MTR CTRL

Dependencies:   mbed

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API Documentation at this revision

Comitter:
yweng36
Date:
Thu Feb 25 18:42:43 2016 +0000
Commit message:
MTR CTRL

Changed in this revision

AccelStepper.cpp Show annotated file Show diff for this revision Revisions of this file
AccelStepper.h Show annotated file Show diff for this revision Revisions of this file
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diff -r 000000000000 -r a0391774b0e5 AccelStepper.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/AccelStepper.cpp	Thu Feb 25 18:42:43 2016 +0000
@@ -0,0 +1,651 @@
+// AccelStepper.cpp
+//
+// Copyright (C) 2009-2013 Mike McCauley
+// $Id: AccelStepper.cpp,v 1.19 2014/10/31 06:05:27 mikem Exp mikem $
+
+#include "AccelStepper.h"
+
+#if 0
+// Some debugging assistance
+void dump(uint8_t* p, int l)
+{
+    int i;
+
+    for (i = 0; i < l; i++)
+    {
+	Serial.print(p[i], HEX);
+	Serial.print(" ");
+    }
+    Serial.println("");
+}
+#endif
+
+void AccelStepper::moveTo(long absolute)
+{
+    if (_targetPos != absolute)
+    {
+	_targetPos = absolute;
+	computeNewSpeed();
+	// compute new n?
+    }
+}
+
+void AccelStepper::move(long relative)
+{
+    moveTo(_currentPos + relative);
+}
+
+// Implements steps according to the current step interval
+// You must call this at least once per step
+// returns true if a step occurred
+bool AccelStepper::runSpeed()
+{
+	extern Timer t;
+    // Dont do anything unless we actually have a step interval
+    if (!_stepInterval)
+	return false;
+
+    //unsigned long time = micros();
+	unsigned long time = t.read_us();
+    unsigned long nextStepTime = _lastStepTime + _stepInterval;
+    // Gymnastics to detect wrapping of either the nextStepTime and/or the current time
+    if (   ((nextStepTime >= _lastStepTime) && ((time >= nextStepTime) || (time < _lastStepTime)))
+	|| ((nextStepTime < _lastStepTime) && ((time >= nextStepTime) && (time < _lastStepTime))))
+    {
+	if (_direction == DIRECTION_CW)
+	{
+	    // Clockwise
+	    _currentPos += 1;
+	}
+	else
+	{
+	    // Anticlockwise  
+	    _currentPos -= 1;
+	}
+	step(_currentPos);
+
+	_lastStepTime = time;
+	return true;
+    }
+    else
+    {
+	return false;
+    }
+}
+
+long AccelStepper::distanceToGo()
+{
+    return _targetPos - _currentPos;
+}
+
+long AccelStepper::targetPosition()
+{
+    return _targetPos;
+}
+
+long AccelStepper::currentPosition()
+{
+    return _currentPos;
+}
+
+// Useful during initialisations or after initial positioning
+// Sets speed to 0
+void AccelStepper::setCurrentPosition(long position)
+{
+    _targetPos = _currentPos = position;
+    _n = 0;
+    _stepInterval = 0;
+}
+
+void AccelStepper::computeNewSpeed()
+{
+    long distanceTo = distanceToGo(); // +ve is clockwise from curent location
+
+    long stepsToStop = (long)((_speed * _speed) / (2.0 * _acceleration)); // Equation 16
+
+    if (distanceTo == 0 && stepsToStop <= 1)
+    {
+	// We are at the target and its time to stop
+	_stepInterval = 0;
+	_speed = 0.0;
+	_n = 0;
+	return;
+    }
+
+    if (distanceTo > 0)
+    {
+	// We are anticlockwise from the target
+	// Need to go clockwise from here, maybe decelerate now
+	if (_n > 0)
+	{
+	    // Currently accelerating, need to decel now? Or maybe going the wrong way?
+	    if ((stepsToStop >= distanceTo) || _direction == DIRECTION_CCW)
+		_n = -stepsToStop; // Start deceleration
+	}
+	else if (_n < 0)
+	{
+	    // Currently decelerating, need to accel again?
+	    if ((stepsToStop < distanceTo) && _direction == DIRECTION_CW)
+		_n = -_n; // Start accceleration
+	}
+    }
+    else if (distanceTo < 0)
+    {
+	// We are clockwise from the target
+	// Need to go anticlockwise from here, maybe decelerate
+	if (_n > 0)
+	{
+	    // Currently accelerating, need to decel now? Or maybe going the wrong way?
+	    if ((stepsToStop >= -distanceTo) || _direction == DIRECTION_CW)
+		_n = -stepsToStop; // Start deceleration
+	}
+	else if (_n < 0)
+	{
+	    // Currently decelerating, need to accel again?
+	    if ((stepsToStop < -distanceTo) && _direction == DIRECTION_CCW)
+		_n = -_n; // Start accceleration
+	}
+    }
+
+    // Need to accelerate or decelerate
+    if (_n == 0)
+    {
+	// First step from stopped
+	_cn = _c0;
+	_direction = (distanceTo > 0) ? DIRECTION_CW : DIRECTION_CCW;
+    }
+    else
+    {
+	// Subsequent step. Works for accel (n is +_ve) and decel (n is -ve).
+	_cn = _cn - ((2.0 * _cn) / ((4.0 * _n) + 1)); // Equation 13
+	_cn = max(_cn, _cmin); 
+    }
+    _n++;
+    _stepInterval = _cn;
+    _speed = 1000000.0 / _cn;
+    if (_direction == DIRECTION_CCW)
+	_speed = -_speed;
+
+#if 0
+    Serial.println(_speed);
+    Serial.println(_acceleration);
+    Serial.println(_cn);
+    Serial.println(_c0);
+    Serial.println(_n);
+    Serial.println(_stepInterval);
+    Serial.println(distanceTo);
+    Serial.println(stepsToStop);
+    Serial.println("-----");
+#endif
+}
+
+// Run the motor to implement speed and acceleration in order to proceed to the target position
+// You must call this at least once per step, preferably in your main loop
+// If the motor is in the desired position, the cost is very small
+// returns true if the motor is still running to the target position.
