X", value);
-    else printf("%u" , value);
-  }
-  void print(int value, int nbase = 0) {
-    if (nbase == BIN) print_bin(value, 16);
-    else if (nbase == OCT) printf("%6o", value);
-    else if (nbase == HEX) printf("%4X", value);
-    else printf("%d", value);
-  }
-  void print(unsigned int value, int nbase = 0) {
-    if (nbase == BIN) print_bin(value, 16);
-    else if (nbase == OCT) printf("%6o", value);
-    else if (nbase == HEX) printf("%4X", value);
-    else printf("%u" , value);
-  }
-  void print(long value, int nbase = 0) {
-    if (nbase == BIN) print_bin(value, 32);
-    else if (nbase == OCT) printf("%11o", value);
-    else if (nbase == HEX) printf("%8X", value);
-    else printf("%ld" , value);
-  }
-  void print(unsigned long value, int nbase = 0) {
-    if (nbase == BIN) print_bin(value, 32);
-    else if (nbase == OCT) printf("%11o", value);
-    else if (nbase == HEX) printf("%8X", value);
-    else printf("%lu" , value);
-  }
-  void print(float value, int round = 6)  { printf("%f" , value); }
-  void print(double value, int round = 6) { printf("%f" , value); }
-
-  void println(const char value[]) { printf("%s\n" , value); }
-  void println(char value, int nbase = 0) { print(value, nbase); println(); }
-  void println(unsigned char value, int nbase = 0) { print(value, nbase); println(); }
-  void println(int value, int nbase = 0) { print(value, nbase); println(); }
-  void println(unsigned int value, int nbase = 0) { print(value, nbase); println(); }
-  void println(long value, int nbase = 0) { print(value, nbase); println(); }
-  void println(unsigned long value, int nbase = 0) { print(value, nbase); println(); }
-  void println(float value, int round = 6) { printf("%f\n" , value); }
-  void println(double value, int round = 6) { printf("%f\n" , value); }
-  void println() { print('\n'); }
-
   volatile RingBuffer<uint8_t, 128> receive_buffer;
   volatile RingBuffer<uint8_t, 128> transmit_buffer;
   volatile bool host_connected;
 };
+
+typedef Serial0Type<HalSerial> MSerialT;

Marlin/src/HAL/LPC1768/HAL.cpp

   #include "watchdog.h"
 #endif
 
+DefaultSerial USBSerial(false, UsbSerial);
+
 uint32_t HAL_adc_reading = 0;
 
 // U8glib required functions

Marlin/src/HAL/LPC1768/HAL.h

   #define ST7920_DELAY_3 DELAY_NS(750)
 #endif
 
+typedef ForwardSerial0Type< decltype(UsbSerial) > DefaultSerial;
+extern DefaultSerial USBSerial;
+
 #define _MSERIAL(X) MSerial##X
 #define MSERIAL(X) _MSERIAL(X)
 #define MSerial0 MSerial
 
 #if SERIAL_PORT == -1
-  #define MYSERIAL0 UsbSerial
+  #define MYSERIAL0 USBSerial
 #elif WITHIN(SERIAL_PORT, 0, 3)
   #define MYSERIAL0 MSERIAL(SERIAL_PORT)
 #else
 
 #ifdef SERIAL_PORT_2
   #if SERIAL_PORT_2 == -1
-    #define MYSERIAL1 UsbSerial
+    #define MYSERIAL1 USBSerial
   #elif WITHIN(SERIAL_PORT_2, 0, 3)
     #define MYSERIAL1 MSERIAL(SERIAL_PORT_2)
   #else
 
 #ifdef MMU2_SERIAL_PORT
   #if MMU2_SERIAL_PORT == -1
-    #define MMU2_SERIAL UsbSerial
+    #define MMU2_SERIAL USBSerial
   #elif WITHIN(MMU2_SERIAL_PORT, 0, 3)
     #define MMU2_SERIAL MSERIAL(MMU2_SERIAL_PORT)
   #else
 
 #ifdef LCD_SERIAL_PORT
   #if LCD_SERIAL_PORT == -1
-    #define LCD_SERIAL UsbSerial
+    #define LCD_SERIAL USBSerial
   #elif WITHIN(LCD_SERIAL_PORT, 0, 3)
     #define LCD_SERIAL MSERIAL(LCD_SERIAL_PORT)
   #else

Marlin/src/HAL/LPC1768/MarlinSerial.cpp

 #include "MarlinSerial.h"
 
 #if USING_SERIAL_0
-  MarlinSerial MSerial(LPC_UART0);
+  MSerialT MSerial(true, LPC_UART0);
   extern "C" void UART0_IRQHandler() { MSerial.IRQHandler(); }
 #endif
 #if USING_SERIAL_1
-  MarlinSerial MSerial1((LPC_UART_TypeDef *) LPC_UART1);
+  MSerialT MSerial1(true, (LPC_UART_TypeDef *) LPC_UART1);
   extern "C" void UART1_IRQHandler() { MSerial1.IRQHandler(); }
 #endif
 #if USING_SERIAL_2
-  MarlinSerial MSerial2(LPC_UART2);
+  MSerialT MSerial2(true, LPC_UART2);
   extern "C" void UART2_IRQHandler() { MSerial2.IRQHandler(); }
 #endif
 #if USING_SERIAL_3
-  MarlinSerial MSerial3(LPC_UART3);
+  MSerialT MSerial3(true, LPC_UART3);
   extern "C" void UART3_IRQHandler() { MSerial3.IRQHandler(); }
 #endif
 

Marlin/src/HAL/LPC1768/MarlinSerial.h

 #if ENABLED(EMERGENCY_PARSER)
   #include "../../feature/e_parser.h"
 #endif
+#include "../../core/serial_hook.h"
 
 #ifndef SERIAL_PORT
   #define SERIAL_PORT 0
 
 class MarlinSerial : public HardwareSerial<RX_BUFFER_SIZE, TX_BUFFER_SIZE> {
 public:
-  MarlinSerial(LPC_UART_TypeDef *UARTx) :
-    HardwareSerial<RX_BUFFER_SIZE, TX_BUFFER_SIZE>(UARTx)
-    #if ENABLED(EMERGENCY_PARSER)
-      , emergency_state(EmergencyParser::State::EP_RESET)
-    #endif
-    { }
+  MarlinSerial(LPC_UART_TypeDef *UARTx) : HardwareSerial<RX_BUFFER_SIZE, TX_BUFFER_SIZE>(UARTx) { }
 
   void end() {}
 
   #if ENABLED(EMERGENCY_PARSER)
     bool recv_callback(const char c) override {
-      emergency_parser.update(emergency_state, c);
+      emergency_parser.update(static_cast<Serial0Type<MarlinSerial> *>(this)->emergency_state, c);
       return true; // do not discard character
     }
-
-    EmergencyParser::State emergency_state;
-    static inline bool emergency_parser_enabled() { return true; }
   #endif
 };
 
-extern MarlinSerial MSerial;
-extern MarlinSerial MSerial1;
-extern MarlinSerial MSerial2;
-extern MarlinSerial MSerial3;
+typedef Serial0Type<MarlinSerial> MSerialT;
+extern MSerialT MSerial;
+extern MSerialT MSerial1;
+extern MSerialT MSerial2;
+extern MSerialT MSerial3;

Marlin/src/HAL/SAMD51/HAL.cpp

 #include <Adafruit_ZeroDMA.h>
 #include <wiring_private.h>
 
+#ifdef ADAFRUIT_GRAND_CENTRAL_M4
+  DefaultSerial MSerial(false, Serial);
+  DefaultSerial1 MSerial1(false, Serial1);
+#endif
+
 // ------------------------
 // Local defines
 // ------------------------

Marlin/src/HAL/SAMD51/HAL.h

   #include "MarlinSerial_AGCM4.h"
 
   // Serial ports
+  typedef ForwardSerial0Type< decltype(Serial) > DefaultSerial;
+  extern DefaultSerial MSerial;
+  typedef ForwardSerial0Type< decltype(Serial1) > DefaultSerial1;
+  extern DefaultSerial1 MSerial1;
 
   // MYSERIAL0 required before MarlinSerial includes!
 
