Added #ifdef NUM_SERVOS to servo.cpp

Marlin/Servo.cpp

@@ -1,337 +1,339 @@
-/*
- 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) + 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
-
-#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 < 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 ;
-}
+/*
+ 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.
+
+*/
+#ifdef NUM_SERVOS
+#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) + 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
+
+#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 < 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 ;
+}
+
+#endif