+bool AccelStepper::run()
+{
+    if (runSpeed())
+	  computeNewSpeed();
+    return _speed != 0.0 || distanceToGo() != 0;
+}
+
+AccelStepper::AccelStepper(uint8_t interface, PinName pin1, PinName pin2, PinName pin3, PinName pin4, bool enable)
+{
+    _interface = interface;
+    _currentPos = 0;
+    _targetPos = 0;
+    _speed = 0.0;
+    _maxSpeed = 1.0;
+    _acceleration = 0.0;
+    _sqrt_twoa = 1.0;
+    _stepInterval = 0;
+    _minPulseWidth = 1;
+    _lastStepTime = 0;
+	// _pin[0] = pin1;
+	// _pin[1] = pin2;
+	// _pin[2] = pin3;
+	// _pin[3] = pin4;
+    _pin0 = new DigitalOut(pin1);
+    _pin1 = new DigitalOut(pin2);
+    _pin2 = new DigitalOut(pin3);
+    _pin3 = new DigitalOut(pin4);
+
+    // NEW
+    _n = 0;
+    _c0 = 0.0;
+    _cn = 0.0;
+    _cmin = 1.0;
+    _direction = DIRECTION_CCW;
+
+    int i;
+    for (i = 0; i < 4; i++)
+	_pinInverted[i] = 0;
+    if (enable)
+	enableOutputs();
+    // Some reasonable default
+    setAcceleration(1);
+}
+
+AccelStepper::AccelStepper(void (*forward)(), void (*backward)())
+{
+    _interface = 0;
+    _currentPos = 0;
+    _targetPos = 0;
+    _speed = 0.0;
+    _maxSpeed = 1.0;
+    _acceleration = 0.0;
+    _sqrt_twoa = 1.0;
+    _stepInterval = 0;
+    _minPulseWidth = 1;
+    _lastStepTime = 0;
+    _forward = forward;
+    _backward = backward;
+
+    // NEW
+    _n = 0;
+    _c0 = 0.0;
+    _cn = 0.0;
+    _cmin = 1.0;
+    _direction = DIRECTION_CCW;
+
+    int i;
+    for (i = 0; i < 4; i++)
+	_pinInverted[i] = 0;
+    // Some reasonable default
+    setAcceleration(1);
+}
+
+void AccelStepper::setMaxSpeed(float speed)
+{
+    if (_maxSpeed != speed)
+    {
+	_maxSpeed = speed;
+	_cmin = 1000000.0 / speed;
+	// Recompute _n from current speed and adjust speed if accelerating or cruising
+	if (_n > 0)
+	{
+	    _n = (long)((_speed * _speed) / (2.0 * _acceleration)); // Equation 16
+	    computeNewSpeed();
+	}
+    }
+}
+
+void AccelStepper::setAcceleration(float acceleration)
+{
+    if (acceleration == 0.0)
+	return;
+    if (_acceleration != acceleration)
+    {
+	// Recompute _n per Equation 17
+	_n = _n * (_acceleration / acceleration);
+	// New c0 per Equation 7, with correction per Equation 15
+	_c0 = 0.676 * sqrt(2.0 / acceleration) * 1000000.0; // Equation 15
+	_acceleration = acceleration;
+	computeNewSpeed();
+    }
+}
+
+void AccelStepper::setSpeed(float speed)
+{
+    if (speed == _speed)
+        return;
+    speed = constrain(speed, -_maxSpeed, _maxSpeed);
+    if (speed == 0.0)
+	_stepInterval = 0;
+    else
+    {
+	_stepInterval = fabs(1000000.0 / speed);
+	_direction = (speed > 0.0) ? DIRECTION_CW : DIRECTION_CCW;
+    }
+    _speed = speed;
+}
+
+float AccelStepper::speed()
+{
+    return _speed;
+}
+
+// Subclasses can override
+void AccelStepper::step(long step)
+{
+    switch (_interface)
+    {
+        case FUNCTION:
+            step0(step);
+            break;
+
+	case DRIVER:
+	    step1(step);
+	    break;
+    
+	case FULL2WIRE:
+	    step2(step);
+	    break;
+    
+	case FULL3WIRE:
+	    step3(step);
+	    break;  
+
+	case FULL4WIRE:
+	    step4(step);
+	    break;  
+
+	case HALF3WIRE:
+	    step6(step);
+	    break;  
+		
+	case HALF4WIRE:
+	    step8(step);
+	    break;  
+    }
+}
+
+// You might want to override this to implement eg serial output
+// bit 0 of the mask corresponds to _pin[0]
+// bit 1 of the mask corresponds to _pin[1]
+// ....
