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

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

#if defined(ARDUINO_ARCH_AVR)

#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

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

(void) timer; // squash "unused parameter 'timer' [-Wunused-parameter]" warning

#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 // ARDUINO_ARCH_AVR

Servo/src/avr/Servo.cpp at master · ArduinoLibrariesForks/Servo · GitHub

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