eagle_Servo.h

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#ifndef EAGLE_EBOARD_HELPLIB_SERVO
    #define EAGLE_EBOARD_HELPLIB_SERVO


//=====================================================================================================================================================
//                                                                  Macro Definitions                                                                  
//=====================================================================================================================================================

  //import servo-class
  //shameless copy paste :D

  #define _useTimer1
  typedef enum { _timer1, _Nbr_16timers } timer16_Sequence_t;
  #define MIN_PULSE_WIDTH       544     // the shortest pulse sent to a servo
  #define MAX_PULSE_WIDTH      2400     // the longest pulse sent to a servo
  #define DEFAULT_PULSE_WIDTH  1500     // default pulse width when servo is attached
  #define REFRESH_INTERVAL    20000     // minumim time to refresh servos in microseconds

  #define SERVOS_PER_TIMER       12     // the maximum number of servos controlled by one timer
  #define MAX_SERVOS   (_Nbr_16timers  * SERVOS_PER_TIMER)

  #define INVALID_SERVO         255     // flag indicating an invalid servo index

//=====================================================================================================================================================
//                                                                     ServoPin_t                                                                      
//=====================================================================================================================================================

  typedef struct  {
    uint8_t nbr        :6 ;             // a pin number from 0 to 63
    uint8_t isActive   :1 ;             // true if this channel is enabled, pin not pulsed if false
  } ServoPin_t;

//=====================================================================================================================================================
//                                                                       Servo_t                                                                       
//=====================================================================================================================================================

  typedef struct {
    ServoPin_t Pin;
    volatile unsigned int ticks;
  } servo_t;

//=====================================================================================================================================================
//                                                                        Servo                                                                        
//=====================================================================================================================================================

    //-------------------------------------------------------------------------------------------------------------------------------------------------
    //                                                                    class                                                                        
    //-------------------------------------------------------------------------------------------------------------------------------------------------


  class Servo {
    public:
      Servo();
        uint8_t attach(int pin);           // attach the given pin to the next free channel, sets pinMode, returns channel number or 0 if failure
        uint8_t attach(int pin, int min, int max); // as above but also sets min and max values for writes.
        void detach();
        void write(int value);             // if value is < 200 its treated as an angle, otherwise as pulse width in microseconds
        void writeMicroseconds(int value); // Write pulse width in microseconds
        inline int read();                        // returns current pulse width as an angle between 0 and 180 degrees
        int readMicroseconds();            // returns current pulse width in microseconds for this servo (was read_us() in first release)
        inline bool attached();                   // return true if this servo is attached, otherwise false
    private:
       uint8_t servoIndex;               // index into the channel data for this servo
       int8_t min;                       // minimum is this value times 4 added to MIN_PULSE_WIDTH
       int8_t max;                       // maximum is this value times 4 added to MAX_PULSE_WIDTH
  };

    //-------------------------------------------------------------------------------------------------------------------------------------------------
    //                                                                definitions                                                                      
    //-------------------------------------------------------------------------------------------------------------------------------------------------

  #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

  
  //========= TIMER 
  
    static void initISR(timer16_Sequence_t timer) {
    if(timer == _timer1) {
      TCCR1A = 0;             // normal counting mode
      TCCR1B = _BV(CS11);     // set prescaler of 8
      TCNT1 = 0;              // clear the timer count
      TIFR1 |= _BV(OCF1A);     // clear any pending interrupts;
      TIMSK1 |=  _BV(OCIE1A) ; // enable the output compare interrupt
      #if defined(WIRING)
        timerAttach(TIMER1OUTCOMPAREA_INT, Timer1Service);
      #endif
      }
  }

  static void finISR(timer16_Sequence_t timer) {
    #if defined WIRING   // Wiring
    if(timer == _timer1) {
      TIMSK &=  ~_BV(OCIE1A) ;  // disable timer 1 output compare interrupt
      timerDetach(TIMER1OUTCOMPAREA_INT);
    }
    else if(timer == _timer3) {
      ETIMSK &= ~_BV(OCIE3A);    // disable the timer3 output compare A interrupt
      timerDetach(TIMER3OUTCOMPAREA_INT);
    }
    #else
    //For arduino - in future: call here to a currently undefined function to reset the timer
    (void) timer;  // squash "unused parameter 'timer' [-Wunused-parameter]" warning
    #endif
  }
    
    static bool 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;
  }
  
  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) + 4 < usToTicks(REFRESH_INTERVAL) )  // 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
  #elif defined WIRING
    // Interrupt handlers for Wiring
    #if defined(_useTimer1)
    void Timer1Service()
    {
      handle_interrupts(_timer1, &TCNT1, &OCR1A);
    }
    #endif
  #endif

  inline int Servo::read() // return the value as degrees
  {
    return  map( this->readMicroseconds()+1, SERVO_MIN(), SERVO_MAX(), 0, 180);
  }


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 < 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::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;
  }

  inline bool Servo::attached() {
    return servos[this->servoIndex].Pin.isActive ;
  }



  

#endif