Arduino Due XON/XOFF implementation

Alos includes emergency parser and configurable TX/RX buffers for Arduino Due.

Marlin/src/HAL/HAL_DUE/HAL_Due.h

@@ -29,37 +29,35 @@
 #ifndef _HAL_DUE_H
 #define _HAL_DUE_H
 
-// --------------------------------------------------------------------------
-// Includes
-// --------------------------------------------------------------------------
-
 #include <stdint.h>
 
 #include "Arduino.h"
 
 #include "fastio_Due.h"
 #include "watchdog_Due.h"
-
 #include "HAL_timers_Due.h"
 
-// --------------------------------------------------------------------------
+//
 // Defines
-// --------------------------------------------------------------------------
+//
 
 #if SERIAL_PORT == -1
   #define MYSERIAL SerialUSB
 #elif SERIAL_PORT == 0
-  #define MYSERIAL Serial
+  #define MYSERIAL customizedSerial
 #elif SERIAL_PORT == 1
-  #define MYSERIAL Serial1
+  #define MYSERIAL customizedSerial
 #elif SERIAL_PORT == 2
-  #define MYSERIAL Serial2
+  #define MYSERIAL customizedSerial
 #elif SERIAL_PORT == 3
-  #define MYSERIAL Serial3
+  #define MYSERIAL customizedSerial
 #endif
 
 #define _BV(bit) (1 << (bit))
 
+// We need the previous define before the include, or compilation bombs...
+#include "MarlinSerial_Due.h"
+
 #ifndef analogInputToDigitalPin
   #define analogInputToDigitalPin(p) ((p < 12u) ? (p) + 54u : -1)
 #endif
@@ -102,46 +100,43 @@ typedef int8_t pin_t;
 // Public Variables
 // --------------------------------------------------------------------------
 
-/** result of last ADC conversion */
-extern uint16_t HAL_adc_result;
+extern uint16_t HAL_adc_result;     // result of last ADC conversion
 
-// --------------------------------------------------------------------------
-// Public functions
-// --------------------------------------------------------------------------
-
-// Disable interrupts
-void cli(void);
-
-// Enable interrupts
-void sei(void);
-
-/** clear reset reason */
-void HAL_clear_reset_source (void);
+void cli(void);                     // Disable interrupts
+void sei(void);                     // Enable interrupts
 
-/** reset reason */
-uint8_t HAL_get_reset_source (void);
+void HAL_clear_reset_source(void);  // clear reset reason
+uint8_t HAL_get_reset_source(void); // get reset reason
 
 void _delay_ms(const int delay);
 
 int freeMemory(void);
 
-// SPI: Extended functions which take a channel number (hardware SPI only)
-/** Write single byte to specified SPI channel */
+/**
+ * SPI: Extended functions taking a channel number (hardware SPI only)
+ */
+
+// Write single byte to specified SPI channel
 void spiSend(uint32_t chan, byte b);
-/** Write buffer to specified SPI channel */
+
+// Write buffer to specified SPI channel
 void spiSend(uint32_t chan, const uint8_t* buf, size_t n);
-/** Read single byte from specified SPI channel */
+
+// Read single byte from specified SPI channel
 uint8_t spiRec(uint32_t chan);
 
+/**
+ * EEPROM
+ */
 
-// EEPROM
 void eeprom_write_byte(unsigned char *pos, unsigned char value);
 unsigned char eeprom_read_byte(unsigned char *pos);
 void eeprom_read_block (void *__dst, const void *__src, size_t __n);
 void eeprom_update_block (const void *__src, void *__dst, size_t __n);
 
-
-// ADC
+/**
+ * ADC
+ */
 
 #define HAL_ANALOG_SELECT(pin)
 
@@ -150,20 +145,13 @@ inline void HAL_adc_init(void) {}//todo
 #define HAL_START_ADC(pin)  HAL_adc_start_conversion(pin)
 #define HAL_READ_ADC        HAL_adc_result
 
-
 void HAL_adc_start_conversion(const uint8_t adc_pin);
-
 uint16_t HAL_adc_get_result(void);
-
-//
 uint16_t HAL_getAdcReading(uint8_t chan);
-
 void HAL_startAdcConversion(uint8_t chan);
 uint8_t HAL_pinToAdcChannel(int pin);
-
 uint16_t HAL_getAdcFreerun(uint8_t chan, bool wait_for_conversion = false);
 //uint16_t HAL_getAdcSuperSample(uint8_t chan);
-
 void HAL_enable_AdcFreerun(void);
 //void HAL_disable_AdcFreerun(uint8_t chan);
 