-  #define __MSERIAL(X) Serial##X
+  #define __MSERIAL(X) MSerial##X
   #define _MSERIAL(X) __MSERIAL(X)
   #define MSERIAL(X) _MSERIAL(INCREMENT(X))
 
   #if SERIAL_PORT == -1
-    #define MYSERIAL0 Serial
+    #define MYSERIAL0 MSerial
   #elif WITHIN(SERIAL_PORT, 0, 3)
     #define MYSERIAL0 MSERIAL(SERIAL_PORT)
   #else
 
   #ifdef SERIAL_PORT_2
     #if SERIAL_PORT_2 == -1
-      #define MYSERIAL1 Serial
+      #define MYSERIAL1 MSerial
     #elif WITHIN(SERIAL_PORT_2, 0, 3)
       #define MYSERIAL1 MSERIAL(SERIAL_PORT_2)
     #else
 
   #ifdef MMU2_SERIAL_PORT
     #if MMU2_SERIAL_PORT == -1
-      #define MMU2_SERIAL Serial
+      #define MMU2_SERIAL MSerial
     #elif WITHIN(MMU2_SERIAL_PORT, 0, 3)
       #define MMU2_SERIAL MSERIAL(MMU2_SERIAL_PORT)
     #else
 
   #ifdef LCD_SERIAL_PORT
     #if LCD_SERIAL_PORT == -1
-      #define LCD_SERIAL Serial
+      #define LCD_SERIAL MSerial
     #elif WITHIN(LCD_SERIAL_PORT, 0, 3)
       #define LCD_SERIAL MSERIAL(LCD_SERIAL_PORT)
     #else

Marlin/src/HAL/SAMD51/MarlinSerial_AGCM4.cpp

 #include "../../inc/MarlinConfig.h"
 
 #if USING_SERIAL_1
-  Uart Serial2(&sercom4, PIN_SERIAL2_RX, PIN_SERIAL2_TX, PAD_SERIAL2_RX, PAD_SERIAL2_TX);
+  UartT Serial2(false, &sercom4, PIN_SERIAL2_RX, PIN_SERIAL2_TX, PAD_SERIAL2_RX, PAD_SERIAL2_TX);
   void SERCOM4_0_Handler() { Serial2.IrqHandler(); }
   void SERCOM4_1_Handler() { Serial2.IrqHandler(); }
   void SERCOM4_2_Handler() { Serial2.IrqHandler(); }
 #endif
 
 #if USING_SERIAL_2
-  Uart Serial3(&sercom1, PIN_SERIAL3_RX, PIN_SERIAL3_TX, PAD_SERIAL3_RX, PAD_SERIAL3_TX);
+  UartT Serial3(false, &sercom1, PIN_SERIAL3_RX, PIN_SERIAL3_TX, PAD_SERIAL3_RX, PAD_SERIAL3_TX);
   void SERCOM1_0_Handler() { Serial3.IrqHandler(); }
   void SERCOM1_1_Handler() { Serial3.IrqHandler(); }
   void SERCOM1_2_Handler() { Serial3.IrqHandler(); }
 #endif
 
 #if USING_SERIAL_3
-  Uart Serial4(&sercom5, PIN_SERIAL4_RX, PIN_SERIAL4_TX, PAD_SERIAL4_RX, PAD_SERIAL4_TX);
+  UartT Serial4(false, &sercom5, PIN_SERIAL4_RX, PIN_SERIAL4_TX, PAD_SERIAL4_RX, PAD_SERIAL4_TX);
   void SERCOM5_0_Handler() { Serial4.IrqHandler(); }
   void SERCOM5_1_Handler() { Serial4.IrqHandler(); }
   void SERCOM5_2_Handler() { Serial4.IrqHandler(); }

Marlin/src/HAL/SAMD51/MarlinSerial_AGCM4.h

  */
 #pragma once
 
-extern Uart Serial2;
-extern Uart Serial3;
-extern Uart Serial4;
+#include "../../core/serial_hook.h"
+
+typedef Serial0Type<Uart> UartT;
+
+extern UartT Serial2;
+extern UartT Serial3;
+extern UartT Serial4;

Marlin/src/HAL/STM32/HAL.cpp

 #include "../../inc/MarlinConfig.h"
 #include "../shared/Delay.h"
 
+#ifdef USBCON
+  DefaultSerial MSerial(false, SerialUSB);
+#endif
+
 #if ENABLED(SRAM_EEPROM_EMULATION)
   #if STM32F7xx
     #include <stm32f7xx_ll_pwr.h>

Marlin/src/HAL/STM32/HAL.h

 
 #ifdef USBCON
   #include <USBSerial.h>
+  #include "../../core/serial_hook.h" 
+  typedef ForwardSerial0Type< decltype(SerialUSB) > DefaultSerial;
+  extern DefaultSerial MSerial;
 #endif
 
 // ------------------------
 #define MSERIAL(X) _MSERIAL(X)
 
 #if SERIAL_PORT == -1
-  #define MYSERIAL0 SerialUSB
+  #define MYSERIAL0 MSerial
 #elif WITHIN(SERIAL_PORT, 1, 6)
   #define MYSERIAL0 MSERIAL(SERIAL_PORT)
 #else
 
 #ifdef SERIAL_PORT_2
   #if SERIAL_PORT_2 == -1
-    #define MYSERIAL1 SerialUSB
+    #define MYSERIAL1 MSerial
   #elif WITHIN(SERIAL_PORT_2, 1, 6)
     #define MYSERIAL1 MSERIAL(SERIAL_PORT_2)
   #else
 
 #ifdef MMU2_SERIAL_PORT
   #if MMU2_SERIAL_PORT == -1
-    #define MMU2_SERIAL SerialUSB
+    #define MMU2_SERIAL MSerial
   #elif WITHIN(MMU2_SERIAL_PORT, 1, 6)
     #define MMU2_SERIAL MSERIAL(MMU2_SERIAL_PORT)
   #else
 
 #ifdef LCD_SERIAL_PORT
   #if LCD_SERIAL_PORT == -1
-    #define LCD_SERIAL SerialUSB
+    #define LCD_SERIAL MSerial
   #elif WITHIN(LCD_SERIAL_PORT, 1, 6)
     #define LCD_SERIAL MSERIAL(LCD_SERIAL_PORT)
   #else

Marlin/src/HAL/STM32/MarlinSerial.cpp

 
 #define DECLARE_SERIAL_PORT(ser_num) \
   void _rx_complete_irq_ ## ser_num (serial_t * obj); \
-  MarlinSerial MSerial ## ser_num (USART ## ser_num, &_rx_complete_irq_ ## ser_num); \
+  MSerialT MSerial ## ser_num (true, USART ## ser_num, &_rx_complete_irq_ ## ser_num); \
   void _rx_complete_irq_ ## ser_num (serial_t * obj) { MSerial ## ser_num ._rx_complete_irq(obj); }
 
 #define DECLARE_SERIAL_PORT_EXP(ser_num) DECLARE_SERIAL_PORT(ser_num)

Marlin/src/HAL/STM32/MarlinSerial.h

   #include "../../feature/e_parser.h"
 #endif
 
+#include "../../core/serial_hook.h"
+
 typedef void (*usart_rx_callback_t)(serial_t * obj);
 
-class MarlinSerial : public HardwareSerial {
-public:
+struct MarlinSerial : public HardwareSerial {
   MarlinSerial(void* peripheral, usart_rx_callback_t rx_callback) :
       HardwareSerial(peripheral), _rx_callback(rx_callback)
-      #if ENABLED(EMERGENCY_PARSER)
-        , emergency_state(EmergencyParser::State::EP_RESET)
-      #endif
   { }
 
-  #if ENABLED(EMERGENCY_PARSER)
-    static inline bool emergency_parser_enabled() { return true; }
-  #endif
-
   void begin(unsigned long baud, uint8_t config);
   inline void begin(unsigned long baud) { begin(baud, SERIAL_8N1); }
 
 
 protected:
   usart_rx_callback_t _rx_callback;
-  #if ENABLED(EMERGENCY_PARSER)
-    EmergencyParser::State emergency_state;
-  #endif
 };
 
