Quadrotor

/*

SoftwareSerial.cpp (formerly NewSoftSerial.cpp) - 

Multi-instance software serial library for Arduino/Wiring

-- Interrupt-driven receive and other improvements by ladyada

   (http://ladyada.net)

-- Tuning, circular buffer, derivation from class Print/Stream,

   multi-instance support, porting to 8MHz processors,

   various optimizations, PROGMEM delay tables, inverse logic and 

   direct port writing by Mikal Hart (http://www.arduiniana.org)

-- Pin change interrupt macros by Paul Stoffregen (http://www.pjrc.com)

-- 20MHz processor support by Garrett Mace (http://www.macetech.com)

-- ATmega1280/2560 support by Brett Hagman (http://www.roguerobotics.com/)

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

The latest version of this library can always be found at

http://arduiniana.org.

*/

// When set, _DEBUG co-opts pins 11 and 13 for debugging with an

// oscilloscope or logic analyzer.  Beware: it also slightly modifies

// the bit times, so don't rely on it too much at high baud rates

#define _DEBUG 0

#define _DEBUG_PIN1 11

#define _DEBUG_PIN2 13

// 

// Includes

// 

#include <avr/interrupt.h>

#include <avr/pgmspace.h>

#include "Arduino.h"

#include "SoftwareSerial.h"

//

// Lookup table

//

typedef struct _DELAY_TABLE

{

  long baud;

  unsigned short rx_delay_centering;

  unsigned short rx_delay_intrabit;

  unsigned short rx_delay_stopbit;

  unsigned short tx_delay;

} DELAY_TABLE;

#if F_CPU == 16000000

static const DELAY_TABLE PROGMEM table[] = 

{

  //  baud    rxcenter   rxintra    rxstop    tx

  { 115200,   1,         17,        17,       12,    },

  { 57600,    10,        37,        37,       33,    },

  { 38400,    25,        57,        57,       54,    },

  { 31250,    31,        70,        70,       68,    },

  { 28800,    34,        77,        77,       74,    },

  { 19200,    54,        117,       117,      114,   },

  { 14400,    74,        156,       156,      153,   },

  { 9600,     114,       236,       236,      233,   },

  { 4800,     233,       474,       474,      471,   },

  { 2400,     471,       950,       950,      947,   },

  { 1200,     947,       1902,      1902,     1899,  },

  { 300,      3804,      7617,      7617,     7614,  },

};

const int XMIT_START_ADJUSTMENT = 5;

#elif F_CPU == 8000000

static const DELAY_TABLE table[] PROGMEM = 

{

  //  baud    rxcenter    rxintra    rxstop  tx

  { 115200,   1,          5,         5,      3,      },

  { 57600,    1,          15,        15,     13,     },

  { 38400,    2,          25,        26,     23,     },

  { 31250,    7,          32,        33,     29,     },

  { 28800,    11,         35,        35,     32,     },

  { 19200,    20,         55,        55,     52,     },

  { 14400,    30,         75,        75,     72,     },

  { 9600,     50,         114,       114,    112,    },

  { 4800,     110,        233,       233,    230,    },

  { 2400,     229,        472,       472,    469,    },

  { 1200,     467,        948,       948,    945,    },

  { 300,      1895,       3805,      3805,   3802,   },

};

const int XMIT_START_ADJUSTMENT = 4;

#elif F_CPU == 20000000

// 20MHz support courtesy of the good people at macegr.com.

// Thanks, Garrett!

static const DELAY_TABLE PROGMEM table[] =

{

  //  baud    rxcenter    rxintra    rxstop  tx

  { 115200,   3,          21,        21,     18,     },

  { 57600,    20,         43,        43,     41,     },

  { 38400,    37,         73,        73,     70,     },

  { 31250,    45,         89,        89,     88,     },

  { 28800,    46,         98,        98,     95,     },

  { 19200,    71,         148,       148,    145,    },

  { 14400,    96,         197,       197,    194,    },

  { 9600,     146,        297,       297,    294,    },

  { 4800,     296,        595,       595,    592,    },

  { 2400,     592,        1189,      1189,   1186,   },

  { 1200,     1187,       2379,      2379,   2376,   },

  { 300,      4759,       9523,      9523,   9520,   },

};

const int XMIT_START_ADJUSTMENT = 6;

#else

#error This version of SoftwareSerial supports only 20, 16 and 8MHz processors

#endif

//

// Statics

//

SoftwareSerial *SoftwareSerial::active_object = 0;

char SoftwareSerial::_receive_buffer[_SS_MAX_RX_BUFF]; 

volatile uint8_t SoftwareSerial::_receive_buffer_tail = 0;

volatile uint8_t SoftwareSerial::_receive_buffer_head = 0;

//

// Debugging

//

// This function generates a brief pulse

// for debugging or measuring on an oscilloscope.

inline void DebugPulse(uint8_t pin, uint8_t count)

{

#if _DEBUG

  volatile uint8_t *pport = portOutputRegister(digitalPinToPort(pin));

  uint8_t val = *pport;

  while (count--)