@@ -171,9 +159,4 @@ void HAL_enable_AdcFreerun(void);
 #define GET_PIN_MAP_INDEX(pin) pin
 #define PARSED_PIN_INDEX(code, dval) parser.intval(code, dval)
 
-// --------------------------------------------------------------------------
-//
-// --------------------------------------------------------------------------
-
 #endif // _HAL_DUE_H
-

Marlin/src/HAL/HAL_DUE/MarlinSerial_Due.cpp

@@ -0,0 +1,680 @@
+/**
+ * Marlin 3D Printer Firmware
+ * Copyright (C) 2016 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 <http://www.gnu.org/licenses/>.
+ *
+ */
+
+/**
+ * MarlinSerial_Due.cpp - Hardware serial library for Arduino DUE
+ * Copyright (c) 2017 Eduardo José Tagle. All right reserved
+ * Based on MarlinSerial for AVR, copyright (c) 2006 Nicholas Zambetti.  All right reserved.
+ */
+#ifdef ARDUINO_ARCH_SAM
+
+#include "../../inc/MarlinConfig.h"
+
+#include "MarlinSerial_Due.h"
+#include "InterruptVectors_Due.h"
+#include "../../Marlin.h"
+
+// Based on selected port, use the proper configuration
+#if SERIAL_PORT == 0
+  #define HWUART UART
+  #define HWUART_IRQ UART_IRQn
+  #define HWUART_IRQ_ID ID_UART
+#elif SERIAL_PORT == 1
+  #define HWUART USART0
+  #define HWUART_IRQ USART0_IRQn
+  #define HWUART_IRQ_ID ID_USART0
+#elif SERIAL_PORT == 2
+  #define HWUART USART1
+  #define HWUART_IRQ USART1_IRQn
+  #define HWUART_IRQ_ID ID_USART1
+#elif SERIAL_PORT == 3
+  #define HWUART USART3
+  #define HWUART_IRQ USART3_IRQn
+  #define HWUART_IRQ_ID ID_USART3
+#endif
+
+struct ring_buffer_r {
+  unsigned char buffer[RX_BUFFER_SIZE];
+  volatile ring_buffer_pos_t head, tail;
+};
+
+#if TX_BUFFER_SIZE > 0
+  struct ring_buffer_t {
+    unsigned char buffer[TX_BUFFER_SIZE];
+    volatile uint8_t head, tail;
+  };
+#endif
+
+ring_buffer_r rx_buffer = { { 0 }, 0, 0 };
+#if TX_BUFFER_SIZE > 0
+  ring_buffer_t tx_buffer = { { 0 }, 0, 0 };
+  static bool _written;
+#endif
+
+#if ENABLED(SERIAL_XON_XOFF)
+  constexpr uint8_t XON_XOFF_CHAR_SENT = 0x80;  // XON / XOFF Character was sent
+  constexpr uint8_t XON_XOFF_CHAR_MASK = 0x1F;  // XON / XOFF character to send
+  // XON / XOFF character definitions
+  constexpr uint8_t XON_CHAR  = 17;
+  constexpr uint8_t XOFF_CHAR = 19;
+  uint8_t xon_xoff_state = XON_XOFF_CHAR_SENT | XON_CHAR;
+
+  // Validate that RX buffer size is at least 4096 bytes- According to several experiments, on
+  // the original Arduino Due that uses a ATmega16U2 as USB to serial bridge, due to the introduced
+  // latencies, at least 2959 bytes of RX buffering (when transmitting at 250kbits/s) are required
+  // to avoid overflows.
+
+  #if RX_BUFFER_SIZE < 4096
+    #error Arduino DUE requires at least 4096 bytes of RX buffer to avoid buffer overflows when using XON/XOFF handshake
+  #endif
+#endif
+
+#if ENABLED(SERIAL_STATS_DROPPED_RX)
+  uint8_t rx_dropped_bytes = 0;
+#endif
+
+#if ENABLED(SERIAL_STATS_MAX_RX_QUEUED)
+  ring_buffer_pos_t rx_max_enqueued = 0;
+#endif
+
+// A SW memory barrier, to ensure GCC does not overoptimize loops
+#define sw_barrier() asm volatile("": : :"memory");
+
+#if ENABLED(EMERGENCY_PARSER)