-extern MarlinSerial MSerial1;
-extern MarlinSerial MSerial2;
-extern MarlinSerial MSerial3;
-extern MarlinSerial MSerial4;
-extern MarlinSerial MSerial5;
-extern MarlinSerial MSerial6;
-extern MarlinSerial MSerial7;
-extern MarlinSerial MSerial8;
-extern MarlinSerial MSerial9;
-extern MarlinSerial MSerial10;
-extern MarlinSerial MSerialLP1;
+typedef Serial0Type<MarlinSerial> MSerialT;
+extern MSerialT MSerial1;
+extern MSerialT MSerial2;
+extern MSerialT MSerial3;
+extern MSerialT MSerial4;
+extern MSerialT MSerial5;
+extern MSerialT MSerial6;
+extern MSerialT MSerial7;
+extern MSerialT MSerial8;
+extern MSerialT MSerial9;
+extern MSerialT MSerial10;
+extern MSerialT MSerialLP1;

Marlin/src/HAL/STM32F1/HAL.cpp

 
 #if defined(SERIAL_USB) && !HAS_SD_HOST_DRIVE
   USBSerial SerialUSB;
+  DefaultSerial MSerial(false, SerialUSB);
 #endif
 
 uint16_t HAL_adc_result;

Marlin/src/HAL/STM32F1/HAL.h

 #endif
 
 #ifdef SERIAL_USB
+  typedef ForwardSerial0Type< USBSerial > DefaultSerial;
+  extern DefaultSerial MSerial;
+
   #if !HAS_SD_HOST_DRIVE
-    #define UsbSerial Serial
+    #define UsbSerial MSerial
   #else
     #define UsbSerial MarlinCompositeSerial
   #endif

Marlin/src/HAL/STM32F1/MarlinSerial.cpp

 
 // Copied from ~/.platformio/packages/framework-arduinoststm32-maple/STM32F1/system/libmaple/usart_private.h
 // Changed to handle Emergency Parser
-static inline __always_inline void my_usart_irq(ring_buffer *rb, ring_buffer *wb, usart_reg_map *regs, MarlinSerial &serial) {
+static inline __always_inline void my_usart_irq(ring_buffer *rb, ring_buffer *wb, usart_reg_map *regs, MSerialT &serial) {
  /* Handle RXNEIE and TXEIE interrupts.
   * RXNE signifies availability of a byte in DR.
   *
   ;
 }
 
-#define DEFINE_HWSERIAL_MARLIN(name, n)   \
-  MarlinSerial name(USART##n,             \
-            BOARD_USART##n##_TX_PIN,      \
-            BOARD_USART##n##_RX_PIN,      \
-            serial_handles_emergency(n)); \
-  extern "C" void __irq_usart##n(void) {  \
+#define DEFINE_HWSERIAL_MARLIN(name, n)     \
+  MSerialT name(serial_handles_emergency(n),\
+            USART##n,                       \
+            BOARD_USART##n##_TX_PIN,        \
+            BOARD_USART##n##_RX_PIN);       \
+  extern "C" void __irq_usart##n(void) {    \
     my_usart_irq(USART##n->rb, USART##n->wb, USART##n##_BASE, MSerial##n); \
   }
 
 #define DEFINE_HWSERIAL_UART_MARLIN(name, n) \
-  MarlinSerial name(UART##n,                 \
+  MSerialT name(serial_handles_emergency(n), \
+          UART##n,                           \
           BOARD_USART##n##_TX_PIN,           \
-          BOARD_USART##n##_RX_PIN,           \
-          serial_handles_emergency(n));      \
+          BOARD_USART##n##_RX_PIN);          \
   extern "C" void __irq_usart##n(void) {     \
     my_usart_irq(UART##n->rb, UART##n->wb, UART##n##_BASE, MSerial##n); \
   }

Marlin/src/HAL/STM32F1/MarlinSerial.h

 #include <WString.h>
 
 #include "../../inc/MarlinConfigPre.h"
-#if ENABLED(EMERGENCY_PARSER)
-  #include "../../feature/e_parser.h"
-#endif
+#include "../../core/serial_hook.h"
 
 // Increase priority of serial interrupts, to reduce overflow errors
 #define UART_IRQ_PRIO 1
 
-class MarlinSerial : public HardwareSerial {
-public:
-  #if ENABLED(EMERGENCY_PARSER)
-    const bool ep_enabled;
-    EmergencyParser::State emergency_state;
-    inline bool emergency_parser_enabled() { return ep_enabled; }
-  #endif
-
-  MarlinSerial(struct usart_dev *usart_device, uint8 tx_pin, uint8 rx_pin, bool TERN_(EMERGENCY_PARSER, ep_capable)) :
-    HardwareSerial(usart_device, tx_pin, rx_pin)
-    #if ENABLED(EMERGENCY_PARSER)
-      , ep_enabled(ep_capable)
-      , emergency_state(EmergencyParser::State::EP_RESET)
-    #endif
-    { }
+struct MarlinSerial : public HardwareSerial {
+  MarlinSerial(struct usart_dev *usart_device, uint8 tx_pin, uint8 rx_pin) : HardwareSerial(usart_device, tx_pin, rx_pin) { }
 
   #ifdef UART_IRQ_PRIO
     // Shadow the parent methods to set IRQ priority after begin()
   #endif
 };
 
-extern MarlinSerial MSerial1;
-extern MarlinSerial MSerial2;
-extern MarlinSerial MSerial3;
+typedef Serial0Type<MarlinSerial> MSerialT;
+
+extern MSerialT MSerial1;
+extern MSerialT MSerial2;
+extern MSerialT MSerial3;
 #if EITHER(STM32_HIGH_DENSITY, STM32_XL_DENSITY)
-  extern MarlinSerial MSerial4;
-  extern MarlinSerial MSerial5;
+  extern MSerialT MSerial4;
+  extern MSerialT MSerial5;
 #endif

Marlin/src/HAL/STM32F1/msc_sd.cpp

 #define PRODUCT_ID 0x29
 
 USBMassStorage MarlinMSC;
-MarlinUSBCompositeSerial MarlinCompositeSerial;
+Serial0Type<USBCompositeSerial> MarlinCompositeSerial(true);
 
 #include "../../inc/MarlinConfig.h"
 

Marlin/src/HAL/STM32F1/msc_sd.h

 #include <USBComposite.h>
 
 #include "../../inc/MarlinConfigPre.h"
-#if ENABLED(EMERGENCY_PARSER)
-  #include "../../feature/e_parser.h"
-#endif
-
-class MarlinUSBCompositeSerial : public USBCompositeSerial {
-public:
-  MarlinUSBCompositeSerial() : USBCompositeSerial()
-    #if ENABLED(EMERGENCY_PARSER)
-      , emergency_state(EmergencyParser::State::EP_RESET)
-    #endif
-    { }
-
-  #if ENABLED(EMERGENCY_PARSER)
-    EmergencyParser::State emergency_state;
-    inline bool emergency_parser_enabled() { return true; }
-  #endif
-};
+#include "../../core/serial_hook.h"
 
 extern USBMassStorage MarlinMSC;
-extern MarlinUSBCompositeSerial MarlinCompositeSerial;
+extern Serial0Type<USBCompositeSerial> MarlinCompositeSerial;
 
 void MSC_SD_init();

Marlin/src/HAL/TEENSY31_32/HAL.cpp

 
 #include <Wire.h>
 
+DefaultSerial MSerial(false);
+USBSerialType USBSerial(false, SerialUSB);
+
 uint16_t HAL_adc_result;
 
 static const uint8_t pin2sc1a[] = {

Marlin/src/HAL/TEENSY31_32/HAL.h

   #define IS_TEENSY32 1
 #endif
 
-#define _MSERIAL(X) Serial##X
+#include "../../core/serial_hook.h"
+typedef Serial0Type<decltype(Serial)> DefaultSerial;
+extern DefaultSerial MSerial;
+typedef ForwardSerial0Type<decltype(SerialUSB)> USBSerialType;
+extern USBSerialType USBSerial;
+
+#define _MSERIAL(X) MSerial##X
 #define MSERIAL(X) _MSERIAL(X)
-#define Serial0 Serial
+#define MSerial0 MSerial
 
 #if SERIAL_PORT == -1
-  #define MYSERIAL0 SerialUSB
+  #define MYSERIAL0 USBSerial
 #elif WITHIN(SERIAL_PORT, 0, 3)
   #define MYSERIAL0 MSERIAL(SERIAL_PORT)
 #endif