  {

    *pport = val | digitalPinToBitMask(pin);

    *pport = val;

  }

#endif

}

//

// Private methods

//

/* static */ 

inline void SoftwareSerial::tunedDelay(uint16_t delay) { 

  uint8_t tmp=0;

  asm volatile("sbiw    %0, 0x01 \n\t"

    "ldi %1, 0xFF \n\t"

    "cpi %A0, 0xFF \n\t"

    "cpc %B0, %1 \n\t"

    "brne .-10 \n\t"

    : "+r" (delay), "+a" (tmp)

    : "0" (delay)

    );

}

// This function sets the current object as the "listening"

// one and returns true if it replaces another 

bool SoftwareSerial::listen()

{

  if (active_object != this)

  {

    _buffer_overflow = false;

    uint8_t oldSREG = SREG;

    cli();

    _receive_buffer_head = _receive_buffer_tail = 0;

    active_object = this;

    SREG = oldSREG;

    return true;

  }

  return false;

}

//

// The receive routine called by the interrupt handler

//

void SoftwareSerial::recv()

{

#if GCC_VERSION < 40302

// Work-around for avr-gcc 4.3.0 OSX version bug

// Preserve the registers that the compiler misses

// (courtesy of Arduino forum user *etracer*)

  asm volatile(

    "push r18 \n\t"

    "push r19 \n\t"

    "push r20 \n\t"

    "push r21 \n\t"

    "push r22 \n\t"

    "push r23 \n\t"

    "push r26 \n\t"

    "push r27 \n\t"

    ::);

#endif  

  uint8_t d = 0;

  // If RX line is high, then we don't see any start bit

  // so interrupt is probably not for us

  if (_inverse_logic ? rx_pin_read() : !rx_pin_read())

  {

    // Wait approximately 1/2 of a bit width to "center" the sample

    tunedDelay(_rx_delay_centering);

    DebugPulse(_DEBUG_PIN2, 1);

    // Read each of the 8 bits

    for (uint8_t i=0x1; i; i <<= 1)

    {

      tunedDelay(_rx_delay_intrabit);

      DebugPulse(_DEBUG_PIN2, 1);

      uint8_t noti = ~i;

      if (rx_pin_read())

        d |= i;

      else // else clause added to ensure function timing is ~balanced

        d &= noti;

    }

    // skip the stop bit

    tunedDelay(_rx_delay_stopbit);

    DebugPulse(_DEBUG_PIN2, 1);

    if (_inverse_logic)

      d = ~d;

    // if buffer full, set the overflow flag and return

    if ((_receive_buffer_tail + 1) % _SS_MAX_RX_BUFF != _receive_buffer_head) 

    {

      // save new data in buffer: tail points to where byte goes

      _receive_buffer[_receive_buffer_tail] = d; // save new byte

      _receive_buffer_tail = (_receive_buffer_tail + 1) % _SS_MAX_RX_BUFF;

    } 

    else 

    {

#if _DEBUG // for scope: pulse pin as overflow indictator

      DebugPulse(_DEBUG_PIN1, 1);

#endif

      _buffer_overflow = true;

    }

  }

#if GCC_VERSION < 40302

// Work-around for avr-gcc 4.3.0 OSX version bug

// Restore the registers that the compiler misses

  asm volatile(

    "pop r27 \n\t"

    "pop r26 \n\t"

    "pop r23 \n\t"

    "pop r22 \n\t"

    "pop r21 \n\t"

    "pop r20 \n\t"

    "pop r19 \n\t"

    "pop r18 \n\t"

    ::);

#endif

}

void SoftwareSerial::tx_pin_write(uint8_t pin_state)

{

  if (pin_state == LOW)

    *_transmitPortRegister &= ~_transmitBitMask;

  else

    *_transmitPortRegister |= _transmitBitMask;

}

uint8_t SoftwareSerial::rx_pin_read()

{

  return *_receivePortRegister & _receiveBitMask;

}

//

// Interrupt handling

//

/* static */

inline void SoftwareSerial::handle_interrupt()

{

  if (active_object)

  {

    active_object->recv();

  }

}

#if defined(PCINT0_vect)

ISR(PCINT0_vect)

{

  SoftwareSerial::handle_interrupt();

}

#endif

#if defined(PCINT1_vect)

ISR(PCINT1_vect)

{

  SoftwareSerial::handle_interrupt();

}

#endif

#if defined(PCINT2_vect)

ISR(PCINT2_vect)

{

  SoftwareSerial::handle_interrupt();

}

#endif

#if defined(PCINT3_vect)

ISR(PCINT3_vect)

{

  SoftwareSerial::handle_interrupt();

}

#endif

//

// Constructor

//

SoftwareSerial::SoftwareSerial(uint8_t receivePin, uint8_t transmitPin, bool inverse_logic /* = false */) : 

  _rx_delay_centering(0),

  _rx_delay_intrabit(0),

  _rx_delay_stopbit(0),

  _tx_delay(0),

  _buffer_overflow(false),

  _inverse_logic(inverse_logic)