+
+  #include "../../module/stepper.h"
+
+  // Currently looking for: M108, M112, M410
+  // If you alter the parser please don't forget to update the capabilities in Conditionals_post.h
+
+  FORCE_INLINE void emergency_parser(const uint8_t c) {
+
+    static e_parser_state state = state_RESET;
+
+    switch (state) {
+    case state_RESET:
+      switch (c) {
+        case ' ': break;
+        case 'N': state = state_N;      break;
+        case 'M': state = state_M;      break;
+        default: state = state_IGNORE;
+      }
+      break;
+
+    case state_N:
+      switch (c) {
+        case '0': case '1': case '2':
+        case '3': case '4': case '5':
+        case '6': case '7': case '8':
+        case '9': case '-': case ' ':   break;
+        case 'M': state = state_M;      break;
+        default:  state = state_IGNORE;
+      }
+      break;
+
+    case state_M:
+      switch (c) {
+        case ' ': break;
+        case '1': state = state_M1;     break;
+        case '4': state = state_M4;     break;
+        default: state = state_IGNORE;
+      }
+      break;
+
+    case state_M1:
+      switch (c) {
+        case '0': state = state_M10;    break;
+        case '1': state = state_M11;    break;
+        default: state = state_IGNORE;
+      }
+      break;
+
+    case state_M10:
+      state = (c == '8') ? state_M108 : state_IGNORE;
+      break;
+
+    case state_M11:
+      state = (c == '2') ? state_M112 : state_IGNORE;
+      break;
+
+    case state_M4:
+      state = (c == '1') ? state_M41 : state_IGNORE;
+      break;
+
+    case state_M41:
+      state = (c == '0') ? state_M410 : state_IGNORE;
+      break;
+
+    case state_IGNORE:
+      if (c == '\n') state = state_RESET;
+      break;
+
+    default:
+      if (c == '\n') {
+        switch (state) {
+          case state_M108:
+          wait_for_user = wait_for_heatup = false;
+          break;
+          case state_M112:
+          kill(PSTR(MSG_KILLED));
+          break;
+          case state_M410:
+          quickstop_stepper();
+          break;
+          default:
+          break;
+        }
+        state = state_RESET;
+      }
+    }
+  }
+
+#endif // EMERGENCY_PARSER
+
+FORCE_INLINE void store_rxd_char() {
+
+  const ring_buffer_pos_t h = rx_buffer.head,
+                          i = (ring_buffer_pos_t)(h + 1) & (ring_buffer_pos_t)(RX_BUFFER_SIZE - 1);
+
+    // Read the character
+  const uint8_t c = HWUART->UART_RHR;
+
+  // If the character is to be stored at the index just before the tail
+  // (such that the head would advance to the current tail), the buffer is
+  // critical, so don't write the character or advance the head.
+  if (i != rx_buffer.tail) {
+    rx_buffer.buffer[h] = c;
+    rx_buffer.head = i;
+  }
+  #if ENABLED(SERIAL_STATS_DROPPED_RX)
+    else if (!++rx_dropped_bytes) ++rx_dropped_bytes;
+  #endif
+
+#if ENABLED(SERIAL_STATS_MAX_RX_QUEUED)
+  // calculate count of bytes stored into the RX buffer
+  ring_buffer_pos_t rx_count = (ring_buffer_pos_t)(rx_buffer.head - rx_buffer.tail) & (ring_buffer_pos_t)(RX_BUFFER_SIZE - 1);