Marlin/src/HAL/TEENSY35_36/HAL.cpp

 
 #include <Wire.h>
 
+DefaultSerial MSerial(false);
+USBSerialType USBSerial(false, SerialUSB);
+
 uint16_t HAL_adc_result, HAL_adc_select;
 
 static const uint8_t pin2sc1a[] = {

Marlin/src/HAL/TEENSY35_36/HAL.h

   #define IS_TEENSY35 1
 #endif
 
-#define _MSERIAL(X) Serial##X
+#include "../../core/serial_hook.h"
+typedef Serial0Type<decltype(Serial)> DefaultSerial;
+extern DefaultSerial MSerial;
+typedef ForwardSerial0Type<decltype(SerialUSB)> USBSerialType;
+extern USBSerialType USBSerial;
+
+#define _MSERIAL(X) MSerial##X
 #define MSERIAL(X) _MSERIAL(X)
-#define Serial0 Serial
+#define MSerial0 MSerial
 
 #if SERIAL_PORT == -1
-  #define MYSERIAL0 SerialUSB
+  #define MYSERIAL0 USBSerial
 #elif WITHIN(SERIAL_PORT, 0, 3)
   #define MYSERIAL0 MSERIAL(SERIAL_PORT)
 #endif

Marlin/src/HAL/TEENSY40_41/HAL.cpp

 
 #include <Wire.h>
 
+DefaultSerial MSerial(false);
+USBSerialType USBSerial(false, SerialUSB);
+
 uint16_t HAL_adc_result, HAL_adc_select;
 
 static const uint8_t pin2sc1a[] = {

Marlin/src/HAL/TEENSY40_41/HAL.h

 #include <stdint.h>
 #include <util/atomic.h>
 
+#if HAS_ETHERNET
+  #include "../../feature/ethernet.h"
+#endif
+
 //#define ST7920_DELAY_1 DELAY_NS(600)
 //#define ST7920_DELAY_2 DELAY_NS(750)
 //#define ST7920_DELAY_3 DELAY_NS(750)
   #define IS_TEENSY41 1
 #endif
 
-#define _MSERIAL(X) Serial##X
+#include "../../core/serial_hook.h"
+typedef Serial0Type<decltype(Serial)> DefaultSerial;
+extern DefaultSerial MSerial;
+typedef ForwardSerial0Type<decltype(SerialUSB)> USBSerialType;
+extern USBSerialType USBSerial;
+
+#define _MSERIAL(X) MSerial##X
 #define MSERIAL(X) _MSERIAL(X)
-#define Serial0 Serial
+#define MSerial0 MSerial
 
 #if SERIAL_PORT == -1
   #define MYSERIAL0 SerialUSB

Marlin/src/MarlinCore.cpp

 
   MYSERIAL0.begin(BAUDRATE);
   millis_t serial_connect_timeout = millis() + 1000UL;
-  while (!MYSERIAL0 && PENDING(millis(), serial_connect_timeout)) { /*nada*/ }
+  while (!MYSERIAL0.connected() && PENDING(millis(), serial_connect_timeout)) { /*nada*/ }
 
   #if HAS_MULTI_SERIAL && !HAS_ETHERNET
     MYSERIAL1.begin(BAUDRATE);
     serial_connect_timeout = millis() + 1000UL;
-    while (!MYSERIAL1 && PENDING(millis(), serial_connect_timeout)) { /*nada*/ }
+    while (!MYSERIAL1.connected() && PENDING(millis(), serial_connect_timeout)) { /*nada*/ }
   #endif
   SERIAL_ECHOLNPGM("start");
 

Marlin/src/core/macros.h

 
   #endif
 
+  // C++11 solution that is standard compliant. <type_traits> is not available on all platform
+  namespace Private {
+    template<bool, typename _Tp = void> struct enable_if { };
+    template<typename _Tp>              struct enable_if<true, _Tp> { typedef _Tp type; };
+  }
+  // C++11 solution using SFINAE to detect the existance of a member in a class at compile time. 
+  // It creates a HasMember<Type> structure containing 'value' set to true if the member exists  
+  #define HAS_MEMBER_IMPL(Member) \
+    namespace Private { \
+      template <typename Type, typename Yes=char, typename No=long> struct HasMember_ ## Member { \
+        template <typename C> static Yes& test( decltype(&C::Member) ) ; \
+        template <typename C> static No& test(...); \
+        enum { value = sizeof(test<Type>(0)) == sizeof(Yes) }; }; \
+    }
+
+  // Call the method if it exists, but do nothing if it does not. The method is detected at compile time.
+  // If the method exists, this is inlined and does not cost anything. Else, an "empty" wrapper is created, returning a default value
+  #define CALL_IF_EXISTS_IMPL(Return, Method, ...) \
+    HAS_MEMBER_IMPL(Method) \
+    namespace Private { \
+      template <typename T, typename ... Args> FORCE_INLINE typename enable_if<HasMember_ ## Method <T>::value, Return>::type Call_ ## Method(T * t, Args... a) { return static_cast<Return>(t->Method(a...)); } \
+                                                      _UNUSED static                                                  Return  Call_ ## Method(...) { return __VA_ARGS__; } \
+    }
+  #define CALL_IF_EXISTS(Return, That, Method, ...) \
+    static_cast<Return>(Private::Call_ ## Method(That, ##__VA_ARGS__))
+
 #else
 
   #define MIN_2(a,b)      ((a)<(b)?(a):(b))

Marlin/src/core/serial.cpp

 #include "serial.h"
 #include "../inc/MarlinConfig.h"
 
+#if HAS_ETHERNET
+  #include "../feature/ethernet.h"
+#endif
+
 uint8_t marlin_debug_flags = MARLIN_DEBUG_NONE;
 
 // Commonly-used strings in serial output
 PGMSTR(SP_X_LBL, " X:"); PGMSTR(SP_Y_LBL, " Y:"); PGMSTR(SP_Z_LBL, " Z:"); PGMSTR(SP_E_LBL, " E:");
 
 #if HAS_MULTI_SERIAL
-  serial_index_t serial_port_index = 0;
+  #ifdef SERIAL_CATCHALL
+    SerialOutputT multiSerial(MYSERIAL, SERIAL_CATCHALL);
+  #else
+    #if HAS_ETHERNET
+      // Runtime checking of the condition variable
+      ConditionalSerial<decltype(MYSERIAL1)> serialOut1(ethernet.have_telnet_client, MYSERIAL1, false); // Takes reference here
+    #else
+      // Don't pay for runtime checking a true variable, instead use the output directly
+      #define serialOut1 MYSERIAL1
+    #endif
+    SerialOutputT multiSerial(MYSERIAL0, serialOut1);
+  #endif
 #endif
 
 void serialprintPGM(PGM_P str) {

Marlin/src/core/serial.h

 #pragma once
 
 #include "../inc/MarlinConfig.h"
-
-#if HAS_ETHERNET
-  #include "../feature/ethernet.h"
-#endif
+#include "serial_hook.h"
 