+void AccelStepper::setOutputPins(uint8_t mask)
+{
+//    uint8_t numpins = 2;
+//    if (_interface == FULL4WIRE || _interface == HALF4WIRE)
+//        numpins = 4;
+//    else if (_interface == FULL3WIRE || _interface == HALF3WIRE)
+//        numpins = 3;
+//    uint8_t i;
+//    for (i = 0; i < numpins; i++)
+//        digitalWrite(_pin[i], (mask & (1 << i)) ? (HIGH ^ _pinInverted[i]) : (LOW ^ _pinInverted[i]));
+	*_pin0 = (mask & (1 << 0)) ? (HIGH ^ _pinInverted[0]) : (LOW ^ _pinInverted[0]);
+	*_pin1 = (mask & (1 << 1)) ? (HIGH ^ _pinInverted[1]) : (LOW ^ _pinInverted[1]);
+    if (_interface == FULL4WIRE || _interface == HALF4WIRE) {
+		*_pin2 = (mask & (1 << 2)) ? (HIGH ^ _pinInverted[2]) : (LOW ^ _pinInverted[2]);
+		*_pin3 = (mask & (1 << 3)) ? (HIGH ^ _pinInverted[3]) : (LOW ^ _pinInverted[3]);
+	}
+    else if (_interface == FULL3WIRE || _interface == HALF3WIRE)
+		*_pin2 = (mask & (1 << 2)) ? (HIGH ^ _pinInverted[2]) : (LOW ^ _pinInverted[2]);
+}
+
+// 0 pin step function (ie for functional usage)
+void AccelStepper::step0(long step)
+{
+  if (_speed > 0)
+    _forward();
+  else
+    _backward();
+}
+
+// 1 pin step function (ie for stepper drivers)
+// This is passed the current step number (0 to 7)
+// Subclasses can override
+void AccelStepper::step1(long step)
+{
+    // _pin[0] is step, _pin[1] is direction
+    setOutputPins(_direction ? 0b10 : 0b00); // Set direction first else get rogue pulses
+    setOutputPins(_direction ? 0b11 : 0b01); // step HIGH
+    // Caution 200ns setup time 
+    // Delay the minimum allowed pulse width
+    //delayMicroseconds(_minPulseWidth);
+    wait_us(_minPulseWidth);
+    setOutputPins(_direction ? 0b10 : 0b00); // step LOW
+
+}
+
+
+// 2 pin step function
+// This is passed the current step number (0 to 7)
+// Subclasses can override
+void AccelStepper::step2(long step)
+{
+    switch (step & 0x3)
+    {
+	case 0: /* 01 */
+	    setOutputPins(0b10);
+	    break;
+
+	case 1: /* 11 */
+	    setOutputPins(0b11);
+	    break;
+
+	case 2: /* 10 */
+	    setOutputPins(0b01);
+	    break;
+
+	case 3: /* 00 */
+	    setOutputPins(0b00);
+	    break;
+    }
+}
+// 3 pin step function
+// This is passed the current step number (0 to 7)
+// Subclasses can override
+void AccelStepper::step3(long step)
+{
+    switch (step % 3)
+    {
+	case 0:    // 100
+	    setOutputPins(0b100);
+	    break;
+
+	case 1:    // 001
+	    setOutputPins(0b001);
+	    break;
+
+	case 2:    //010
+	    setOutputPins(0b010);
+	    break;
+	    
+    }
+}
+
+// 4 pin step function for half stepper
+// This is passed the current step number (0 to 7)
+// Subclasses can override
+void AccelStepper::step4(long step)
+{
+    switch (step & 0x3)
+    {
+	case 0:    // 1010
+	    setOutputPins(0b0101);
+	    break;
+
+	case 1:    // 0110
+	    setOutputPins(0b0110);
+	    break;
+
+	case 2:    //0101
+	    setOutputPins(0b1010);
+	    break;
+
+	case 3:    //1001
+	    setOutputPins(0b1001);
+	    break;
+    }
+}
+
+// 3 pin half step function
+// This is passed the current step number (0 to 7)
+// Subclasses can override
+void AccelStepper::step6(long step)
+{
+    switch (step % 6)
+    {
+	case 0:    // 100
+	    setOutputPins(0b100);
+            break;
+	    
+        case 1:    // 101
+	    setOutputPins(0b101);
+            break;
+	    
+	case 2:    // 001
+	    setOutputPins(0b001);
+            break;
+	    
+        case 3:    // 011
+	    setOutputPins(0b011);
+            break;
+	    
+	case 4:    // 010
+	    setOutputPins(0b010);
+            break;
+	    
+	case 5:    // 011
+	    setOutputPins(0b110);
+            break;
+	    
+    }
+}
+
+// 4 pin half step function
+// This is passed the current step number (0 to 7)
+// Subclasses can override
+void AccelStepper::step8(long step)
+{
+    switch (step & 0x7)
+    {
+	case 0:    // 1000
+	    setOutputPins(0b0001);
+            break;
+	    
+        case 1:    // 1010
+	    setOutputPins(0b0101);
+            break;
+	    
+	case 2:    // 0010
+	    setOutputPins(0b0100);
+            break;
+	    
+        case 3:    // 0110
+	    setOutputPins(0b0110);
+            break;
+	    
+	case 4:    // 0100
+	    setOutputPins(0b0010);
+            break;
+	    
+        case 5:    //0101
+	    setOutputPins(0b1010);
+            break;
+	    
+	case 6:    // 0001
+	    setOutputPins(0b1000);
+            break;
+	    
+        case 7:    //1001
+	    setOutputPins(0b1001);
+            break;
+    }
+}
+    
+// Prevents power consumption on the outputs
+void    AccelStepper::disableOutputs()
+{   
+    if (! _interface) return;
+
+    setOutputPins(0); // Handles inversion automatically
+	// if (_enablePin != 0xff)
+    if (_enablePin)
+        // digitalWrite(_enablePin, LOW ^ _enableInverted);
+        *_enablePin = LOW ^ _enableInverted;
+}
+
+void    AccelStepper::enableOutputs()
+{
+    if (! _interface) 
+	return;
+
+    //pinMode(_pin[0], OUTPUT);
+    //pinMode(_pin[1], OUTPUT);
+    if (_interface == FULL4WIRE || _interface == HALF4WIRE)
+    {
+        //pinMode(_pin[2], OUTPUT);
+        //pinMode(_pin[3], OUTPUT);
+    }
+    else if (_interface == FULL3WIRE || _interface == HALF3WIRE)
+    {
+        //pinMode(_pin[2], OUTPUT);
+    }
+
+    // if (_enablePin != 0xff)
+	if (_enablePin)
+    {
+        //pinMode(_enablePin, OUTPUT);
+        //digitalWrite(_enablePin, HIGH ^ _enableInverted);
+        *_enablePin = HIGH ^ _enableInverted;
+    }
+}
+
+void AccelStepper::setMinPulseWidth(unsigned int minWidth)
+{
+    _minPulseWidth = minWidth;
+}
+
+// void AccelStepper::setEnablePin(uint8_t enablePin)
+void AccelStepper::setEnablePin(PinName enablePin)
+{
+    // _enablePin = enablePin;
+	_enablePin = new DigitalOut(enablePin);
+
+    // This happens after construction, so init pin now.