+  // Keep track of the maximum count of enqueued bytes
+  NOLESS(rx_max_enqueued, rx_count);
+#endif
+
+#if ENABLED(SERIAL_XON_XOFF)
+
+  // for high speed transfers, we can use XON/XOFF protocol to do
+  // software handshake and avoid overruns.
+  if ((xon_xoff_state & XON_XOFF_CHAR_MASK) == XON_CHAR) {
+
+    // calculate count of bytes stored into the RX buffer
+    ring_buffer_pos_t rx_count = (ring_buffer_pos_t)(rx_buffer.head - rx_buffer.tail) & (ring_buffer_pos_t)(RX_BUFFER_SIZE - 1);
+
+    // if we are above 12.5% of RX buffer capacity, send XOFF before
+    // we run out of RX buffer space .. We need 325 bytes @ 250kbits/s to
+    // let the host react and stop sending bytes. This translates to 13mS
+    // propagation time.
+    if (rx_count >= (RX_BUFFER_SIZE) / 8) {
+      // If TX interrupts are disabled and data register is empty,
+      // just write the byte to the data register and be done. This
+      // shortcut helps significantly improve the effective datarate
+      // at high (>500kbit/s) bitrates, where interrupt overhead
+      // becomes a slowdown.
+      if (!(HWUART->UART_IMR & UART_IMR_TXRDY) && (HWUART->UART_SR & UART_SR_TXRDY)) {
+        // Send an XOFF character
+        HWUART->UART_THR = XOFF_CHAR;
+
+        // And remember it was sent
+        xon_xoff_state = XOFF_CHAR | XON_XOFF_CHAR_SENT;
+      }
+      else {
+        // TX interrupts disabled, but buffer still not empty ... or
+        // TX interrupts enabled. Reenable TX ints and schedule XOFF
+        // character to be sent
+        #if TX_BUFFER_SIZE > 0
+          HWUART->UART_IER = UART_IER_TXRDY;
+          xon_xoff_state = XOFF_CHAR;
+        #else
+          // We are not using TX interrupts, we will have to send this manually
+          while (!(HWUART->UART_SR & UART_SR_TXRDY)) { sw_barrier(); };
+          HWUART->UART_THR = XOFF_CHAR;
+          // And remember we already sent it
+          xon_xoff_state = XOFF_CHAR | XON_XOFF_CHAR_SENT;
+        #endif
+      }
+    }
+  }
+#endif // SERIAL_XON_XOFF
+
+#if ENABLED(EMERGENCY_PARSER)
+  emergency_parser(c);
+#endif
+}
+
+#if TX_BUFFER_SIZE > 0
+
+  FORCE_INLINE void _tx_thr_empty_irq(void) {
+    // If interrupts are enabled, there must be more data in the output
+    // buffer.
+
+    #if ENABLED(SERIAL_XON_XOFF)
+      // Do a priority insertion of an XON/XOFF char, if needed.
+      const uint8_t state = xon_xoff_state;
+      if (!(state & XON_XOFF_CHAR_SENT)) {
+        HWUART->UART_THR = state & XON_XOFF_CHAR_MASK;
+        xon_xoff_state = state | XON_XOFF_CHAR_SENT;
+      }
+      else
+    #endif
+      { // Send the next byte
+        const uint8_t t = tx_buffer.tail, c = tx_buffer.buffer[t];
+        tx_buffer.tail = (t + 1) & (TX_BUFFER_SIZE - 1);
+        HWUART->UART_THR = c;
+      }
+
+    // Disable interrupts if the buffer is empty
+    if (tx_buffer.head == tx_buffer.tail)
+      HWUART->UART_IDR = UART_IDR_TXRDY;
+  }
+
+#endif // TX_BUFFER_SIZE
+
+static void UART_ISR(void) {
+  uint32_t status = HWUART->UART_SR;
+
+  // Did we receive data?