 // Commonly-used strings in serial output
 extern const char NUL_STR[], SP_P_STR[], SP_T_STR[],
 // Serial redirection
 //
 typedef int8_t serial_index_t;
-#define SERIAL_BOTH 0x7F
-
+#define SERIAL_ALL 0x7F
 #if HAS_MULTI_SERIAL
-  extern serial_index_t serial_port_index;
-  #define _PORT_REDIRECT(n,p)   REMEMBER(n,serial_port_index,p)
-  #define _PORT_RESTORE(n)      RESTORE(n)
-
+  #define _PORT_REDIRECT(n,p)   REMEMBER(n,multiSerial.portMask,p)
+  #define SERIAL_ASSERT(P)      if(multiSerial.portMask!=(P)){ debugger(); }
   #ifdef SERIAL_CATCHALL
-    #define SERIAL_OUT(WHAT, V...) (void)CAT(MYSERIAL,SERIAL_CATCHALL).WHAT(V)
+    typedef MultiSerial<decltype(MYSERIAL), decltype(SERIAL_CATCHALL), 0> SerialOutputT;
   #else
-    #define SERIAL_OUT(WHAT, V...) do{ \
-      const bool port2_open = TERN1(HAS_ETHERNET, ethernet.have_telnet_client); \
-      if ( serial_port_index == 0 || serial_port_index == SERIAL_BOTH)                (void)MYSERIAL0.WHAT(V); \
-      if ((serial_port_index == 1 || serial_port_index == SERIAL_BOTH) && port2_open) (void)MYSERIAL1.WHAT(V); \
-    }while(0)
+    typedef MultiSerial<decltype(MYSERIAL0), TERN(HAS_ETHERNET, ConditionalSerial<decltype(MYSERIAL1)>, decltype(MYSERIAL1)), 0>      SerialOutputT;
   #endif
-
-  #define SERIAL_ASSERT(P)      if(serial_port_index!=(P)){ debugger(); }
+  extern SerialOutputT          multiSerial;
+  #define SERIAL_IMPL           multiSerial
 #else
   #define _PORT_REDIRECT(n,p)   NOOP
-  #define _PORT_RESTORE(n)      NOOP
-  #define SERIAL_OUT(WHAT, V...) (void)MYSERIAL0.WHAT(V)
   #define SERIAL_ASSERT(P)      NOOP
+  #define SERIAL_IMPL           MYSERIAL0
 #endif
 
+#define SERIAL_OUT(WHAT, V...)  (void)SERIAL_IMPL.WHAT(V)
+
 #define PORT_REDIRECT(p)        _PORT_REDIRECT(1,p)
-#define PORT_RESTORE()          _PORT_RESTORE(1)
+#define SERIAL_PORTMASK(P)      _BV(P)
 
 #define SERIAL_ECHO(x)          SERIAL_OUT(print, x)
 #define SERIAL_ECHO_F(V...)     SERIAL_OUT(print, V)
 #define SERIAL_ECHOLN(x)        SERIAL_OUT(println, x)
 #define SERIAL_PRINT(x,b)       SERIAL_OUT(print, x, b)
 #define SERIAL_PRINTLN(x,b)     SERIAL_OUT(println, x, b)
-#define SERIAL_PRINTF(V...)     SERIAL_OUT(printf, V)
 #define SERIAL_FLUSH()          SERIAL_OUT(flush)
 
 #ifdef ARDUINO_ARCH_STM32

Marlin/src/core/serial_base.h

+/**
+ * Marlin 3D Printer Firmware
+ * Copyright (c) 2020 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
+ *
+ * Based on Sprinter and grbl.
+ * Copyright (c) 2011 Camiel Gubbels / Erik van der Zalm
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ */
+#pragma once
+
+#include "../inc/MarlinConfigPre.h"
+
+#if ENABLED(EMERGENCY_PARSER)
+  #include "../feature/e_parser.h"
+#endif
+
+#ifndef DEC
+  #define DEC 10
+  #define HEX 16
+  #define OCT 8
+  #define BIN 2
+#endif
+
+// flushTX is not implemented in all HAL, so use SFINAE to call the method where it is.
+CALL_IF_EXISTS_IMPL(void, flushTX );
+CALL_IF_EXISTS_IMPL(bool, connected, true);
+
+// Using Curiously Recurring Template Pattern here to avoid virtual table cost when compiling.
+// Since the real serial class is known at compile time, this results in compiler writing a completely
+// efficient code
+template <class Child>
+struct SerialBase {
+  #if ENABLED(EMERGENCY_PARSER)
+    const bool ep_enabled;
+    EmergencyParser::State emergency_state;
+    inline bool emergency_parser_enabled() { return ep_enabled; }
+    SerialBase(bool ep_capable) : ep_enabled(ep_capable), emergency_state(EmergencyParser::State::EP_RESET) {}
+  #else
+    SerialBase(const bool) {}
+  #endif
+
+  // Static dispatch methods below:
+  // The most important method here is where it all ends to:
+  size_t write(uint8_t c)           { return static_cast<Child*>(this)->write(c); }
+  // Called when the parser finished processing an instruction, usually build to nothing
+  void msgDone()                    { static_cast<Child*>(this)->msgDone(); }
+  // Called upon initialization
+  void begin(const long baudRate)   { static_cast<Child*>(this)->begin(baudRate); }
+  // Called upon destruction
+  void end()                        { static_cast<Child*>(this)->end(); }
+  /** Check for available data from the port
+      @param index  The port index, usually 0 */
+  bool available(uint8_t index = 0) { return static_cast<Child*>(this)->available(index); }
+  /** Read a value from the port
+      @param index  The port index, usually 0 */
+  int  read(uint8_t index = 0)      { return static_cast<Child*>(this)->read(index); }
+  // Check if the serial port is connected (usually bypassed)
+  bool connected()                  { return static_cast<Child*>(this)->connected(); }
+  // Redirect flush
+  void flush()                      { static_cast<Child*>(this)->flush(); }
+  // Not all implementation have a flushTX, so let's call them only if the child has the implementation
+  void flushTX()                    { CALL_IF_EXISTS(void, static_cast<Child*>(this), flushTX); }
+
+  // Glue code here
+  FORCE_INLINE void write(const char* str)                    { while (*str) write(*str++); }
+  FORCE_INLINE void write(const uint8_t* buffer, size_t size) { while (size--) write(*buffer++); }
+  FORCE_INLINE void print(const char* str)                    { write(str); }
+  FORCE_INLINE void print(char c, int base = 0)               { print((long)c, base); }
+  FORCE_INLINE void print(unsigned char c, int base = 0)      { print((unsigned long)c, base); }
+  FORCE_INLINE void print(int c, int base = DEC)              { print((long)c, base); }
+  FORCE_INLINE void print(unsigned int c, int base = DEC)     { print((unsigned long)c, base); }
+  void print(long c, int base = DEC)            { if (!base) write(c); write((const uint8_t*)"-", c < 0); printNumber(c < 0 ? -c : c, base); }
+  void print(unsigned long c, int base = DEC)   { printNumber(c, base); }
+  void print(double c, int digits = 2)          { printFloat(c, digits); }
+
+  FORCE_INLINE void println(const char s[])                  { print(s); println(); }
+  FORCE_INLINE void println(char c, int base = 0)            { print(c, base); println(); }
+  FORCE_INLINE void println(unsigned char c, int base = 0)   { print(c, base); println(); }
+  FORCE_INLINE void println(int c, int base = DEC)           { print(c, base); println(); }
+  FORCE_INLINE void println(unsigned int c, int base = DEC)  { print(c, base); println(); }
+  FORCE_INLINE void println(long c, int base = DEC)          { print(c, base); println(); }
+  FORCE_INLINE void println(unsigned long c, int base = DEC) { print(c, base); println(); }
+  FORCE_INLINE void println(double c, int digits = 2)        { print(c, digits); println(); }
+  void println()                                { write("\r\n"); }
+
+  // Print a number with the given base
+  void printNumber(unsigned long n, const uint8_t base) {
+    if (n) {
+      unsigned char buf[8 * sizeof(long)]; // Enough space for base 2
+      int8_t i = 0;
+      while (n) {
+        buf[i++] = n % base;
+        n /= base;
+      }
+      while (i--) write((char)(buf[i] + (buf[i] < 10 ? '0' : 'A' - 10)));
+    }
+    else write('0');
+  }
+
+  // Print a decimal number
+  void printFloat(double number, uint8_t digits) {
+    // Handle negative numbers
+    if (number < 0.0) {
+      write('-');
+      number = -number;
+    }
+
+    // Round correctly so that print(1.999, 2) prints as "2.00"
+    double rounding = 0.5;
+    LOOP_L_N(i, digits) rounding *= 0.1;
+    number += rounding;
+
+    // Extract the integer part of the number and print it
+    unsigned long int_part = (unsigned long)number;
+    double remainder = number - (double)int_part;
+    printNumber(int_part, 10);
+
+    // Print the decimal point, but only if there are digits beyond
+    if (digits) {
+      write('.');
+      // Extract digits from the remainder one at a time
+      while (digits--) {
+        remainder *= 10.0;
+        int toPrint = int(remainder);
+        printNumber(toPrint, 10);
+        remainder -= toPrint;
+      }
+    }
+  }
+};
+
+// All serial instances will be built by chaining the features required for the function in a form of a template
+// type definition