+	// if (_enablePin != 0xff)
+    if (*_enablePin)
+    {
+        //pinMode(_enablePin, OUTPUT);
+        //digitalWrite(_enablePin, HIGH ^ _enableInverted);
+        *_enablePin = HIGH ^ _enableInverted;
+    }
+}
+
+void AccelStepper::setPinsInverted(bool directionInvert, bool stepInvert, bool enableInvert)
+{
+    _pinInverted[0] = stepInvert;
+    _pinInverted[1] = directionInvert;
+    _enableInverted = enableInvert;
+}
+
+void AccelStepper::setPinsInverted(bool pin1Invert, bool pin2Invert, bool pin3Invert, bool pin4Invert, bool enableInvert)
+{    
+    _pinInverted[0] = pin1Invert;
+    _pinInverted[1] = pin2Invert;
+    _pinInverted[2] = pin3Invert;
+    _pinInverted[3] = pin4Invert;
+    _enableInverted = enableInvert;
+}
+
+// Blocks until the target position is reached and stopped
+void AccelStepper::runToPosition()
+{
+    while (run())
+	;
+}
+
+bool AccelStepper::runSpeedToPosition()
+{
+    if (_targetPos == _currentPos)
+	return false;
+    if (_targetPos >_currentPos)
+	_direction = DIRECTION_CW;
+    else
+	_direction = DIRECTION_CCW;
+    return runSpeed();
+}
+
+// Blocks until the new target position is reached
+void AccelStepper::runToNewPosition(long position)
+{
+    moveTo(position);
+    runToPosition();
+}
+
+void AccelStepper::stop()
+{
+    if (_speed != 0.0)
+    {    
+	long stepsToStop = (long)((_speed * _speed) / (2.0 * _acceleration)) + 1; // Equation 16 (+integer rounding)
+	if (_speed > 0)
+	    move(stepsToStop);
+	else
+	    move(-stepsToStop);
+    }
+}
+
diff -r 000000000000 -r a0391774b0e5 AccelStepper.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/AccelStepper.h	Thu Feb 25 18:42:43 2016 +0000
@@ -0,0 +1,680 @@
+// AccelStepper.h
+//
+/// \mainpage AccelStepper library for MBED
+///
+/// This is the MBED AccelStepper library.
+/// It provides an object-oriented interface for 2, 3 or 4 pin stepper motors.
+/// Based on the Arduino AccelStepper library by Airspayce.com
+/// Translated for MBED by Jaap Vermaas <jaap@tuxic.nl>, 03-2015
+///
+/// The standard Arduino IDE includes the Stepper library
+/// (http://arduino.cc/en/Reference/Stepper) for stepper motors. It is
+/// perfectly adequate for simple, single motor applications.
+///
+/// AccelStepper significantly improves on the standard Arduino Stepper library in several ways:
+/// \li Supports acceleration and deceleration
+/// \li Supports multiple simultaneous steppers, with independent concurrent stepping on each stepper
+/// \li API functions never delay() or block
+/// \li Supports 2, 3 and 4 wire steppers, plus 3 and 4 wire half steppers.
+/// \li Supports alternate stepping functions to enable support of AFMotor (https://github.com/adafruit/Adafruit-Motor-Shield-library)
+/// \li Supports stepper drivers such as the Sparkfun EasyDriver (based on 3967 driver chip)
+/// \li Very slow speeds are supported
+/// \li Extensive API
+/// \li Subclass support
+///
+/// The latest version of this documentation can be downloaded from 
+/// http://www.airspayce.com/mikem/arduino/AccelStepper
+/// The version of the package that this documentation refers to can be downloaded 
+/// from http://www.airspayce.com/mikem/arduino/AccelStepper/AccelStepper-1.47.zip
+///
+/// Example Arduino programs are included to show the main modes of use.
+///
+/// You can also find online help and discussion at http://groups.google.com/group/accelstepper
+/// Please use that group for all questions and discussions on this topic. 
+/// Do not contact the author directly, unless it is to discuss commercial licensing.
+/// Before asking a question or reporting a bug, please read http://www.catb.org/esr/faqs/smart-questions.html
+///
+/// Tested on Arduino Diecimila and Mega with arduino-0018 & arduino-0021 
+/// on OpenSuSE 11.1 and avr-libc-1.6.1-1.15,
+/// cross-avr-binutils-2.19-9.1, cross-avr-gcc-4.1.3_20080612-26.5.
+/// Tested on Teensy http://www.pjrc.com/teensy including Teensy 3.1 built using Arduino IDE 1.0.5 with 
+/// teensyduino addon 1.18 and later.
+///
+/// \par Installation
+///
+/// Install in the usual way: unzip the distribution zip file to the libraries
+/// sub-folder of your sketchbook. 
+///
+/// \par Theory
+///
+/// This code uses speed calculations as described in 
+/// "Generate stepper-motor speed profiles in real time" by David Austin 
+/// http://fab.cba.mit.edu/classes/MIT/961.09/projects/i0/Stepper_Motor_Speed_Profile.pdf
+/// with the exception that AccelStepper uses steps per second rather than radians per second
+/// (because we dont know the step angle of the motor)
+/// An initial step interval is calculated for the first step, based on the desired acceleration
+/// On subsequent steps, shorter step intervals are calculated based 
+/// on the previous step until max speed is achieved.
+/// 
+/// \par Donations
+///
+/// This library is offered under a free GPL license for those who want to use it that way. 
