Quadrotor

/*

 Servo.cpp - Interrupt driven Servo library for Arduino using 16 bit timers- Version 2

 Copyright (c) 2009 Michael Margolis.  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

 */

/* 

 A servo is activated by creating an instance of the Servo class passing the desired pin to the attach() method.

 The servos are pulsed in the background using the value most recently written using the write() method

 Note that analogWrite of PWM on pins associated with the timer are disabled when the first servo is attached.

 Timers are seized as needed in groups of 12 servos - 24 servos use two timers, 48 servos will use four.

 The methods are:

 Servo - Class for manipulating servo motors connected to Arduino pins.

 attach(pin )  - Attaches a servo motor to an i/o pin.

 attach(pin, min, max  ) - Attaches to a pin setting min and max values in microseconds

 default min is 544, max is 2400  

 write()     - Sets the servo angle in degrees.  (invalid angle that is valid as pulse in microseconds is treated as microseconds)

 writeMicroseconds() - Sets the servo pulse width in microseconds 

 read()      - Gets the last written servo pulse width as an angle between 0 and 180. 

 readMicroseconds()   - Gets the last written servo pulse width in microseconds. (was read_us() in first release)

 attached()  - Returns true if there is a servo attached. 

 detach()    - Stops an attached servos from pulsing its i/o pin. 

*/

#include <avr/interrupt.h>

#include <Arduino.h> 

#include "Servo.h"

#define usToTicks(_us)    (( clockCyclesPerMicrosecond()* _us) / 8)     // converts microseconds to tick (assumes prescale of 8)  // 12 Aug 2009

#define ticksToUs(_ticks) (( (unsigned)_ticks * 8)/ clockCyclesPerMicrosecond() ) // converts from ticks back to microseconds

#define TRIM_DURATION       2                               // compensation ticks to trim adjust for digitalWrite delays // 12 August 2009

//#define NBR_TIMERS        (MAX_SERVOS / SERVOS_PER_TIMER)

static servo_t servos[MAX_SERVOS];                          // static array of servo structures

static volatile int8_t Channel[_Nbr_16timers ];             // counter for the servo being pulsed for each timer (or -1 if refresh interval)

uint8_t ServoCount = 0;                                     // the total number of attached servos

// convenience macros

#define SERVO_INDEX_TO_TIMER(_servo_nbr) ((timer16_Sequence_t)(_servo_nbr / SERVOS_PER_TIMER)) // returns the timer controlling this servo

#define SERVO_INDEX_TO_CHANNEL(_servo_nbr) (_servo_nbr % SERVOS_PER_TIMER)       // returns the index of the servo on this timer

#define SERVO_INDEX(_timer,_channel)  ((_timer*SERVOS_PER_TIMER) + _channel)     // macro to access servo index by timer and channel

#define SERVO(_timer,_channel)  (servos[SERVO_INDEX(_timer,_channel)])            // macro to access servo class by timer and channel

#define SERVO_MIN() (MIN_PULSE_WIDTH - this->min * 4)  // minimum value in uS for this servo

#define SERVO_MAX() (MAX_PULSE_WIDTH - this->max * 4)  // maximum value in uS for this servo 

/************ static functions common to all instances ***********************/

static inline void handle_interrupts(timer16_Sequence_t timer, volatile uint16_t *TCNTn, volatile uint16_t* OCRnA)

{

  if( Channel[timer] < 0 )

    *TCNTn = 0; // channel set to -1 indicated that refresh interval completed so reset the timer 

  else{

    if( SERVO_INDEX(timer,Channel[timer]) < ServoCount && SERVO(timer,Channel[timer]).Pin.isActive == true )  

      digitalWrite( SERVO(timer,Channel[timer]).Pin.nbr,LOW); // pulse this channel low if activated   

  }

  Channel[timer]++;    // increment to the next channel

  if( SERVO_INDEX(timer,Channel[timer]) < ServoCount && Channel[timer] < SERVOS_PER_TIMER) {

    *OCRnA = *TCNTn + SERVO(timer,Channel[timer]).ticks;

    if(SERVO(timer,Channel[timer]).Pin.isActive == true)     // check if activated

      digitalWrite( SERVO(timer,Channel[timer]).Pin.nbr,HIGH); // its an active channel so pulse it high   

  }  

  else { 

    // finished all channels so wait for the refresh period to expire before starting over 

    if( (unsigned)*TCNTn <  (usToTicks(REFRESH_INTERVAL) + 4) )  // allow a few ticks to ensure the next OCR1A not missed