Marlin/src/core/serial_hook.h

+/**
+ * Marlin 3D Printer Firmware
+ * Copyright (c) 2020 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
+ *
+ * Based on Sprinter and grbl.
+ * Copyright (c) 2011 Camiel Gubbels / Erik van der Zalm
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ */
+#pragma once
+
+#include "serial_base.h"
+
+// The most basic serial class: it dispatch to the base serial class with no hook whatsoever. This will compile to nothing but the base serial class
+template <class SerialT>
+struct BaseSerial : public SerialBase< BaseSerial<SerialT> >, public SerialT {
+  typedef SerialBase< BaseSerial<SerialT> > BaseClassT;
+
+  // It's required to implement a write method here to help compiler disambiguate what method to call
+  using SerialT::write;
+  using SerialT::flush;
+
+  void msgDone() {}
+
+  bool available(uint8_t index) { return index == 0 && SerialT::available(); }
+  int read(uint8_t index)       { return index == 0 ? SerialT::read() : -1; }
+  bool connected()              { return CALL_IF_EXISTS(bool, static_cast<SerialT*>(this), connected);; }
+  // We have 2 implementation of the same method in both base class, let's say which one we want
+  using SerialT::available;
+  using SerialT::read;
+  using SerialT::begin;
+  using SerialT::end;
+
+  using BaseClassT::print;
+  using BaseClassT::println;
+
+  BaseSerial(const bool e) : BaseClassT(e) {}
+
+  // Forward constructor
+  template <typename... Args>
+  BaseSerial(const bool e, Args... args) : BaseClassT(e), SerialT(args...) {}
+};
+
+// A serial with a condition checked at runtime for its output
+// A bit less efficient than static dispatching but since it's only used for ethernet's serial output right now, it's ok.
+template <class SerialT>
+struct ConditionalSerial : public SerialBase< ConditionalSerial<SerialT> > {
+  typedef SerialBase< ConditionalSerial<SerialT> > BaseClassT;
+
+  bool    & condition;
+  SerialT & out;
+  size_t write(uint8_t c) { if (condition) return out.write(c); return 0; }
+  void flush()            { if (condition) out.flush();  }
+  void begin(long br)     { out.begin(br); }
+  void end()              { out.end(); }
+
+  void msgDone() {}
+  bool connected()              { return CALL_IF_EXISTS(bool, &out, connected); }
+
+  bool available(uint8_t index) { return index == 0 && out.available(); }
+  int read(uint8_t index)       { return index == 0 ? out.read() : -1; }
+  using BaseClassT::available;
+  using BaseClassT::read;
+
+  ConditionalSerial(bool & conditionVariable, SerialT & out, const bool e) : BaseClassT(e), condition(conditionVariable), out(out) {}
+};
+
+// A simple foward class that taking a reference to an existing serial instance (likely created in their respective framework)
+template <class SerialT>
+struct ForwardSerial : public SerialBase< ForwardSerial<SerialT> > {
+  typedef SerialBase< ForwardSerial<SerialT> > BaseClassT;
+
+  SerialT & out;
+  size_t write(uint8_t c) { return out.write(c); }
+  void flush()            { out.flush();  }
+  void begin(long br)     { out.begin(br); }
+  void end()              { out.end(); }
+
+  void msgDone() {}
+  // Existing instances implement Arduino's operator bool, so use that if it's available
+  bool connected()              { return Private::HasMember_connected<SerialT>::value ? CALL_IF_EXISTS(bool, &out, connected) : (bool)out; }
+
+  bool available(uint8_t index) { return index == 0 && out.available(); }
+  int read(uint8_t index)       { return index == 0 ? out.read() : -1; }
+  bool available()              { return out.available(); }
+  int read()                    { return out.read(); }
+
+  ForwardSerial(const bool e, SerialT & out) : BaseClassT(e), out(out) {}
+};
+
+// A class that's can be hooked and unhooked at runtime, useful to capturing the output of the serial interface
+template <class SerialT>
+struct RuntimeSerial : public SerialBase< RuntimeSerial<SerialT> >, public SerialT {
+  typedef SerialBase< RuntimeSerial<SerialT> > BaseClassT;
+  typedef void (*WriteHook)(void * userPointer, uint8_t c);
+  typedef void (*EndOfMessageHook)(void * userPointer);
+
+  WriteHook        writeHook;
+  EndOfMessageHook eofHook;
+  void *           userPointer;
+
+  size_t write(uint8_t c) {
+    if (writeHook) writeHook(userPointer, c);
+    return SerialT::write(c);
+  }
+
+  void msgDone() {
+    if (eofHook) eofHook(userPointer);
+  }
+
+  bool available(uint8_t index) { return index == 0 && SerialT::available(); }
+  int read(uint8_t index)       { return index == 0 ? SerialT::read() : -1; }
+  using SerialT::available;
+  using SerialT::read;
+  using SerialT::flush;
+  using SerialT::begin;
+  using SerialT::end;
+
+  using BaseClassT::print;
+  using BaseClassT::println;
+  
+
+  void setHook(WriteHook writeHook = 0, EndOfMessageHook eofHook = 0, void * userPointer = 0) {
+    // Order is important here as serial code can be called inside interrupts
+    // When setting a hook, the user pointer must be set first so if writeHook is called as soon as it's set, it'll be valid
+    if (userPointer) this->userPointer = userPointer;
+    this->writeHook = writeHook;
+    this->eofHook = eofHook;
+    // Order is important here because of asynchronous access here
+    // When unsetting a hook, the user pointer must be unset last so that any pending writeHook is still using the old pointer
+    if (!userPointer) this->userPointer = 0;
+  }
+
+  RuntimeSerial(const bool e) : BaseClassT(e), writeHook(0), eofHook(0), userPointer(0) {}
+
+  // Forward constructor
+  template <typename... Args>
+  RuntimeSerial(const bool e, Args... args) : BaseClassT(e), SerialT(args...) {}
+};
+
+// A class that's duplicating its output conditionally to 2 serial interface
+template <class Serial0T, class Serial1T, const uint8_t offset = 0>
+struct MultiSerial : public SerialBase< MultiSerial<Serial0T, Serial1T, offset> > {
+  typedef SerialBase< MultiSerial<Serial0T, Serial1T, offset> > BaseClassT;
+
+  uint8_t    portMask;
+  Serial0T & serial0;
+  Serial1T & serial1;
+
+  enum Masks {
+    FirstOutputMask   =  (1 << offset),
+    SecondOutputMask  =  (1 << (offset + 1)),
+    AllMask           = FirstOutputMask | SecondOutputMask,
+  };
+
+  size_t write(uint8_t c) {
+    size_t ret = 0;
+    if (portMask & FirstOutputMask)   ret = serial0.write(c);
+    if (portMask & SecondOutputMask)  ret = serial1.write(c) | ret;
+    return ret;
+  }
+  void msgDone() {
+    if (portMask & FirstOutputMask)   serial0.msgDone();
+    if (portMask & SecondOutputMask)  serial1.msgDone();
+  }
+  bool available(uint8_t index) {
+    switch(index) {
+      case 0 + offset: return serial0.available();
+      case 1 + offset: return serial1.available();
+      default: return false;
+    }
+  }
+  int read(uint8_t index) {
+    switch(index) {
+      case 0 + offset: return serial0.read();
+      case 1 + offset: return serial1.read();
+      default: return -1;
+    }
+  }
+  void begin(const long br) {
+    if (portMask & FirstOutputMask)   serial0.begin(br);
+    if (portMask & SecondOutputMask)  serial1.begin(br);
+  }
+  void end() {
+    if (portMask & FirstOutputMask)   serial0.end();
+    if (portMask & SecondOutputMask)  serial1.end();
+  }
+  bool connected() {
+    bool ret = true;
+    if (portMask & FirstOutputMask)   ret = CALL_IF_EXISTS(bool, &serial0, connected);
+    if (portMask & SecondOutputMask)  ret = ret && CALL_IF_EXISTS(bool, &serial1, connected);
+    return ret;
+  }
+
+  using BaseClassT::available;
+  using BaseClassT::read;
+
+  // Redirect flush
+  void flush()      {
+    if (portMask & FirstOutputMask)   serial0.flush();
+    if (portMask & SecondOutputMask)  serial1.flush();
+  }
+  void flushTX()    {
+    if (portMask & FirstOutputMask)   CALL_IF_EXISTS(void, &serial0, flushTX);
+    if (portMask & SecondOutputMask)  CALL_IF_EXISTS(void, &serial1, flushTX);
+  }
+
+  MultiSerial(Serial0T & serial0, Serial1T & serial1, int8_t mask = AllMask, const bool e = false) :
+    BaseClassT(e),
+    portMask(mask), serial0(serial0), serial1(serial1) {}
+};
+
+// Build the actual serial object depending on current configuration
+#define Serial0Type TERN(SERIAL_RUNTIME_HOOK, RuntimeSerial, BaseSerial)
+#define ForwardSerial0Type TERN(SERIAL_RUNTIME_HOOK, RuntimeSerial, ForwardSerial)
+#ifdef HAS_MULTI_SERIAL
+  #define Serial1Type ConditionalSerial
+#endif

