Here is a fixed version of the ServoTimer2 library that I corrected and tested using a Arduino Uno and one servo.
Note:
In my tests the servo positions were reversed from those in the standard servo.h library.
This can easily be compensated for using the map() function.
keywords.txt:
#######################################
# Syntax Coloring Map For Ultrasound
#######################################
#######################################
# Datatypes (KEYWORD1)
#######################################
ServoTimer2 KEYWORD1
#######################################
# Methods and Functions (KEYWORD2)
#######################################
attach KEYWORD2
detach KEYWORD2
write KEYWORD2
read KEYWORD2
attached KEYWORD2
#######################################
# Constants (LITERAL1)
#######################################ServoTimer2.h
/*
ServoTimer2.h - Interrupt driven Servo library for Arduino using
/*
This library uses Timer2 to drive up to 8 servos using interrupts so no refresh activity is required from within the sketch.
The usage and method naming is similar to the Arduino software servo library http://www.arduino.cc/playground/ComponentLib/Servo
except that pulse widths are in microseconds.
A servo is activated by creating an instance of the Servo class passing the desired pin to the attach() method.
The servo is pulsed in the background to the value most recently written using the write() method
Note that analogWrite of PWM on pins 3 and 11 is disabled when the first servo is attached
The methods are:
ServoTimer2 - 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 pulse width in microseconds.
read() - Gets the last written servo pulse width in microseconds.
attached() - Returns true if there is a servo attached.
detach() - Stops an attached servos from pulsing its i/o pin.
The library takes about 824 bytes of program memory and 32+(1*servos) bytes of SRAM.
The pulse width timing is accurate to within 1%
*/
// ensure this library description is only included once
#ifndef ServoTimer2_h
#define ServoTimer2_h
#include <inttypes.h>
typedef uint8_t boolean;
typedef uint8_t byte;
#define MIN_PULSE_WIDTH 610 // the shortest pulse sent to a servo
#define MAX_PULSE_WIDTH 2300 // the longest pulse sent to a servo
#define DEFAULT_PULSE_WIDTH 1500 // default pulse width when servo is attached
#define FRAME_SYNC_PERIOD 20000 // total frame duration in microseconds
#define NBR_CHANNELS 8 // the maximum number of channels, don't change this
typedef struct {
uint8_t nbr :5 ; // a pin number from 0 to 31
uint8_t isActive :1 ; // false if this channel not enabled, pin only pulsed if true
} ServoPin_t ;
typedef struct {
ServoPin_t Pin;
byte counter;
byte remainder;
} servo_t;
class ServoTimer2
{
public:
// constructor:
ServoTimer2();
uint8_t attach(int); // attach the given pin to the next free channel, sets pinMode, returns channel number or 0 if failure
// the attached servo is pulsed with the current pulse width value, (see the write method)
uint8_t attach(int, int, int); // as above but also sets min and max values for writes.
void detach();
void write(int); // store the pulse width in microseconds (between MIN_PULSE_WIDTH and MAX_PULSE_WIDTH)for this channel
int read(); // returns current pulse width in microseconds for this servo
boolean attached(); // return true if this servo is attached
private:
uint8_t chanIndex; // index into the channel data for this servo
};
// the following ServoArrayT2 class is not implemented in the first version of this library
class ServoArrayT2
{
public:
// constructor:
ServoArrayT2();
uint8_t attach(int); // attach the given pin to the next free channel, sets pinMode, returns channel number or 0 if failure
// channels are assigned consecutively starting from 1
// the attached servo is pulsed with the current pulse width value, (see the write method)
void detach(int); // detach the servo on the given channel
void write(int,int); // store the pulse width in microseconds (between MIN_PULSE_WIDTH and MAX_PULSE_WIDTH)for the given channel
int read(int); // returns current pulse width in microseconds for the given channel
boolean attached(int); // return true if the servo on the given channel is attached
private:
uint8_t chanIndex; // index into the channel data for this servo
};
#endifServoTimer2.cpp:
/* ServoTimer2.cpp*/
// AVR LibC Includes
#include <inttypes.h>
#include <avr/interrupt.h>
#include <Arduino.h>
#include "ServoTimer2.h"
static void initISR();
static void writeChan(uint8_t chan, int pulsewidth);
#define FRAME_SYNC_INDEX 0 // frame sync delay is the first entry in the channel array
#define FRAME_SYNC_PERIOD 20000 // total frame duration in microseconds
#define FRAME_SYNC_DELAY ((FRAME_SYNC_PERIOD - ( NBR_CHANNELS * DEFAULT_PULSE_WIDTH))/ 128) // number of iterations of the ISR to get the desired frame rate