+/// We try hard to keep it up to date, fix bugs
+/// and to provide free support. If this library has helped you save time or money, please consider donating at
+/// http://www.airspayce.com or here:
+///
+/// \htmlonly <form action="https://www.paypal.com/cgi-bin/webscr" method="post"><input type="hidden" name="cmd" value="_donations" /> <input type="hidden" name="business" value="mikem@airspayce.com" /> <input type="hidden" name="lc" value="AU" /> <input type="hidden" name="item_name" value="Airspayce" /> <input type="hidden" name="item_number" value="AccelStepper" /> <input type="hidden" name="currency_code" value="USD" /> <input type="hidden" name="bn" value="PP-DonationsBF:btn_donateCC_LG.gif:NonHosted" /> <input type="image" alt="PayPal — The safer, easier way to pay online." name="submit" src="https://www.paypalobjects.com/en_AU/i/btn/btn_donateCC_LG.gif" /> <img alt="" src="https://www.paypalobjects.com/en_AU/i/scr/pixel.gif" width="1" height="1" border="0" /></form> \endhtmlonly
+/// 
+/// \par Trademarks
+///
+/// AccelStepper is a trademark of AirSpayce Pty Ltd. The AccelStepper mark was first used on April 26 2010 for
+/// international trade, and is used only in relation to motor control hardware and software.
+/// It is not to be confused with any other similar marks covering other goods and services.
+///
+/// \par Copyright
+///
+/// This software is Copyright (C) 2010 Mike McCauley. Use is subject to license
+/// conditions. The main licensing options available are GPL V2 or Commercial:
+///
+/// \par Open Source Licensing GPL V2
+/// This is the appropriate option if you want to share the source code of your
+/// application with everyone you distribute it to, and you also want to give them
+/// the right to share who uses it. If you wish to use this software under Open
+/// Source Licensing, you must contribute all your source code to the open source
+/// community in accordance with the GPL Version 2 when your application is
+/// distributed. See http://www.gnu.org/copyleft/gpl.html
+/// 
+/// \par Commercial Licensing
+/// This is the appropriate option if you are creating proprietary applications
+/// and you are not prepared to distribute and share the source code of your
+/// application. Contact info@airspayce.com for details.
+///
+/// \par Revision History
+/// \version 1.0 Initial release
+///
+/// \version 1.1 Added speed() function to get the current speed.
+/// \version 1.2 Added runSpeedToPosition() submitted by Gunnar Arndt.
+/// \version 1.3 Added support for stepper drivers (ie with Step and Direction inputs) with _pins == 1
+/// \version 1.4 Added functional contructor to support AFMotor, contributed by Limor, with example sketches.
+/// \version 1.5 Improvements contributed by Peter Mousley: Use of microsecond steps and other speed improvements
+///              to increase max stepping speed to about 4kHz. New option for user to set the min allowed pulse width.
+///              Added checks for already running at max speed and skip further calcs if so. 
+/// \version 1.6 Fixed a problem with wrapping of microsecond stepping that could cause stepping to hang. 
+///              Reported by Sandy Noble.
+///              Removed redundant _lastRunTime member.
+/// \version 1.7 Fixed a bug where setCurrentPosition() did not always work as expected. 
+///              Reported by Peter Linhart.
+/// \version 1.8 Added support for 4 pin half-steppers, requested by Harvey Moon
+/// \version 1.9 setCurrentPosition() now also sets motor speed to 0.
+/// \version 1.10 Builds on Arduino 1.0
+/// \version 1.11 Improvments from Michael Ellison:
+///   Added optional enable line support for stepper drivers
+///   Added inversion for step/direction/enable lines for stepper drivers
+/// \version 1.12 Announce Google Group
+/// \version 1.13 Improvements to speed calculation. Cost of calculation is now less in the worst case, 
+///    and more or less constant in all cases. This should result in slightly beter high speed performance, and
+///    reduce anomalous speed glitches when other steppers are accelerating. 
+///    However, its hard to see how to replace the sqrt() required at the very first step from 0 speed.
+/// \version 1.14 Fixed a problem with compiling under arduino 0021 reported by EmbeddedMan
+/// \version 1.15 Fixed a problem with runSpeedToPosition which did not correctly handle
+///    running backwards to a smaller target position. Added examples
+/// \version 1.16 Fixed some cases in the code where abs() was used instead of fabs().
+/// \version 1.17 Added example ProportionalControl
+/// \version 1.18 Fixed a problem: If one calls the funcion runSpeed() when Speed is zero, it makes steps 
+///    without counting. reported by  Friedrich, Klappenbach.
+/// \version 1.19 Added MotorInterfaceType and symbolic names for the number of pins to use
+///               for the motor interface. Updated examples to suit.
+///               Replaced individual pin assignment variables _pin1, _pin2 etc with array _pin[4].
+///               _pins member changed to _interface.
+///               Added _pinInverted array to simplify pin inversion operations.
+///               Added new function setOutputPins() which sets the motor output pins.
+///               It can be overridden in order to provide, say, serial output instead of parallel output
+///               Some refactoring and code size reduction.
+/// \version 1.20 Improved documentation and examples to show need for correctly
+///               specifying AccelStepper::FULL4WIRE and friends.
+/// \version 1.21 Fixed a problem where desiredSpeed could compute the wrong step acceleration
+///               when _speed was small but non-zero. Reported by Brian Schmalz.
+///               Precompute sqrt_twoa to improve performance and max possible stepping speed
+/// \version 1.22 Added Bounce.pde example
+///               Fixed a problem where calling moveTo(), setMaxSpeed(), setAcceleration() more 
+///               frequently than the step time, even
+///               with the same values, would interfere with speed calcs. Now a new speed is computed 
+///               only if there was a change in the set value. Reported by Brian Schmalz.
+/// \version 1.23 Rewrite of the speed algorithms in line with 
+///               http://fab.cba.mit.edu/classes/MIT/961.09/projects/i0/Stepper_Motor_Speed_Profile.pdf
+///               Now expect smoother and more linear accelerations and decelerations. The desiredSpeed()
+///               function was removed.