+  if (status & UART_SR_RXRDY)
+    store_rxd_char();
+
+  #if TX_BUFFER_SIZE > 0
+    // Do we have something to send, and TX interrupts are enabled (meaning something to send) ?
+    if ((status & UART_SR_TXRDY) && (HWUART->UART_IMR & UART_IMR_TXRDY))
+      _tx_thr_empty_irq();
+  #endif
+
+  // Acknowledge errors
+  if ((status & UART_SR_OVRE) || (status & UART_SR_FRAME)) {
+    // TODO: error reporting outside ISR
+    HWUART->UART_CR = UART_CR_RSTSTA;
+  }
+}
+
+// Public Methods
+
+void MarlinSerial::begin(const long baud_setting) {
+
+  // Disable UART interrupt in NVIC
+  NVIC_DisableIRQ( HWUART_IRQ );
+
+  // Disable clock
+  pmc_disable_periph_clk( HWUART_IRQ_ID );
+
+  // Configure PMC
+  pmc_enable_periph_clk( HWUART_IRQ_ID );
+
+  // Disable PDC channel
+  HWUART->UART_PTCR = UART_PTCR_RXTDIS | UART_PTCR_TXTDIS;
+
+  // Reset and disable receiver and transmitter
+  HWUART->UART_CR = UART_CR_RSTRX | UART_CR_RSTTX | UART_CR_RXDIS | UART_CR_TXDIS;
+
+  // Configure mode: 8bit, No parity, 1 bit stop
+  HWUART->UART_MR = UART_MR_CHMODE_NORMAL | US_MR_CHRL_8_BIT | US_MR_NBSTOP_1_BIT | UART_MR_PAR_NO;
+
+  // Configure baudrate (asynchronous, no oversampling)
+  HWUART->UART_BRGR = (SystemCoreClock / (baud_setting << 4));
+
+  // Configure interrupts
+  HWUART->UART_IDR = 0xFFFFFFFF;
+  HWUART->UART_IER = UART_IER_RXRDY | UART_IER_OVRE | UART_IER_FRAME;
+
+  // Install interrupt handler
+  install_isr(HWUART_IRQ, UART_ISR);
+
+  // Enable UART interrupt in NVIC
+  NVIC_EnableIRQ(HWUART_IRQ);
+
+  // Enable receiver and transmitter
+  HWUART->UART_CR = UART_CR_RXEN | UART_CR_TXEN;
+
+  #if TX_BUFFER_SIZE > 0
+    _written = false;
+  #endif
+}
+
+void MarlinSerial::end() {
+  // Disable UART interrupt in NVIC
+  NVIC_DisableIRQ( HWUART_IRQ );
+
+  pmc_disable_periph_clk( HWUART_IRQ_ID );
+}
+
+void MarlinSerial::checkRx(void) {
+  if (HWUART->UART_SR & UART_SR_RXRDY) {
+    CRITICAL_SECTION_START;
+    store_rxd_char();
+    CRITICAL_SECTION_END;
+  }
+}
+
+int MarlinSerial::peek(void) {
+  CRITICAL_SECTION_START;
+  const int v = rx_buffer.head == rx_buffer.tail ? -1 : rx_buffer.buffer[rx_buffer.tail];
+  CRITICAL_SECTION_END;
+  return v;
+}
+
+int MarlinSerial::read(void) {
+  int v;
+  CRITICAL_SECTION_START;
+  const ring_buffer_pos_t t = rx_buffer.tail;
+  if (rx_buffer.head == t)
+    v = -1;
+  else {
+    v = rx_buffer.buffer[t];
+    rx_buffer.tail = (ring_buffer_pos_t)(t + 1) & (RX_BUFFER_SIZE - 1);
+
+  #if ENABLED(SERIAL_XON_XOFF)
+    if ((xon_xoff_state & XON_XOFF_CHAR_MASK) == XOFF_CHAR) {
+      // Get count of bytes in the RX buffer
+      ring_buffer_pos_t rx_count = (ring_buffer_pos_t)(rx_buffer.head - rx_buffer.tail) & (ring_buffer_pos_t)(RX_BUFFER_SIZE - 1);
+      // When below 10% of RX buffer capacity, send XON before
+      // running out of RX buffer bytes
+      if (rx_count < (RX_BUFFER_SIZE) / 10) {
+        xon_xoff_state = XON_CHAR | XON_XOFF_CHAR_SENT;
+        CRITICAL_SECTION_END;       // End critical section before returning!
+        writeNoHandshake(XON_CHAR);
+        return v;
