请问这个库函数程序是怎么循环执行的？ -

#ifndef EasyStepper_h
#define EasyStepper_h
#include <stdlib.h>
#if ARDUINO >= 100
#include <Arduino.h>
#else
#include <WProgram.h>
#include <wiring.h>
#endif
/**
* author [email]shangcm@gmail.com[/email]
*/
class EasyStepper
{
public:
/**
* to create the EasyStepper
* parameters:
* stepPin the step pin
* directionPin the direction pin
* enablePin the enable pin
* directionPinsInverted if the value is true then invert HIGH/LOW value for direction pin
* enablePinsInverted if the value is true then invert HIGH/LOW value for enable pin
*/
EasyStepper(byte stepPin, byte directionPin, byte enablePin, bool directionPinsInverted, bool enablePinsInverted);
/**
* to startup the EasyStepper
*/
void startup();
/**
* to shutdown the EasyStepper, will release the enable pin to save power
*/
void shutdown();
/**
* to rotate steps from current position with speed, the acceleration = 0
* speed the speed for rotation, the unit is steps per second
* steps the steps to go
*/
void rotate(float speed, int steps);
/**
* to rotate steps from current position with speed
* speed the speed for rotation, the unit is steps per second
* steps the steps to go
* acceleration the acceleration, if it = 0, means no acceleration
*/
void rotate(float speed, int steps, int acceleration);
/**
* to stop the stepper, the motor will stay at current position
*/
void stop();
/**
* run, you must call this as frequently as possible, but at least once per minimum step interval,
* preferably in your main loop.
*/
void run();
/**
* if return true means the action is done
*/
boolean isDone();
/**
* enable the debug mode?
*/
void debugMode(boolean enabled);
protected:
//
private:
boolean debugModeFlag;
byte stepPin;
byte directionPin;
byte enablePin;
bool directionPinsInverted;
bool enablePinsInverted;
int acceleration;
int stage1; // the end step of the stage1
int stage2; // the end step of the stage2
int stepsToGo;
int stepsGone;
float stepTime;
float startTime;
float stage1StepTime;
float stage3StepTime;
unsigned long nextTimestamp;
boolean done;
void step();
};
#endif

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#include "EasyStepper.h"
EasyStepper::EasyStepper(byte stepPin, byte directionPin, byte enablePin, bool directionPinsInverted, bool enablePinsInverted)
{
// save the parameters
this->stepPin = stepPin;
this->directionPin = directionPin;
this->enablePin = enablePin;
this->directionPinsInverted = directionPinsInverted;
this->enablePinsInverted = enablePinsInverted;
}
void EasyStepper::startup()
{
// set the pin mode
pinMode(this->stepPin, OUTPUT);
pinMode(this->directionPin, OUTPUT);
pinMode(this->enablePin, OUTPUT);
// enable the stepper
digitalWrite(enablePin, HIGH ^ this->enablePinsInverted);
// initialize the done to true
this->done = true;
}
void EasyStepper::shutdown()
{
// disable the stepper
digitalWrite(enablePin, LOW ^ this->enablePinsInverted);
}
void EasyStepper::debugMode(boolean enabled)
{
this->debugModeFlag = enabled;
}
void EasyStepper::rotate(float speed, int steps)
{
this->rotate(speed, steps, 0);
}
void EasyStepper::rotate(float speed, int steps, int acceleration)
{
// ignore the zero value
if (speed != 0 && steps != 0)
{
if (steps > 0)
{
// CW
digitalWrite(directionPin, HIGH ^ this->directionPinsInverted);
}
else if (steps < 0)
{
// CCW
digitalWrite(directionPin, LOW ^ this->directionPinsInverted);
}
// done flag
this->done = false;
// the steps to go
this->stepsToGo = abs(steps);
// the acceleration
this->acceleration = abs(acceleration);
if (this->stepsToGo <= 4)
{
this->acceleration = 0;
}
// change the speed to stepTime, micro seconds per step
this->stepTime = 1000.0 * 1000.0 / abs(speed);
// start time
this->startTime = this->stepTime * (this->acceleration + 1);
// stage1
this->stage1 = this->stepsToGo / 4;
this->stage1StepTime = (float) this->acceleration * this->stepTime / this->stage1;
// stage2
this->stage2 = this->stepsToGo / 4 * 3;
this->stage3StepTime = (float) this->acceleration * this->stepTime / (this->stepsToGo - this->stage2);
// the steps gone
this->stepsGone = 0;
// current timestamp
unsigned long time = micros();
if (this->debugModeFlag)
{
Serial.print("rotate: direction=");
Serial.print(steps > 0 ? "CW" : "CCW");
Serial.print(", stepsToGo=");
Serial.print(this->stepsToGo);
Serial.print(", acceleration=");
Serial.print(this->acceleration);
Serial.print(", startTime=");
Serial.print(this->startTime);
Serial.print(", stage1=");
Serial.print(this->stage1);
Serial.print(", stage1StepTime=");
Serial.print(this->stage1StepTime);
Serial.print(", stage2=");
Serial.print(this->stage2);
Serial.print(", stage3StepTime=");
Serial.print(this->stage3StepTime);
Serial.print(", stepTime=");
Serial.print(this->stepTime);
Serial.print(", currentTimestamp=");
Serial.println(time);
}
// call the step method to rotate the motor
this->step();
}
}
void EasyStepper::stop()
{
this->stepsToGo = 0;
this->done = true;
}
void EasyStepper::run()
{
// the current timestamp
unsigned long time = micros();
if (!this->done && time >= this->nextTimestamp)
{
this->step();
}
if (this->debugModeFlag)
{
Serial.print("currentTimeStamp=");
Serial.println(time);
}
}
void EasyStepper::step()
{
// are there some steps to rotate?
if (this->stepsToGo > this->stepsGone)
{
// HIGH value
digitalWrite(stepPin, HIGH);
// delay
delayMicroseconds(2);
// LOW value
digitalWrite(stepPin, LOW);
// increase the stepsGone
this->stepsGone++;
// default: stage2
float nextStepTime = this->stepTime;
if (this->acceleration != 0)
{
if (this->stepsGone < this->stage1)
{
// stage1: down to stepTime from startTime
nextStepTime = this->startTime - this->stage1StepTime * this->stepsGone;
}
else if (this->stepsGone >= this->stage2)
{
// stage3: up to startTime from stepTime
nextStepTime = this->stepTime + this->stage3StepTime * (this->stepsGone - this->stage2 + 1);
}
}
// current timestamp
unsigned long time = micros();
this->nextTimestamp = time + nextStepTime;
if (this->debugModeFlag)
{
Serial.print("step: stepsGone=");
Serial.print(this->stepsGone);
Serial.print(", currentTimestamp=");
Serial.print(time);
Serial.print(", nextTimestamp=");
Serial.print(this->nextTimestamp);
Serial.print(", nextStepTime=");
Serial.println(nextStepTime);
}
}
else
{
this->done = true;
}
}
boolean EasyStepper::isDone()
{
return this->done;
}

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