text: /*
    NeoHWSerial.h - Hardware serial library with attachInterrupt
    Copyright (c) 2006 Nicholas Zambetti.  All right reserved.
  
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.
  
    This library 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
    Lesser General Public License for more details.
  
    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  
    Modified 28 September 2010 by Mark Sproul
    Modified 14 August 2012 by Alarus
    Modified 3 December 2013 by Matthijs Kooijman
    Modified 2 November 2015 by SlashDev
  */
  
  #ifndef NeoHWSerial_h
  #define NeoHWSerial_h
  
  #include <inttypes.h>
  
  #include "Stream.h"
  
  // Define constants and variables for buffering incoming serial data.  We're
  // using a ring buffer (I think), in which head is the index of the location
  // to which to write the next incoming character and tail is the index of the
  // location from which to read.
  // NOTE: a "power of 2" buffer size is reccomended to dramatically
  //       optimize all the modulo operations for ring buffers.
  #if !defined(SERIAL_TX_BUFFER_SIZE)
  #if (RAMEND < 1000)
  #define SERIAL_TX_BUFFER_SIZE 16
  #else
  #define SERIAL_TX_BUFFER_SIZE 64
  #endif
  #endif
  #if !defined(SERIAL_RX_BUFFER_SIZE)
  #if (RAMEND < 1000)
  #define SERIAL_RX_BUFFER_SIZE 16
  #else
  #define SERIAL_RX_BUFFER_SIZE 64
  #endif
  #endif
  #if (SERIAL_TX_BUFFER_SIZE>256)
  typedef uint16_t tx_buffer_index_t;
  #else
  typedef uint8_t tx_buffer_index_t;
  #endif
  #if  (SERIAL_RX_BUFFER_SIZE>256)
  typedef uint16_t rx_buffer_index_t;
  #else
  typedef uint8_t rx_buffer_index_t;
  #endif
  
  // Define config for Serial.begin(baud, config);
  #define SERIAL_5N1 0x00
  #define SERIAL_6N1 0x02
  #define SERIAL_7N1 0x04
  #define SERIAL_8N1 0x06
  #define SERIAL_5N2 0x08
  #define SERIAL_6N2 0x0A
  #define SERIAL_7N2 0x0C
  #define SERIAL_8N2 0x0E
  #define SERIAL_5E1 0x20
  #define SERIAL_6E1 0x22
  #define SERIAL_7E1 0x24
  #define SERIAL_8E1 0x26
  #define SERIAL_5E2 0x28
  #define SERIAL_6E2 0x2A
  #define SERIAL_7E2 0x2C
  #define SERIAL_8E2 0x2E
  #define SERIAL_5O1 0x30
  #define SERIAL_6O1 0x32
  #define SERIAL_7O1 0x34
  #define SERIAL_8O1 0x36
  #define SERIAL_5O2 0x38
  #define SERIAL_6O2 0x3A
  #define SERIAL_7O2 0x3C
  #define SERIAL_8O2 0x3E
  
  class NeoHWSerial : public Stream
  {
    protected:
      volatile uint8_t * const _ubrrh;
      volatile uint8_t * const _ubrrl;
      volatile uint8_t * const _ucsra;
      volatile uint8_t * const _ucsrb;
      volatile uint8_t * const _ucsrc;
      volatile uint8_t * const _udr;
      // Has any byte been written to the UART since begin()
      bool _written;
  
      volatile rx_buffer_index_t _rx_buffer_head;
      volatile rx_buffer_index_t _rx_buffer_tail;
      volatile tx_buffer_index_t _tx_buffer_head;
      volatile tx_buffer_index_t _tx_buffer_tail;
  
      // Don't put any members after these buffers, since only the first
      // 32 bytes of this struct can be accessed quickly using the ldd
      // instruction.
      unsigned char _rx_buffer[SERIAL_RX_BUFFER_SIZE];
      unsigned char _tx_buffer[SERIAL_TX_BUFFER_SIZE];
  
    public:
      inline NeoHWSerial(
        volatile uint8_t *ubrrh, volatile uint8_t *ubrrl,
        volatile uint8_t *ucsra, volatile uint8_t *ucsrb,
        volatile uint8_t *ucsrc, volatile uint8_t *udr);
      void begin(unsigned long baud) { begin(baud, SERIAL_8N1); }
      void begin(unsigned long, uint8_t);
      void end();
      virtual int available(void);
      virtual int peek(void);
      virtual int read(void);
      int availableForWrite(void);
      virtual void flush(void);
      virtual size_t write(uint8_t);
      inline size_t write(unsigned long n) { return write((uint8_t)n); }
      inline size_t write(long n) { return write((uint8_t)n); }
      inline size_t write(unsigned int n) { return write((uint8_t)n); }
      inline size_t write(int n) { return write((uint8_t)n); }
      using Print::write; // pull in write(str) and write(buf, size) from Print
      operator bool() { return true; }
  
      // Interrupt handlers - Not intended to be called externally
      inline void _rx_complete_irq(void);
      void _tx_udr_empty_irq(void);
  
      typedef void (* isr_t)( uint8_t );
      void attachInterrupt( isr_t fn );
      void detachInterrupt() { attachInterrupt( (isr_t) NULL ); };
    private:
      isr_t  _isr;
  
      NeoHWSerial( const NeoHWSerial & );
      NeoHWSerial & operator =( const NeoHWSerial &);
  };
  
  #if defined(UBRRH) || defined(UBRR0H)
    extern NeoHWSerial NeoSerial;
    #define HAVE_HWSERIAL0
  #endif
  #if defined(UBRR1H)
    extern NeoHWSerial NeoSerial1;
    #define HAVE_HWSERIAL1
  #endif
  #if defined(UBRR2H)
    extern NeoHWSerial NeoSerial2;
    #define HAVE_HWSERIAL2
  #endif
  #if defined(UBRR3H)
    extern NeoHWSerial NeoSerial3;
    #define HAVE_HWSERIAL3
  #endif
  
  #endif
  