+/// \version 1.24  Fixed a problem introduced in 1.23: with runToPosition, which did never returned
+/// \version 1.25  Now ignore attempts to set acceleration to 0.0
+/// \version 1.26  Fixed a problem where certina combinations of speed and accelration could cause
+///                oscillation about the target position.
+/// \version 1.27  Added stop() function to stop as fast as possible with current acceleration parameters.
+///                Also added new Quickstop example showing its use.
+/// \version 1.28  Fixed another problem where certain combinations of speed and accelration could cause
+///                oscillation about the target position.
+///                Added support for 3 wire full and half steppers such as Hard Disk Drive spindle.
+///                Contributed by Yuri Ivatchkovitch.
+/// \version 1.29  Fixed a problem that could cause a DRIVER stepper to continually step
+///                with some sketches. Reported by Vadim.
+/// \version 1.30  Fixed a problem that could cause stepper to back up a few steps at the end of
+///                accelerated travel with certain speeds. Reported and patched by jolo.
+/// \version 1.31  Updated author and distribution location details to airspayce.com
+/// \version 1.32  Fixed a problem with enableOutputs() and setEnablePin on Arduino Due that
+///                prevented the enable pin changing stae correctly. Reported by Duane Bishop.
+/// \version 1.33  Fixed an error in example AFMotor_ConstantSpeed.pde did not setMaxSpeed();
+///                Fixed a problem that caused incorrect pin sequencing of FULL3WIRE and HALF3WIRE.
+///                Unfortunately this meant changing the signature for all step*() functions.
+///                Added example MotorShield, showing how to use AdaFruit Motor Shield to control
+///                a 3 phase motor such as a HDD spindle motor (and without using the AFMotor library.
+/// \version 1.34  Added setPinsInverted(bool pin1Invert, bool pin2Invert, bool pin3Invert, bool pin4Invert, bool enableInvert) 
+///                to allow inversion of 2, 3 and 4 wire stepper pins. Requested by Oleg.
+/// \version 1.35  Removed default args from setPinsInverted(bool, bool, bool, bool, bool) to prevent ambiguity with 
+///                setPinsInverted(bool, bool, bool). Reported by Mac Mac.
+/// \version 1.36  Changed enableOutputs() and disableOutputs() to be virtual so can be overridden.
+///                Added new optional argument 'enable' to constructor, which allows you toi disable the 
+///                automatic enabling of outputs at construction time. Suggested by Guido.
+/// \version 1.37  Fixed a problem with step1 that could cause a rogue step in the 
+///                wrong direction (or not,
+///                depending on the setup-time requirements of the connected hardware). 
+///                Reported by Mark Tillotson.
+/// \version 1.38  run() function incorrectly always returned true. Updated function and doc so it returns true 
+///                if the motor is still running to the target position.
+/// \version 1.39  Updated typos in keywords.txt, courtesey Jon Magill.
+/// \version 1.40  Updated documentation, including testing on Teensy 3.1
+/// \version 1.41  Fixed an error in the acceleration calculations, resulting in acceleration of haldf the intended value
+/// \version 1.42  Improved support for FULL3WIRE and HALF3WIRE output pins. These changes were in Yuri's original
+///                contribution but did not make it into production.<br>
+/// \version 1.43  Added DualMotorShield example. Shows how to use AccelStepper to control 2 x 2 phase steppers using the 
+///                Itead Studio Arduino Dual Stepper Motor Driver Shield model IM120417015.<br>
+/// \version 1.44  examples/DualMotorShield/DualMotorShield.ino examples/DualMotorShield/DualMotorShield.pde
+///                was missing from the distribution.<br>
+/// \version 1.45  Fixed a problem where if setAcceleration was not called, there was no default
+///                acceleration. Reported by Michael Newman.<br>
+/// \version 1.45  Fixed inaccuracy in acceleration rate by using Equation 15, suggested by Sebastian Gracki.<br>
+///                Performance improvements in runSpeed suggested by Jaakko Fagerlund.<br>
+/// \version 1.46  Fixed error in documentation for runToPosition().
+///                Reinstated time calculations in runSpeed() since new version is reported 
+///                not to work correctly under some circumstances. Reported by Oleg V Gavva.<br>
+
+///
+/// \author  Mike McCauley (mikem@airspayce.com) DO NOT CONTACT THE AUTHOR DIRECTLY: USE THE LISTS
+// Copyright (C) 2009-2013 Mike McCauley
+// $Id: AccelStepper.h,v 1.21 2014/10/31 06:05:30 mikem Exp mikem $
+
+#ifndef AccelStepper_h
+#define AccelStepper_h
+
+#include <stdlib.h>
+#include <mbed.h>
+#define max(a,b) (((a) > (b)) ? (a) : (b))
+#define constrain(amt,low,high) ((amt)<(low)?(low):((amt)>(high)?(high):(amt)))
+#define LOW false
+#define HIGH true
+//#if ARDUINO >= 100
+//#include <Arduino.h>
+//#else
+//#include <WProgram.h>
+//#include <wiring.h>
+//#endif
+
+// These defs cause trouble on some versions of Arduino
+#undef round
+
+/////////////////////////////////////////////////////////////////////
+/// \class AccelStepper AccelStepper.h <AccelStepper.h>
+/// \brief Support for stepper motors with acceleration etc.
+///
+/// This defines a single 2 or 4 pin stepper motor, or stepper moter with fdriver chip, with optional
+/// acceleration, deceleration, absolute positioning commands etc. Multiple
+/// simultaneous steppers are supported, all moving 
+/// at different speeds and accelerations. 
+///
+/// \par Operation
+/// This module operates by computing a step time in microseconds. The step
+/// time is recomputed after each step and after speed and acceleration
+/// parameters are changed by the caller. The time of each step is recorded in
+/// microseconds. The run() function steps the motor once if a new step is due.
