Support a third serial port (#21784)

Marlin/src/HAL/AVR/HAL.h

@@ -103,6 +103,13 @@ typedef int8_t pin_t;
     #endif
     #define MYSERIAL2 customizedSerial2
   #endif
+
+  #ifdef SERIAL_PORT_3
+    #if !WITHIN(SERIAL_PORT_3, -1, 3)
+      #error "SERIAL_PORT_3 must be from 0 to 3, or -1 for USB Serial."
+    #endif
+    #define MYSERIAL3 customizedSerial3
+  #endif
 #endif
 
 #ifdef MMU2_SERIAL_PORT

Marlin/src/HAL/AVR/MarlinSerial.cpp

@@ -585,6 +585,22 @@ MSerialT1 customizedSerial1(MSerialT1::HasEmergencyParser);
 
 #endif // SERIAL_PORT_2
 
+#ifdef SERIAL_PORT_3
+
+  // Hookup ISR handlers
+  ISR(SERIAL_REGNAME(USART, SERIAL_PORT_3, _RX_vect)) {
+    MarlinSerial<MarlinSerialCfg<SERIAL_PORT_3>>::store_rxd_char();
+  }
+
+  ISR(SERIAL_REGNAME(USART, SERIAL_PORT_3, _UDRE_vect)) {
+    MarlinSerial<MarlinSerialCfg<SERIAL_PORT_3>>::_tx_udr_empty_irq();
+  }
+
+  template class MarlinSerial< MarlinSerialCfg<SERIAL_PORT_3> >;
+  MSerialT3 customizedSerial3(MSerialT3::HasEmergencyParser);
+
+#endif // SERIAL_PORT_3
+
 #ifdef MMU2_SERIAL_PORT
 
   ISR(SERIAL_REGNAME(USART, MMU2_SERIAL_PORT, _RX_vect)) {

Marlin/src/HAL/AVR/MarlinSerial.h

@@ -246,6 +246,11 @@
     extern MSerialT2 customizedSerial2;
   #endif
 
+  #ifdef SERIAL_PORT_3
+    typedef Serial1Class< MarlinSerial< MarlinSerialCfg<SERIAL_PORT_3> > > MSerialT3;
+    extern MSerialT3 customizedSerial3;
+  #endif
+
 #endif // !USBCON
 
 #ifdef MMU2_SERIAL_PORT

Marlin/src/HAL/DUE/HAL.h

@@ -68,6 +68,16 @@ extern DefaultSerial4 MSerial3;
   #endif
 #endif
 
+#ifdef SERIAL_PORT_3
+  #if SERIAL_PORT_3 == -1 || ENABLED(EMERGENCY_PARSER)
+    #define MYSERIAL3 customizedSerial3
+  #elif WITHIN(SERIAL_PORT_3, 0, 3)
+    #define MYSERIAL3 MSERIAL(SERIAL_PORT_3)
+  #else
+    #error "SERIAL_PORT_3 must be from 0 to 3, or -1 for USB Serial."
+  #endif
+#endif
+
 #ifdef MMU2_SERIAL_PORT
   #if WITHIN(MMU2_SERIAL_PORT, 0, 3)
     #define MMU2_SERIAL MSERIAL(MMU2_SERIAL_PORT)

Marlin/src/HAL/DUE/MarlinSerial.cpp

@@ -486,4 +486,9 @@ void MarlinSerial<Cfg>::flushTX() {
   MSerialT2 customizedSerial2(MarlinSerialCfg<SERIAL_PORT_2>::EMERGENCYPARSER);
 #endif
 
+#if defined(SERIAL_PORT_3) && SERIAL_PORT_3 >= 0
+  template class MarlinSerial< MarlinSerialCfg<SERIAL_PORT_3> >;
+  MSerialT3 customizedSerial3(MarlinSerialCfg<SERIAL_PORT_3>::EMERGENCYPARSER);
+#endif
+
 #endif // ARDUINO_ARCH_SAM