{

  setTX(transmitPin);

  setRX(receivePin);

}

//

// Destructor

//

SoftwareSerial::~SoftwareSerial()

{

  end();

}

void SoftwareSerial::setTX(uint8_t tx)

{

  pinMode(tx, OUTPUT);

  digitalWrite(tx, HIGH);

  _transmitBitMask = digitalPinToBitMask(tx);

  uint8_t port = digitalPinToPort(tx);

  _transmitPortRegister = portOutputRegister(port);

}

void SoftwareSerial::setRX(uint8_t rx)

{

  pinMode(rx, INPUT);

  if (!_inverse_logic)

    digitalWrite(rx, HIGH);  // pullup for normal logic!

  _receivePin = rx;

  _receiveBitMask = digitalPinToBitMask(rx);

  uint8_t port = digitalPinToPort(rx);

  _receivePortRegister = portInputRegister(port);

}

//

// Public methods

//

void SoftwareSerial::begin(long speed)

{

  _rx_delay_centering = _rx_delay_intrabit = _rx_delay_stopbit = _tx_delay = 0;

  for (unsigned i=0; i<sizeof(table)/sizeof(table[0]); ++i)

  {

    long baud = pgm_read_dword(&table[i].baud);

    if (baud == speed)

    {

      _rx_delay_centering = pgm_read_word(&table[i].rx_delay_centering);

      _rx_delay_intrabit = pgm_read_word(&table[i].rx_delay_intrabit);

      _rx_delay_stopbit = pgm_read_word(&table[i].rx_delay_stopbit);

      _tx_delay = pgm_read_word(&table[i].tx_delay);

      break;

    }

  }

  // Set up RX interrupts, but only if we have a valid RX baud rate

  if (_rx_delay_stopbit)

  {

    if (digitalPinToPCICR(_receivePin))

    {

      *digitalPinToPCICR(_receivePin) |= _BV(digitalPinToPCICRbit(_receivePin));

      *digitalPinToPCMSK(_receivePin) |= _BV(digitalPinToPCMSKbit(_receivePin));

    }

    tunedDelay(_tx_delay); // if we were low this establishes the end

  }

#if _DEBUG

  pinMode(_DEBUG_PIN1, OUTPUT);

  pinMode(_DEBUG_PIN2, OUTPUT);

#endif

  listen();

}

void SoftwareSerial::end()

{

  if (digitalPinToPCMSK(_receivePin))

    *digitalPinToPCMSK(_receivePin) &= ~_BV(digitalPinToPCMSKbit(_receivePin));

}

// Read data from buffer

int SoftwareSerial::read()

{

  if (!isListening())

    return -1;

  // Empty buffer?

  if (_receive_buffer_head == _receive_buffer_tail)

    return -1;

  // Read from "head"

  uint8_t d = _receive_buffer[_receive_buffer_head]; // grab next byte

  _receive_buffer_head = (_receive_buffer_head + 1) % _SS_MAX_RX_BUFF;

  return d;

}

int SoftwareSerial::available()

{

  if (!isListening())

    return 0;

  return (_receive_buffer_tail + _SS_MAX_RX_BUFF - _receive_buffer_head) % _SS_MAX_RX_BUFF;

}

size_t SoftwareSerial::write(uint8_t b)

{

  if (_tx_delay == 0) {

    setWriteError();

    return 0;

  }

  uint8_t oldSREG = SREG;

  cli();  // turn off interrupts for a clean txmit

  // Write the start bit

  tx_pin_write(_inverse_logic ? HIGH : LOW);

  tunedDelay(_tx_delay + XMIT_START_ADJUSTMENT);

  // Write each of the 8 bits

  if (_inverse_logic)

  {

    for (byte mask = 0x01; mask; mask <<= 1)

    {

      if (b & mask) // choose bit

        tx_pin_write(LOW); // send 1

      else

        tx_pin_write(HIGH); // send 0

      tunedDelay(_tx_delay);

    }

    tx_pin_write(LOW); // restore pin to natural state

  }

  else

  {

    for (byte mask = 0x01; mask; mask <<= 1)

    {

      if (b & mask) // choose bit

        tx_pin_write(HIGH); // send 1

      else

        tx_pin_write(LOW); // send 0

      tunedDelay(_tx_delay);

    }

    tx_pin_write(HIGH); // restore pin to natural state

  }

  SREG = oldSREG; // turn interrupts back on

  tunedDelay(_tx_delay);

  return 1;

}

void SoftwareSerial::flush()

{

  if (!isListening())

    return;

  uint8_t oldSREG = SREG;

  cli();

  _receive_buffer_head = _receive_buffer_tail = 0;

  SREG = oldSREG;

}

int SoftwareSerial::peek()

{

  if (!isListening())

    return -1;

  // Empty buffer?

  if (_receive_buffer_head == _receive_buffer_tail)

    return -1;

  // Read from "head"

  return _receive_buffer[_receive_buffer_head];

}