+      }
+    }
+  #endif
+  }
+  CRITICAL_SECTION_END;
+  return v;
+}
+
+ring_buffer_pos_t MarlinSerial::available(void) {
+  CRITICAL_SECTION_START;
+  const ring_buffer_pos_t h = rx_buffer.head, t = rx_buffer.tail;
+  CRITICAL_SECTION_END;
+  return (ring_buffer_pos_t)(RX_BUFFER_SIZE + h - t) & (RX_BUFFER_SIZE - 1);
+}
+
+void MarlinSerial::flush(void) {
+  // Don't change this order of operations. If the RX interrupt occurs between
+  // reading rx_buffer_head and updating rx_buffer_tail, the previous rx_buffer_head
+  // may be written to rx_buffer_tail, making the buffer appear full rather than empty.
+  CRITICAL_SECTION_START;
+  rx_buffer.head = rx_buffer.tail;
+  CRITICAL_SECTION_END;
+
+#if ENABLED(SERIAL_XON_XOFF)
+  if ((xon_xoff_state & XON_XOFF_CHAR_MASK) == XOFF_CHAR) {
+    xon_xoff_state = XON_CHAR | XON_XOFF_CHAR_SENT;
+    writeNoHandshake(XON_CHAR);
+  }
+#endif
+}
+
+#if TX_BUFFER_SIZE > 0
+  uint8_t MarlinSerial::availableForWrite(void) {
+    CRITICAL_SECTION_START;
+    const uint8_t h = tx_buffer.head, t = tx_buffer.tail;
+    CRITICAL_SECTION_END;
+    return (uint8_t)(TX_BUFFER_SIZE + h - t) & (TX_BUFFER_SIZE - 1);
+  }
+
+  void MarlinSerial::write(const uint8_t c) {
+    #if ENABLED(SERIAL_XON_XOFF)
+      const uint8_t state = xon_xoff_state;
+      if (!(state & XON_XOFF_CHAR_SENT)) {
+        // Send 2 chars: XON/XOFF, then a user-specified char
+        writeNoHandshake(state & XON_XOFF_CHAR_MASK);
+        xon_xoff_state = state | XON_XOFF_CHAR_SENT;
+      }
+    #endif
+    writeNoHandshake(c);
+  }
+
+  void MarlinSerial::writeNoHandshake(const uint8_t c) {
+    _written = true;
+    CRITICAL_SECTION_START;
+    bool emty = (tx_buffer.head == tx_buffer.tail);
+    CRITICAL_SECTION_END;
+    // If the buffer and the data register is empty, just write the byte
+    // to the data register and be done. This shortcut helps
+    // significantly improve the effective datarate at high (>
+    // 500kbit/s) bitrates, where interrupt overhead becomes a slowdown.
+    if (emty && (HWUART->UART_SR & UART_SR_TXRDY)) {
+      CRITICAL_SECTION_START;
+        HWUART->UART_THR = c;
+        HWUART->UART_IER = UART_IER_TXRDY;
+      CRITICAL_SECTION_END;
+      return;
+    }
+    const uint8_t i = (tx_buffer.head + 1) & (TX_BUFFER_SIZE - 1);
+
+    // If the output buffer is full, there's nothing for it other than to
+    // wait for the interrupt handler to empty it a bit
+    while (i == tx_buffer.tail) {
+      if (__get_PRIMASK()) {
+        // Interrupts are disabled, so we'll have to poll the data
+        // register empty flag ourselves. If it is set, pretend an
+        // interrupt has happened and call the handler to free up
+        // space for us.
+        if (HWUART->UART_SR & UART_SR_TXRDY)
+          _tx_thr_empty_irq();
+      }
+      else {
+        // nop, the interrupt handler will free up space for us
+      }
+      sw_barrier();
+    }
+
+    tx_buffer.buffer[tx_buffer.head] = c;
+    { CRITICAL_SECTION_START;
+        tx_buffer.head = i;
+        HWUART->UART_IER = UART_IER_TXRDY;
