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Arduino-Development / libraries /Servo /src /avr /Servo.cpp
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Archive original Arduino development files (part 9)
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/*
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
*/
#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
#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