      *OCRnA = (unsigned int)usToTicks(REFRESH_INTERVAL);  

    else 

      *OCRnA = *TCNTn + 4;  // at least REFRESH_INTERVAL has elapsed

    Channel[timer] = -1; // this will get incremented at the end of the refresh period to start again at the first channel

  }

}

#ifndef WIRING // Wiring pre-defines signal handlers so don't define any if compiling for the Wiring platform

// Interrupt handlers for Arduino 

#if defined(_useTimer1)

SIGNAL (TIMER1_COMPA_vect) 

{ 

  handle_interrupts(_timer1, &TCNT1, &OCR1A); 

}

#endif

#if defined(_useTimer3)

SIGNAL (TIMER3_COMPA_vect) 

{ 

  handle_interrupts(_timer3, &TCNT3, &OCR3A); 

}

#endif

#if defined(_useTimer4)

SIGNAL (TIMER4_COMPA_vect) 

{

  handle_interrupts(_timer4, &TCNT4, &OCR4A); 

}

#endif

#if defined(_useTimer5)

SIGNAL (TIMER5_COMPA_vect) 

{

  handle_interrupts(_timer5, &TCNT5, &OCR5A); 

}

#endif

#elif defined WIRING

// Interrupt handlers for Wiring 

#if defined(_useTimer1)

void Timer1Service() 

{ 

  handle_interrupts(_timer1, &TCNT1, &OCR1A); 

}

#endif

#if defined(_useTimer3)

void Timer3Service() 

{ 

  handle_interrupts(_timer3, &TCNT3, &OCR3A); 

}

#endif

#endif

static void initISR(timer16_Sequence_t timer)

{  

#if defined (_useTimer1)

  if(timer == _timer1) {

    TCCR1A = 0;             // normal counting mode 

    TCCR1B = _BV(CS11);     // set prescaler of 8 

    TCNT1 = 0;              // clear the timer count 

#if defined(__AVR_ATmega8__)|| defined(__AVR_ATmega128__)

    TIFR |= _BV(OCF1A);      // clear any pending interrupts; 

    TIMSK |=  _BV(OCIE1A) ;  // enable the output compare interrupt  

#else

    // here if not ATmega8 or ATmega128

    TIFR1 |= _BV(OCF1A);     // clear any pending interrupts; 

    TIMSK1 |=  _BV(OCIE1A) ; // enable the output compare interrupt 

#endif    

#if defined(WIRING)       

    timerAttach(TIMER1OUTCOMPAREA_INT, Timer1Service); 

#endif        

  } 

#endif  

#if defined (_useTimer3)

  if(timer == _timer3) {

    TCCR3A = 0;             // normal counting mode 

    TCCR3B = _BV(CS31);     // set prescaler of 8  

    TCNT3 = 0;              // clear the timer count 

#if defined(__AVR_ATmega128__)

    TIFR |= _BV(OCF3A);     // clear any pending interrupts;   

        ETIMSK |= _BV(OCIE3A);  // enable the output compare interrupt     

#else  

    TIFR3 = _BV(OCF3A);     // clear any pending interrupts; 

    TIMSK3 =  _BV(OCIE3A) ; // enable the output compare interrupt      

#endif

#if defined(WIRING)    

    timerAttach(TIMER3OUTCOMPAREA_INT, Timer3Service);  // for Wiring platform only        

#endif  

  }

#endif

#if defined (_useTimer4)

  if(timer == _timer4) {

    TCCR4A = 0;             // normal counting mode 

    TCCR4B = _BV(CS41);     // set prescaler of 8  

    TCNT4 = 0;              // clear the timer count 

    TIFR4 = _BV(OCF4A);     // clear any pending interrupts; 

    TIMSK4 =  _BV(OCIE4A) ; // enable the output compare interrupt

  }    

#endif

#if defined (_useTimer5)

  if(timer == _timer5) {

    TCCR5A = 0;             // normal counting mode 

    TCCR5B = _BV(CS51);     // set prescaler of 8  

    TCNT5 = 0;              // clear the timer count 

    TIFR5 = _BV(OCF5A);     // clear any pending interrupts; 

    TIMSK5 =  _BV(OCIE5A) ; // enable the output compare interrupt      

  }

#endif

} 

static void finISR(timer16_Sequence_t timer)

{

    //disable use of the given timer

#if defined WIRING   // Wiring

  if(timer == _timer1) {

    #if defined(__AVR_ATmega1281__)||defined(__AVR_ATmega2561__)