+      CRITICAL_SECTION_END;
+    }
+    return;
+  }
+
+  void MarlinSerial::flushTX(void) {
+    // TX
+    // If we have never written a byte, no need to flush.
+    if (!_written)
+      return;
+
+    while ((HWUART->UART_IMR & UART_IMR_TXRDY) || !(HWUART->UART_SR & UART_SR_TXEMPTY)) {
+      if (__get_PRIMASK())
+        if ((HWUART->UART_SR & UART_SR_TXRDY))
+          _tx_thr_empty_irq();
+      sw_barrier();
+    }
+    // If we get here, nothing is queued anymore (TX interrupts are disabled) and
+    // the hardware finished tranmission (TXEMPTY is set).
+  }
+
+#else // TX_BUFFER_SIZE == 0
+
+  void MarlinSerial::write(const uint8_t c) {
+    #if ENABLED(SERIAL_XON_XOFF)
+      // Do a priority insertion of an XON/XOFF char, if needed.
+      const uint8_t state = xon_xoff_state;
+      if (!(state & XON_XOFF_CHAR_SENT)) {
+        writeNoHandshake(state & XON_XOFF_CHAR_MASK);
+        xon_xoff_state = state | XON_XOFF_CHAR_SENT;
+      }
+    #endif
+    writeNoHandshake(c);
+  }
+
+  void MarlinSerial::writeNoHandshake(const uint8_t c) {
+    while (!(HWUART->UART_SR & UART_SR_TXRDY)) { sw_barrier(); };
+    HWUART->UART_THR = c;
+  }
+
+#endif // TX_BUFFER_SIZE == 0
+
+/**
+* Imports from print.h
+*/
+
+void MarlinSerial::print(char c, int base) {
+  print((long)c, base);
+}
+
+void MarlinSerial::print(unsigned char b, int base) {
+  print((unsigned long)b, base);
+}
+
+void MarlinSerial::print(int n, int base) {
+  print((long)n, base);
+}
+
+void MarlinSerial::print(unsigned int n, int base) {
+  print((unsigned long)n, base);
+}
+
+void MarlinSerial::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 MarlinSerial::print(unsigned long n, int base) {
+  if (base == 0) write(n);
+  else printNumber(n, base);
+}
+
+void MarlinSerial::print(double n, int digits) {
+  printFloat(n, digits);
+}
+
+void MarlinSerial::println(void) {
+  print('\r');
+  print('\n');
+}
+
+void MarlinSerial::println(const String& s) {
+  print(s);
+  println();
+}
+
+void MarlinSerial::println(const char c[]) {
+  print(c);
+  println();
+}
+
+void MarlinSerial::println(char c, int base) {
+  print(c, base);
+  println();
+}
+
+void MarlinSerial::println(unsigned char b, int base) {
+  print(b, base);
+  println();
+}
+
+void MarlinSerial::println(int n, int base) {
+  print(n, base);
+  println();
+}
+
+void MarlinSerial::println(unsigned int n, int base) {
+  print(n, base);
+  println();
+}
+
+void MarlinSerial::println(long n, int base) {
+  print(n, base);
+  println();
+}
+
+void MarlinSerial::println(unsigned long n, int base) {
+  print(n, base);
+  println();
+}
+
+void MarlinSerial::println(double n, int digits) {
+  print(n, digits);
+  println();
+}
+
+// Private Methods
+
+void MarlinSerial::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 MarlinSerial::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;
+  for (uint8_t i = 0; i < digits; ++i)
+    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;
+    }
+  }
+}
+
+// Preinstantiate
+MarlinSerial customizedSerial;
+
+#endif // ARDUINO_ARCH_SAM