Marlin/src/feature/binary_stream.h

 #endif
 
 inline bool bs_serial_data_available(const uint8_t index) {
-  switch (index) {
-    case 0: return MYSERIAL0.available();
-    #if HAS_MULTI_SERIAL
-      case 1: return MYSERIAL1.available();
-    #endif
-  }
-  return false;
+  return SERIAL_IMPL.available(index);
 }
 
 inline int bs_read_serial(const uint8_t index) {
-  switch (index) {
-    case 0: return MYSERIAL0.read();
-    #if HAS_MULTI_SERIAL
-      case 1: return MYSERIAL1.read();
-    #endif
-  }
-  return -1;
+  return SERIAL_IMPL.read(index);
 }
 
 #if ENABLED(BINARY_STREAM_COMPRESSION)
     millis_t transfer_window = millis() + RX_TIMESLICE;
 
     #if ENABLED(SDSUPPORT)
-      PORT_REDIRECT(card.transfer_port_index);
+      PORT_REDIRECT(SERIAL_PORTMASK(card.transfer_port_index));
     #endif
 
     #pragma GCC diagnostic push

Marlin/src/feature/host_actions.cpp

 #endif
 
 void host_action(PGM_P const pstr, const bool eol) {
-  PORT_REDIRECT(SERIAL_BOTH);
+  PORT_REDIRECT(SERIAL_ALL);
   SERIAL_ECHOPGM("//action:");
   serialprintPGM(pstr);
   if (eol) SERIAL_EOL();
   PromptReason host_prompt_reason = PROMPT_NOT_DEFINED;
 
   void host_action_notify(const char * const message) {
-    PORT_REDIRECT(SERIAL_BOTH);
+    PORT_REDIRECT(SERIAL_ALL);
     host_action(PSTR("notification "), false);
     SERIAL_ECHOLN(message);
   }
 
   void host_action_notify_P(PGM_P const message) {
-    PORT_REDIRECT(SERIAL_BOTH);
+    PORT_REDIRECT(SERIAL_ALL);
     host_action(PSTR("notification "), false);
     serialprintPGM(message);
     SERIAL_EOL();
   }
 
   void host_action_prompt(PGM_P const ptype, const bool eol=true) {
-    PORT_REDIRECT(SERIAL_BOTH);
+    PORT_REDIRECT(SERIAL_ALL);
     host_action(PSTR("prompt_"), false);
     serialprintPGM(ptype);
     if (eol) SERIAL_EOL();
 
   void host_action_prompt_plus(PGM_P const ptype, PGM_P const pstr, const char extra_char='\0') {
     host_action_prompt(ptype, false);
-    PORT_REDIRECT(SERIAL_BOTH);
+    PORT_REDIRECT(SERIAL_ALL);
     SERIAL_CHAR(' ');
     serialprintPGM(pstr);
     if (extra_char != '\0') SERIAL_CHAR(extra_char);

Marlin/src/gcode/feature/network/M552-M554.cpp

     Ethernet.MACAddress(mac);
     SERIAL_ECHOPGM("  MAC: ");
     LOOP_L_N(i, 6) {
-      SERIAL_PRINTF("%02X", mac[i]);
+      if (mac[i] < 16) SERIAL_CHAR('0');
+      SERIAL_PRINT(mac[i], HEX);
       if (i < 5) SERIAL_CHAR(':');
     }
   }

Marlin/src/gcode/gcode.cpp

   }
 
   if (!no_ok) queue.ok_to_send();
+
+  SERIAL_OUT(msgDone); // Call the msgDone serial hook to signal command processing done
 }
 
 /**
 void GcodeSuite::process_next_command() {
   char * const current_command = queue.command_buffer[queue.index_r];
 
-  PORT_REDIRECT(queue.port[queue.index_r]);
+  PORT_REDIRECT(SERIAL_PORTMASK(queue.port[queue.index_r]));
 
   #if ENABLED(POWER_LOSS_RECOVERY)
     recovery.queue_index_r = queue.index_r;

Marlin/src/gcode/host/M118.cpp

   }
 
   #if HAS_MULTI_SERIAL
-    const serial_index_t old_serial = serial_port_index;
+    const int8_t old_serial = multiSerial.portMask;
     if (WITHIN(port, 0, NUM_SERIAL))
-      serial_port_index = (
-        port == 0 ? SERIAL_BOTH
-        : port == 1 ? 0
-        #if HAS_MULTI_SERIAL
-          : port == 2 ? 1
-        #endif
-        : SERIAL_PORT
-      );
+      multiSerial.portMask = port ? _BV(port - 1) : SERIAL_ALL;
   #endif
 
   if (hasE) SERIAL_ECHO_START();
   if (hasA) SERIAL_ECHOPGM("//");
   SERIAL_ECHOLN(p);
 
-  TERN_(HAS_MULTI_SERIAL, serial_port_index = old_serial);
+  TERN_(HAS_MULTI_SERIAL, multiSerial.portMask = old_serial);
 }

Marlin/src/gcode/queue.cpp

 void GCodeQueue::ok_to_send() {
   #if HAS_MULTI_SERIAL
     const serial_index_t serial_ind = command_port();
-    if (serial_ind < 0) return;                   // Never mind. Command came from SD or Flash Drive
-    PORT_REDIRECT(serial_ind);                    // Reply to the serial port that sent the command
+    if (serial_ind < 0) return;
+    PORT_REDIRECT(SERIAL_PORTMASK(serial_ind));   // Reply to the serial port that sent the command
   #endif
   if (!send_ok[index_r]) return;
   SERIAL_ECHOPGM(STR_OK);
   const serial_index_t serial_ind = command_port();
   #if HAS_MULTI_SERIAL
     if (serial_ind < 0) return;                   // Never mind. Command came from SD or Flash Drive
-    PORT_REDIRECT(serial_ind);                    // Reply to the serial port that sent the command
+    PORT_REDIRECT(SERIAL_PORTMASK(serial_ind));   // Reply to the serial port that sent the command
   #endif
   SERIAL_FLUSH();
   SERIAL_ECHOPGM(STR_RESEND);
 }
 
 void GCodeQueue::gcode_line_error(PGM_P const err, const serial_index_t serial_ind) {
-  PORT_REDIRECT(serial_ind);                      // Reply to the serial port that sent the command
+  PORT_REDIRECT(SERIAL_PORTMASK(serial_ind)); // Reply to the serial port that sent the command
   SERIAL_ERROR_START();
   serialprintPGM(err);
   SERIAL_ECHOLN(last_N[serial_ind]);
-  while (read_serial(serial_ind) != -1);          // Clear out the RX buffer
+  while (read_serial(serial_ind) != -1);      // Clear out the RX buffer
   flush_and_request_resend();
   serial_count[serial_ind] = 0;
 }
                 #if ENABLED(BEZIER_CURVE_SUPPORT)
                   case 5:
                 #endif
-                  PORT_REDIRECT(p);                      // Reply to the serial port that sent the command
+                  PORT_REDIRECT(SERIAL_PORTMASK(p));     // Reply to the serial port that sent the command
                   SERIAL_ECHOLNPGM(STR_ERR_STOPPED);
                   LCD_MESSAGEPGM(MSG_STOPPED);
                   break;