    TIMSK1 &=  ~_BV(OCIE1A) ;  // disable timer 1 output compare interrupt

    #else 

    TIMSK &=  ~_BV(OCIE1A) ;  // disable timer 1 output compare interrupt   

    #endif

    timerDetach(TIMER1OUTCOMPAREA_INT); 

  }

  else if(timer == _timer3) {     

    #if defined(__AVR_ATmega1281__)||defined(__AVR_ATmega2561__)

    TIMSK3 &= ~_BV(OCIE3A);    // disable the timer3 output compare A interrupt

    #else

    ETIMSK &= ~_BV(OCIE3A);    // disable the timer3 output compare A interrupt

    #endif

    timerDetach(TIMER3OUTCOMPAREA_INT);

  }

#else

    //For arduino - in future: call here to a currently undefined function to reset the timer

#endif

}

static boolean isTimerActive(timer16_Sequence_t timer)

{

  // returns true if any servo is active on this timer

  for(uint8_t channel=0; channel < SERVOS_PER_TIMER; channel++) {

    if(SERVO(timer,channel).Pin.isActive == true)

      return true;

  }

  return false;

}

/****************** end of static functions ******************************/

Servo::Servo()

{

  if( ServoCount < MAX_SERVOS) {

    this->servoIndex = ServoCount++;                    // assign a servo index to this instance

        servos[this->servoIndex].ticks = usToTicks(DEFAULT_PULSE_WIDTH);   // store default values  - 12 Aug 2009

  }

  else

    this->servoIndex = INVALID_SERVO ;  // too many servos 

}

uint8_t Servo::attach(int pin)

{

  return this->attach(pin, MIN_PULSE_WIDTH, MAX_PULSE_WIDTH);

}

uint8_t Servo::attach(int pin, int min, int max)

{

  if(this->servoIndex < MAX_SERVOS ) {

    pinMode( pin, OUTPUT) ;                                   // set servo pin to output

    servos[this->servoIndex].Pin.nbr = pin;  

    // todo min/max check: abs(min - MIN_PULSE_WIDTH) /4 < 128 

    this->min  = (MIN_PULSE_WIDTH - min)/4; //resolution of min/max is 4 uS

    this->max  = (MAX_PULSE_WIDTH - max)/4; 

    // initialize the timer if it has not already been initialized 

    timer16_Sequence_t timer = SERVO_INDEX_TO_TIMER(servoIndex);

    if(isTimerActive(timer) == false)

      initISR(timer);    

    servos[this->servoIndex].Pin.isActive = true;  // this must be set after the check for isTimerActive

  } 

  return this->servoIndex ;

}

void Servo::detach()  

{

  servos[this->servoIndex].Pin.isActive = false;  

  timer16_Sequence_t timer = SERVO_INDEX_TO_TIMER(servoIndex);

  if(isTimerActive(timer) == false) {

    finISR(timer);

  }

}

void Servo::write(int value)

{  

  if(value < MIN_PULSE_WIDTH)

  {  // treat values less than 544 as angles in degrees (valid values in microseconds are handled as microseconds)

    if(value < 0) value = 0;

    if(value > 180) value = 180;

    value = map(value, 0, 180, SERVO_MIN(),  SERVO_MAX());      

  }

  this->writeMicroseconds(value);

}

void Servo::writeMicroseconds(int value)

{

  // calculate and store the values for the given channel

  byte channel = this->servoIndex;

  if( (channel >= 0) && (channel < MAX_SERVOS) )   // ensure channel is valid

  {  

    if( value < SERVO_MIN() )          // ensure pulse width is valid

      value = SERVO_MIN();

    else if( value > SERVO_MAX() )

      value = SERVO_MAX();   

          value = value - TRIM_DURATION;

    value = usToTicks(value);  // convert to ticks after compensating for interrupt overhead - 12 Aug 2009

    uint8_t oldSREG = SREG;

    cli();

    servos[channel].ticks = value;  

    SREG = oldSREG;   

  } 

}

int Servo::read() // return the value as degrees

{

  return  map( this->readMicroseconds()+1, SERVO_MIN(), SERVO_MAX(), 0, 180);     

}

int Servo::readMicroseconds()

{

  unsigned int pulsewidth;

  if( this->servoIndex != INVALID_SERVO )

    pulsewidth = ticksToUs(servos[this->servoIndex].ticks)  + TRIM_DURATION ;   // 12 aug 2009

  else 

    pulsewidth  = 0;

  return pulsewidth;   

}

bool Servo::attached()

{

  return servos[this->servoIndex].Pin.isActive ;

}