+/// The run() function must be called frequently until the motor is in the
+/// desired position, after which time run() will do nothing.
+///
+/// \par Positioning
+/// Positions are specified by a signed long integer. At
+/// construction time, the current position of the motor is consider to be 0. Positive
+/// positions are clockwise from the initial position; negative positions are
+/// anticlockwise. The current position can be altered for instance after
+/// initialization positioning.
+///
+/// \par Caveats
+/// This is an open loop controller: If the motor stalls or is oversped,
+/// AccelStepper will not have a correct 
+/// idea of where the motor really is (since there is no feedback of the motor's
+/// real position. We only know where we _think_ it is, relative to the
+/// initial starting point).
+///
+/// \par Performance
+/// The fastest motor speed that can be reliably supported is about 4000 steps per
+/// second at a clock frequency of 16 MHz on Arduino such as Uno etc. 
+/// Faster processors can support faster stepping speeds. 
+/// However, any speed less than that
+/// down to very slow speeds (much less than one per second) are also supported,
+/// provided the run() function is called frequently enough to step the motor
+/// whenever required for the speed set.
+/// Calling setAcceleration() is expensive,
+/// since it requires a square root to be calculated.
+class AccelStepper
+{
+public:
+    /// \brief Symbolic names for number of pins.
+    /// Use this in the pins argument the AccelStepper constructor to 
+    /// provide a symbolic name for the number of pins
+    /// to use.
+    typedef enum
+    {
+	FUNCTION  = 0, ///< Use the functional interface, implementing your own driver functions (internal use only)
+	DRIVER    = 1, ///< Stepper Driver, 2 driver pins required
+	FULL2WIRE = 2, ///< 2 wire stepper, 2 motor pins required
+	FULL3WIRE = 3, ///< 3 wire stepper, such as HDD spindle, 3 motor pins required
+        FULL4WIRE = 4, ///< 4 wire full stepper, 4 motor pins required
+	HALF3WIRE = 6, ///< 3 wire half stepper, such as HDD spindle, 3 motor pins required
+	HALF4WIRE = 8  ///< 4 wire half stepper, 4 motor pins required
+    } MotorInterfaceType;
+
+    /// Constructor. You can have multiple simultaneous steppers, all moving
+    /// at different speeds and accelerations, provided you call their run()
+    /// functions at frequent enough intervals. Current Position is set to 0, target
+    /// position is set to 0. MaxSpeed and Acceleration default to 1.0.
+    /// The motor pins will be initialised to OUTPUT mode during the
+    /// constructor by a call to enableOutputs().
+    /// \param[in] interface Number of pins to interface to. 1, 2, 4 or 8 are
+    /// supported, but it is preferred to use the \ref MotorInterfaceType symbolic names. 
+    /// AccelStepper::DRIVER (1) means a stepper driver (with Step and Direction pins).
+    /// If an enable line is also needed, call setEnablePin() after construction.
+    /// You may also invert the pins using setPinsInverted().
+    /// AccelStepper::FULL2WIRE (2) means a 2 wire stepper (2 pins required). 
+    /// AccelStepper::FULL3WIRE (3) means a 3 wire stepper, such as HDD spindle (3 pins required). 
+    /// AccelStepper::FULL4WIRE (4) means a 4 wire stepper (4 pins required). 
+    /// AccelStepper::HALF3WIRE (6) means a 3 wire half stepper, such as HDD spindle (3 pins required)
+    /// AccelStepper::HALF4WIRE (8) means a 4 wire half stepper (4 pins required)
+    /// Defaults to AccelStepper::FULL4WIRE (4) pins.
+    /// \param[in] pin1 Arduino digital pin number for motor pin 1. Defaults
+    /// to pin 2. For a AccelStepper::DRIVER (interface==1), 
+    /// this is the Step input to the driver. Low to high transition means to step)
+    /// \param[in] pin2 Arduino digital pin number for motor pin 2. Defaults
+    /// to pin 3. For a AccelStepper::DRIVER (interface==1), 
+    /// this is the Direction input the driver. High means forward.
+    /// \param[in] pin3 Arduino digital pin number for motor pin 3. Defaults
+    /// to pin 4.
+    /// \param[in] pin4 Arduino digital pin number for motor pin 4. Defaults
+    /// to pin 5.
+    /// \param[in] enable If this is true (the default), enableOutputs() will be called to enable
+    /// the output pins at construction time.
+    // AccelStepper(uint8_t interface = AccelStepper::FULL4WIRE, uint8_t pin1 = 2, uint8_t pin2 = 3, uint8_t pin3 = 4, uint8_t pin4 = 5, bool enable = true);
+	AccelStepper(uint8_t interface, PinName pin1 = LED1, PinName pin2 = LED2, PinName pin3 = LED3, PinName pin4 = LED4, bool enable = true);
+
+    /// Alternate Constructor which will call your own functions for forward and backward steps. 
+    /// You can have multiple simultaneous steppers, all moving
+    /// at different speeds and accelerations, provided you call their run()
+    /// functions at frequent enough intervals. Current Position is set to 0, target
+    /// position is set to 0. MaxSpeed and Acceleration default to 1.0.
+    /// Any motor initialization should happen before hand, no pins are used or initialized.
+    /// \param[in] forward void-returning procedure that will make a forward step
+    /// \param[in] backward void-returning procedure that will make a backward step
+    AccelStepper(void (*forward)(), void (*backward)());
+    
+    /// Set the target position. The run() function will try to move the motor (at most one step per call)
+    /// from the current position to the target position set by the most
+    /// recent call to this function. Caution: moveTo() also recalculates the speed for the next step. 
+    /// If you are trying to use constant speed movements, you should call setSpeed() after calling moveTo().
+    /// \param[in] absolute The desired absolute position. Negative is
+    /// anticlockwise from the 0 position.