Marlin/src/HAL/HAL_DUE/MarlinSerial_Due.h

@@ -0,0 +1,142 @@
+/**
+ * Marlin 3D Printer Firmware
+ * Copyright (C) 2016 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 <http://www.gnu.org/licenses/>.
+ *
+ */
+
+/**
+ * MarlinSerial_Due.h - Hardware serial library for Arduino DUE
+ * Copyright (c) 2017 Eduardo José Tagle. All right reserved
+ * Based on MarlinSerial for AVR, copyright (c) 2006 Nicholas Zambetti.  All right reserved.
+ */
+
+#ifndef MARLINSERIAL_DUE_H
+#define MARLINSERIAL_DUE_H
+
+#include "../../inc/MarlinConfig.h"
+
+#include <WString.h>
+
+#ifndef SERIAL_PORT
+  #define SERIAL_PORT 0
+#endif
+
+#define DEC 10
+#define HEX 16
+#define OCT 8
+#define BIN 2
+#define BYTE 0
+
+// 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
+// location to which to write the next incoming character and rx_buffer_tail
+// is the index of the location from which to read.
+// 256 is the max limit due to uint8_t head and tail. Use only powers of 2. (...,16,32,64,128,256)
+#ifndef RX_BUFFER_SIZE
+  #define RX_BUFFER_SIZE 128
+#endif
+#ifndef TX_BUFFER_SIZE
+  #define TX_BUFFER_SIZE 32
+#endif
+
+#if ENABLED(SERIAL_XON_XOFF) && RX_BUFFER_SIZE < 1024
+  #error "XON/XOFF requires RX_BUFFER_SIZE >= 1024 for reliable transfers without drops."
+#endif
+
+#if !IS_POWER_OF_2(RX_BUFFER_SIZE) || RX_BUFFER_SIZE < 2
+  #error "RX_BUFFER_SIZE must be a power of 2 greater than 1."
+#endif
+
+#if TX_BUFFER_SIZE && (TX_BUFFER_SIZE < 2 || TX_BUFFER_SIZE > 256 || !IS_POWER_OF_2(TX_BUFFER_SIZE))
+  #error "TX_BUFFER_SIZE must be 0 or a power of 2 greater than 1."
+#endif
+
+#if RX_BUFFER_SIZE > 256
+  typedef uint16_t ring_buffer_pos_t;
+#else
+  typedef uint8_t ring_buffer_pos_t;
+#endif
+
+#if ENABLED(SERIAL_STATS_DROPPED_RX)
+  extern uint8_t rx_dropped_bytes;
+#endif
+
+#if ENABLED(SERIAL_STATS_MAX_RX_QUEUED)
+  extern ring_buffer_pos_t rx_max_enqueued;
+#endif
+
+class MarlinSerial {
+
+public:
+  MarlinSerial() {};
+  static void begin(const long);
+  static void end();
+  static int peek(void);
+  static int read(void);
+  static void flush(void);
+  static ring_buffer_pos_t available(void);
+  static void checkRx(void);
+  static void write(const uint8_t c);
+  #if TX_BUFFER_SIZE > 0
+    static uint8_t availableForWrite(void);
+    static void flushTX(void);
+  #endif
+  static void writeNoHandshake(const uint8_t c);
+
+  #if ENABLED(SERIAL_STATS_DROPPED_RX)
+    FORCE_INLINE static uint32_t dropped() { return rx_dropped_bytes; }
+  #endif
+
+  #if ENABLED(SERIAL_STATS_MAX_RX_QUEUED)
+    FORCE_INLINE static ring_buffer_pos_t rxMaxEnqueued() { return rx_max_enqueued; }
+  #endif
+
+  static FORCE_INLINE void write(const char* str) { while (*str) write(*str++); }
+  static FORCE_INLINE void write(const uint8_t* buffer, size_t size) { while (size--) write(*buffer++); }
+  static FORCE_INLINE void print(const String& s) { for (int i = 0; i < (int)s.length(); i++) write(s[i]); }
+  static FORCE_INLINE 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(void);
+  operator bool() { return true; }
+
+private:
+  static void printNumber(unsigned long, const uint8_t);
+  static void printFloat(double, uint8_t);
+};
+
+extern MarlinSerial customizedSerial;
+
+#endif // MARLINSERIAL_DUE_H

Marlin/src/core/serial.h

@@ -25,24 +25,10 @@
 
 #include "../inc/MarlinConfig.h"
 
-//todo: HAL: breaks encapsulation
-// For AVR only, define a serial interface based on configuration
-#ifdef __AVR__
-  #ifdef USBCON
-    #include "HardwareSerial.h"
-    #if ENABLED(BLUETOOTH)
-      #define MYSERIAL bluetoothSerial
-    #else
-      #define MYSERIAL Serial
-    #endif // BLUETOOTH
-  #else
-    #include "../HAL/HAL_AVR/MarlinSerial.h"
-    #define MYSERIAL customizedSerial
-  #endif
+#if HAS_ABL && ENABLED(DEBUG_LEVELING_FEATURE)
+  #include "../libs/vector_3.h"
 #endif
 
-#include "../libs/vector_3.h"
-
 /**
  * Define debug bit-masks
  */
@@ -58,6 +44,27 @@ enum DebugFlags {
   DEBUG_ALL           = 0xFF
 };
 
+//todo: HAL: breaks encapsulation
+// For AVR only, define a serial interface based on configuration
+#ifdef __AVR__
+  #ifdef USBCON
+    #include "HardwareSerial.h"
+    #if ENABLED(BLUETOOTH)
+      #define MYSERIAL bluetoothSerial
+    #else
+      #define MYSERIAL Serial
+    #endif // BLUETOOTH
+  #else
+    #include "../HAL/HAL_AVR/MarlinSerial.h"
+    #define MYSERIAL customizedSerial
+  #endif
+#endif
+
+#ifdef ARDUINO_ARCH_SAM
+  // To pull the Serial port definitions and overrides
+  #include "../HAL/HAL_DUE/MarlinSerial_Due.h"
+#endif
+
 extern uint8_t marlin_debug_flags;
 #define DEBUGGING(F) (marlin_debug_flags & (DEBUG_## F))