#define DELAY_ADJUST 8 // number of microseconds of calculation overhead to be subtracted from pulse timings
static servo_t servos[NBR_CHANNELS+1]; // static array holding servo data for all channels
static volatile uint8_t Channel; // counter holding the channel being pulsed
static volatile uint8_t ISRCount; // iteration counter used in the interrupt routines;
uint8_t ChannelCount = 0; // counter holding the number of attached channels
static boolean isStarted = false; // flag to indicate if the ISR has been initialised
ISR (TIMER2_OVF_vect)
{
++ISRCount; // increment the overlflow counter
if (ISRCount == servos[Channel].counter ) // are we on the final iteration for this channel
{
TCNT2 = servos[Channel].remainder; // yes, set count for overflow after remainder ticks
}
else if(ISRCount > servos[Channel].counter)
{
// we have finished timing the channel so pulse it low and move on
if(servos[Channel].Pin.isActive == true) // check if activated
digitalWrite( servos[Channel].Pin.nbr,LOW); // pulse this channel low if active
Channel++; // increment to the next channel
ISRCount = 0; // reset the isr iteration counter
TCNT2 = 0; // reset the clock counter register
if( (Channel != FRAME_SYNC_INDEX) && (Channel <= NBR_CHANNELS) ){ // check if we need to pulse this channel
if(servos[Channel].Pin.isActive == true) // check if activated
digitalWrite( servos[Channel].Pin.nbr,HIGH); // its an active channel so pulse it high
}
else if(Channel > NBR_CHANNELS){
Channel = 0; // all done so start over
}
}
}
ServoTimer2::ServoTimer2()
{
if( ChannelCount < NBR_CHANNELS)
this->chanIndex = ++ChannelCount; // assign a channel number to this instance
else
this->chanIndex = 0; // todo // too many channels, assigning 0 inhibits this instance from functioning
}
uint8_t ServoTimer2::attach(int pin)
{
if( isStarted == false)
initISR();
if(this->chanIndex > 0)
{
//debug("attaching chan = ", chanIndex);
pinMode( pin, OUTPUT) ; // set servo pin to output
servos[this->chanIndex].Pin.nbr = pin;
servos[this->chanIndex].Pin.isActive = true;
}
return this->chanIndex ;
}
void ServoTimer2::detach()
{
servos[this->chanIndex].Pin.isActive = false;
}
void ServoTimer2::write(int pulsewidth)
{
writeChan(this->chanIndex, pulsewidth); // call the static function to store the data for this servo
}
int ServoTimer2::read()
{
unsigned int pulsewidth;
if( this->chanIndex > 0)
pulsewidth = servos[this->chanIndex].counter * 128 + ((255 - servos[this->chanIndex].remainder) / 2) + DELAY_ADJUST ;
else
pulsewidth = 0;
return pulsewidth;
}
boolean ServoTimer2::attached()
{
return servos[this->chanIndex].Pin.isActive ;
}
static void writeChan(uint8_t chan, int pulsewidth)
{
// calculate and store the values for the given channel
if( (chan > 0) && (chan <= NBR_CHANNELS) ) // ensure channel is valid
{
if( pulsewidth < MIN_PULSE_WIDTH ) // ensure pulse width is valid
pulsewidth = MIN_PULSE_WIDTH;
else if( pulsewidth > MAX_PULSE_WIDTH )
pulsewidth = MAX_PULSE_WIDTH;
pulsewidth -=DELAY_ADJUST; // subtract the time it takes to process the start and end pulses (mostly from digitalWrite)
servos[chan].counter = pulsewidth / 128;
servos[chan].remainder = 255 - (2 * (pulsewidth - ( servos[chan].counter * 128))); // the number of 0.5us ticks for timer overflow
}
}
static void initISR()
{
for(uint8_t i=1; i <= NBR_CHANNELS; i++) { // channels start from 1
writeChan(i, DEFAULT_PULSE_WIDTH); // store default values
}
servos[FRAME_SYNC_INDEX].counter = FRAME_SYNC_DELAY; // store the frame sync period
Channel = 0; // clear the channel index
ISRCount = 0; // clear the value of the ISR counter;
/* setup for timer 2 */
TIMSK2 = 0; // disable interrupts
TCCR2A = 0; // normal counting mode
TCCR2B = _BV(CS21); // set prescaler of 8
TCNT2 = 0; // clear the timer2 count
TIFR2 = _BV(TOV2); // clear pending interrupts;
TIMSK2 = _BV(TOIE2) ; // enable the overflow interrupt
isStarted = true; // flag to indicate this initialisation code has been executed
} ServoTimer2.pde [Example]:
// this sketch cycles three servos at different rates
#include <ServoTimer2.h> // the servo library
// define the pins for the servos
#define rollPin 2
#define pitchPin 3
#define yawPin 4
ServoTimer2 servoRoll; // declare variables for up to eight servos
ServoTimer2 servoPitch;
ServoTimer2 servoYaw;
void setup() {
servoRoll.attach(rollPin); // attach a pin to the servos and they will start pulsing
servoPitch.attach(pitchPin);
servoYaw.attach(yawPin);
}
// this function just increments a value until it reaches a maximum
int incPulse(int val, int inc){
if( val + inc > 2000 )
return 1000 ;
else
return val + inc;
}
void loop()
{
int val;
val = incPulse( servoRoll.read(), 1);
servoRoll.write(val);
val = incPulse( servoPitch.read(), 2);
servoPitch.write(val);
val = incPulse(servoYaw.read(), 4);
servoYaw.write(val);
delay(10);
}Enjoy!
.