Marlin/src/HAL/DUE/MarlinSerial.h

@@ -149,3 +149,8 @@ struct MarlinSerialCfg {
   typedef Serial1Class< MarlinSerial< MarlinSerialCfg<SERIAL_PORT_2> > > MSerialT2;
   extern MSerialT2 customizedSerial2;
 #endif
+
+#if defined(SERIAL_PORT_3) && SERIAL_PORT_3 >= 0
+  typedef Serial1Class< MarlinSerial< MarlinSerialCfg<SERIAL_PORT_3> > > MSerialT3;
+  extern MSerialT3 customizedSerial3;
+#endif

Marlin/src/HAL/DUE/MarlinSerialUSB.cpp

@@ -134,6 +134,9 @@ size_t MarlinSerialUSB::write(const uint8_t c) {
 #if SERIAL_PORT_2 == -1
   MSerialT2 customizedSerial2(TERN0(EMERGENCY_PARSER, true));
 #endif
+#if SERIAL_PORT_3 == -1
+  MSerialT3 customizedSerial3(TERN0(EMERGENCY_PARSER, true));
+#endif
 
 #endif // HAS_USB_SERIAL
 #endif // ARDUINO_ARCH_SAM

Marlin/src/HAL/DUE/MarlinSerialUSB.h

@@ -59,3 +59,7 @@ struct MarlinSerialUSB {
   extern MSerialT2 customizedSerial2;
 #endif
 
+#if SERIAL_PORT_3 == -1
+  typedef Serial1Class<MarlinSerialUSB> MSerialT3;
+  extern MSerialT3 customizedSerial3;
+#endif

Marlin/src/HAL/LPC1768/HAL.h

@@ -84,6 +84,16 @@ extern DefaultSerial1 USBSerial;
   #endif
 #endif
 
+#ifdef SERIAL_PORT_3
+  #if SERIAL_PORT_3 == -1
+    #define MYSERIAL3 USBSerial
+  #elif WITHIN(SERIAL_PORT_3, 0, 3)
+    #define MYSERIAL3 MSERIAL(SERIAL_PORT_3)
+  #else
+    #error "SERIAL_PORT_3 must be from 0 to 3. You can also use -1 if the board supports Native USB."
+  #endif
+#endif
+
 #ifdef MMU2_SERIAL_PORT
   #if MMU2_SERIAL_PORT == -1
     #define MMU2_SERIAL USBSerial

Marlin/src/HAL/STM32/HAL.h

@@ -68,6 +68,16 @@
   #endif
 #endif
 
+#ifdef SERIAL_PORT_3
+  #if SERIAL_PORT_3 == -1
+    #define MYSERIAL3 MSerial0
+  #elif WITHIN(SERIAL_PORT_3, 1, 6)
+    #define MYSERIAL3 MSERIAL(SERIAL_PORT_3)
+  #else
+    #error "SERIAL_PORT_3 must be from 1 to 6. You can also use -1 if the board supports Native USB."
+  #endif
+#endif
+
 #ifdef MMU2_SERIAL_PORT
   #if MMU2_SERIAL_PORT == -1
     #define MMU2_SERIAL MSerial0

Marlin/src/HAL/STM32F1/HAL.h

@@ -98,6 +98,17 @@
   #endif
 #endif
 
+#ifdef SERIAL_PORT_3
+  #if SERIAL_PORT_3 == -1
+    #define MYSERIAL3 UsbSerial
+  #elif WITHIN(SERIAL_PORT_3, 1, NUM_UARTS)
+    #define MYSERIAL3 MSERIAL(SERIAL_PORT_3)
+  #else
+    #define MYSERIAL3 MSERIAL(1) // dummy port
+    static_assert(false, "SERIAL_PORT_3 must be from 1 to " STRINGIFY(NUM_UARTS) ". You can also use -1 if the board supports Native USB.")
+  #endif
+#endif
+
 #ifdef MMU2_SERIAL_PORT
   #if MMU2_SERIAL_PORT == -1
     #define MMU2_SERIAL UsbSerial