Marlin/src/gcode/sd/M1001.cpp

 
   // Announce SD file completion
   {
-    PORT_REDIRECT(SERIAL_BOTH);
+    PORT_REDIRECT(SERIAL_ALL);
     SERIAL_ECHOLNPGM(STR_FILE_PRINTED);
   }
 

Marlin/src/inc/Conditionals_LCD.h

 // FSMC/SPI TFT Panels (LVGL)
 #if ENABLED(TFT_LVGL_UI)
   #define HAS_TFT_LVGL_UI 1
+  #define SERIAL_RUNTIME_HOOK 1
 #endif
 
 // FSMC/SPI TFT Panels

Marlin/src/lcd/extui/malyan_lcd.cpp

   // This is mildly different than stock, which
   // appears to use the usb discovery status.
   // This is more logical.
-  if (last_usb_connected_status != MYSERIAL0 || forceUpdate) {
-    last_usb_connected_status = MYSERIAL0;
+  if (last_usb_connected_status != MYSERIAL0.connected() || forceUpdate) {
+    last_usb_connected_status = MYSERIAL0.connected();
     write_to_lcd_P(last_usb_connected_status ? PSTR("{R:UC}\r\n") : PSTR("{R:UD}\r\n"));
   }
 }

Marlin/src/module/temperature.cpp

      */
     void Temperature::report_fan_speed(const uint8_t target) {
       if (target >= FAN_COUNT) return;
-      PORT_REDIRECT(SERIAL_BOTH);
+      PORT_REDIRECT(SERIAL_ALL);
       SERIAL_ECHOLNPAIR("M106 P", target, " S", fan_speed[target]);
     }
   #endif
     void Temperature::auto_report_temperatures() {
       if (auto_report_temp_interval && ELAPSED(millis(), next_temp_report_ms)) {
         next_temp_report_ms = millis() + 1000UL * auto_report_temp_interval;
-        PORT_REDIRECT(SERIAL_BOTH);
+        PORT_REDIRECT(SERIAL_ALL);
         print_heater_states(active_extruder);
         SERIAL_EOL();
       }

Marlin/src/sd/cardreader.cpp

 
 void announceOpen(const uint8_t doing, const char * const path) {
   if (doing) {
-    PORT_REDIRECT(SERIAL_BOTH);
+    PORT_REDIRECT(SERIAL_ALL);
     SERIAL_ECHO_START();
     SERIAL_ECHOPGM("Now ");
     serialprintPGM(doing == 1 ? PSTR("doing") : PSTR("fresh"));
     SERIAL_ECHOLNPAIR(" file: ", path);
-    PORT_RESTORE();
   }
 }
 
     filesize = file.fileSize();
     sdpos = 0;
 
-    PORT_REDIRECT(SERIAL_BOTH);
-    SERIAL_ECHOLNPAIR(STR_SD_FILE_OPENED, fname, STR_SD_SIZE, filesize);
-    SERIAL_ECHOLNPGM(STR_SD_FILE_SELECTED);
-    PORT_RESTORE();
+    { // Don't remove this block, as the PORT_REDIRECT is a RAII
+      PORT_REDIRECT(SERIAL_ALL);
+      SERIAL_ECHOLNPAIR(STR_SD_FILE_OPENED, fname, STR_SD_SIZE, filesize);
+      SERIAL_ECHOLNPGM(STR_SD_FILE_SELECTED);
+    }
 
     selectFileByName(fname);
     ui.set_status(longFilename[0] ? longFilename : fname);

Marlin/src/sd/cardreader.h

   #if ENABLED(AUTO_REPORT_SD_STATUS)
     static void auto_report_sd_status();
     static inline void set_auto_report_interval(uint8_t v) {
-      TERN_(HAS_MULTI_SERIAL, auto_report_port = serial_port_index);
+      TERN_(HAS_MULTI_SERIAL, auto_report_port = serialHook.portMask);
       NOMORE(v, 60);
       auto_report_sd_interval = v;
       next_sd_report_ms = millis() + 1000UL * v;

buildroot/tests/run_tests

   if [[ -z "$VERBOSE_PLATFORMIO" ]] ; then
     silent="--silent"
   else
-    silent=""
+    silent="-v"
   fi
   if platformio run --project-dir $1 -e $2 $silent; then
     printf "\033[0;32mPassed\033[0m\n"

docs/Serial.md

+# Serial port architecture in Marlin
+
+Marlin is targeting a pletora of different CPU architecture and platforms. Each of these platforms has its own serial interface.
+While many provide a Arduino-like Serial class, it's not all of them, and the differences in the existing API create a very complex brain teaser for writing code that works more or less on each platform.
+
+Moreover, many platform have intrinsic needs about serial port (like forwarding the output on multiple serial port, providing a *serial-like* telnet server, mixing USB-based serial port with SD card emulation) that are difficult to handle cleanly in the other platform serial logic.
+
+
+Starting with version `2.0.9`, Marlin provides a common interface for its serial needs.
+
+## Common interface
+
+This interface is declared in `Marlin/src/core/serial_base.h` 
+Any implementation will need to follow this interface for being used transparently in Marlin's codebase.
+
+The implementation was written to prioritize performance over abstraction, so the base interface is not using virtual inheritance to avoid the cost of virtual dispatching while calling methods.
+Instead, the Curiously Recurring Template Pattern (**CRTP**) is used so that, upon compilation, the interface abstraction does not incur a performance cost.
+
+Because some platform do not follow the same interface, the missing method in the actual low-level implementation are detected via SFINAE and a wrapper is generated when such method are missing. See `CALL_IF_EXISTS` macro in `Marlin/src/core/macros.h` for the documentation of this technic.  
+
+## Composing the desired feature
+The different specificities for each architecture are provided by composing the serial type based on desired functionality.
+In the `Marlin/src/core/serial_hook.h` file, the different serial feature are declared and defined in each templated type:
+1. `BaseSerial` is a simple 1:1 wrapper to the underlying, Arduino compatible, `Serial`'s class. It derives from it. You'll use this if the platform does not do anything specific for the `Serial` object (for example, if an interrupt callback calls directly the serial **instance** in the platform's framework code, this is not the right class to use). This wrapper is completely inlined so that it does not generate any code upon compilation. `BaseSerial` constructor forwards any parameter to the platform's `Serial`'s constructor.
+2. `ForwardSerial` is a composing wrapper. It references an actual Arduino compatible `Serial` instance. You'll use this if the instance is declared in the platform's framework and is being referred directly in the framework. This is not as efficient as the `BaseSerial` implementation since static dereferencing is done for each method call (it'll still be faster than virtual dispatching)
+3. `ConditionalSerial` is working a bit like the `ForwardSerial` interface, but it checks a boolean condition before calling the referenced instance. You'll use it when the serial output can be switch off at runtime, for example in a *telnet* like serial output that should not emit any packet if no client is connected.
+4. `RuntimeSerial` is providing a runtime-modifiable hooking method for its `write` and `msgDone` method. You'll use it if you need to capture the serial output of Marlin, for example to display the G-Code parser's output on a GUI interface. The hooking interface is setup via the `setHook` method.
+5. `MultiSerial` is a runtime modifiable serial output multiplexer. It can output (*respectively input*) to 2 different interface based on a port *mask*. You'll use this if you need to output the same serial stream to multiple port. You can plug a `MultiSerial` to itself to duplicate to more than 2 ports. 
+
+## Plumbing
+Since all the types above are using CRTP, it's possible to combine them to get the appropriate functionality. 
+This is easily done via type definition of the feature. 
+
+For example, to present a serial interface that's outputting to 2 serial port, the first one being hooked at runtime and the second one connected to a runtime switchable telnet client, you'll declare the type to use as:
+```
+typedef MultiSerial< RuntimeSerial<Serial>, ConditionalSerial<TelnetClient> > Serial0Type;
+```
+
+## Emergency parser
+By default, the serial base interface provide an emergency parser that's only enable for serial classes that support it. 
+Because of this condition, all underlying type takes a first `bool emergencyParserEnabled` argument to their constructor. You must take into account this parameter when defining the actual type used. 
+
+
+*This document was written by [X-Ryl669](https://blog.cyril.by) and is under [CC-SA license](https://creativecommons.org/licenses/by-sa)*