+    void    moveTo(long absolute); 
+
+    /// Set the target position relative to the current position
+    /// \param[in] relative The desired position relative to the current position. Negative is
+    /// anticlockwise from the current position.
+    void    move(long relative);
+
+    /// Poll the motor and step it if a step is due, implementing
+    /// accelerations and decelerations to acheive the target position. You must call this as
+    /// frequently as possible, but at least once per minimum step time interval,
+    /// preferably in your main loop. Note that each call to run() will make at most one step, and then only when a step is due,
+    /// based on the current speed and the time since the last step.
+    /// \return true if the motor is still running to the target position.
+    bool run();
+
+    /// Poll the motor and step it if a step is due, implementing a constant
+    /// speed as set by the most recent call to setSpeed(). You must call this as
+    /// frequently as possible, but at least once per step interval,
+    /// \return true if the motor was stepped.
+    bool runSpeed();
+
+    /// Sets the maximum permitted speed. The run() function will accelerate
+    /// up to the speed set by this function.
+    /// Caution: the maximum speed achievable depends on your processor and clock speed.
+    /// \param[in] speed The desired maximum speed in steps per second. Must
+    /// be > 0. Caution: Speeds that exceed the maximum speed supported by the processor may
+    /// Result in non-linear accelerations and decelerations.
+    void    setMaxSpeed(float speed);
+
+    /// Sets the acceleration/deceleration rate.
+    /// \param[in] acceleration The desired acceleration in steps per second
+    /// per second. Must be > 0.0. This is an expensive call since it requires a square 
+    /// root to be calculated. Dont call more ofthen than needed
+    void    setAcceleration(float acceleration);
+
+    /// Sets the desired constant speed for use with runSpeed().
+    /// \param[in] speed The desired constant speed in steps per
+    /// second. Positive is clockwise. Speeds of more than 1000 steps per
+    /// second are unreliable. Very slow speeds may be set (eg 0.00027777 for
+    /// once per hour, approximately. Speed accuracy depends on the Arduino
+    /// crystal. Jitter depends on how frequently you call the runSpeed() function.
+    void    setSpeed(float speed);
+
+    /// The most recently set speed
+    /// \return the most recent speed in steps per second
+    float   speed();
+
+    /// The distance from the current position to the target position.
+    /// \return the distance from the current position to the target position
+    /// in steps. Positive is clockwise from the current position.
+    long    distanceToGo();
+
+    /// The most recently set target position.
+    /// \return the target position
+    /// in steps. Positive is clockwise from the 0 position.
+    long    targetPosition();
+
+    /// The currently motor position.
+    /// \return the current motor position
+    /// in steps. Positive is clockwise from the 0 position.
+    long    currentPosition();  
+
+    /// Resets the current position of the motor, so that wherever the motor
+    /// happens to be right now is considered to be the new 0 position. Useful
+    /// for setting a zero position on a stepper after an initial hardware
+    /// positioning move.
+    /// Has the side effect of setting the current motor speed to 0.
+    /// \param[in] position The position in steps of wherever the motor
+    /// happens to be right now.
+    void    setCurrentPosition(long position);  
+    
+    /// Moves the motor (with acceleration/deceleration) 
+    /// to the target position and blocks until it is at
+    /// position. Dont use this in event loops, since it blocks.
+    void    runToPosition();
+
+    /// Runs at the currently selected speed until the target position is reached
+    /// Does not implement accelerations.
+    /// \return true if it stepped
+    bool runSpeedToPosition();
+
+    /// Moves the motor (with acceleration/deceleration)
+    /// to the new target position and blocks until it is at
+    /// position. Dont use this in event loops, since it blocks.
+    /// \param[in] position The new target position.
+    void    runToNewPosition(long position);
+
+    /// Sets a new target position that causes the stepper
+    /// to stop as quickly as possible, using the current speed and acceleration parameters.
+    void stop();
+
+    /// Disable motor pin outputs by setting them all LOW
+    /// Depending on the design of your electronics this may turn off
+    /// the power to the motor coils, saving power.
+    /// This is useful to support Arduino low power modes: disable the outputs
+    /// during sleep and then reenable with enableOutputs() before stepping
+    /// again.
+    virtual void    disableOutputs();
+
+    /// Enable motor pin outputs by setting the motor pins to OUTPUT
+    /// mode. Called automatically by the constructor.
+    virtual void    enableOutputs();
+
+    /// Sets the minimum pulse width allowed by the stepper driver. The minimum practical pulse width is 
+    /// approximately 20 microseconds. Times less than 20 microseconds
+    /// will usually result in 20 microseconds or so.
+    /// \param[in] minWidth The minimum pulse width in microseconds. 
+    void    setMinPulseWidth(unsigned int minWidth);
+
+    /// Sets the enable pin number for stepper drivers.
+    /// 0xFF indicates unused (default).
+    /// Otherwise, if a pin is set, the pin will be turned on when 
+    /// enableOutputs() is called and switched off when disableOutputs() 
+    /// is called.
+    /// \param[in] enablePin Arduino digital pin number for motor enable
+    /// \sa setPinsInverted
+    void    setEnablePin(PinName enablePin);
+
+    /// Sets the inversion for stepper driver pins
+    /// \param[in] directionInvert True for inverted direction pin, false for non-inverted
+    /// \param[in] stepInvert      True for inverted step pin, false for non-inverted
+    /// \param[in] enableInvert    True for inverted enable pin, false (default) for non-inverted
+    void    setPinsInverted(bool directionInvert = false, bool stepInvert = false, bool enableInvert = false);
+
+    /// Sets the inversion for 2, 3 and 4 wire stepper pins
+    /// \param[in] pin1Invert True for inverted pin1, false for non-inverted
+    /// \param[in] pin2Invert True for inverted pin2, false for non-inverted
+    /// \param[in] pin3Invert True for inverted pin3, false for non-inverted
+    /// \param[in] pin4Invert True for inverted pin4, false for non-inverted
+    /// \param[in] enableInvert    True for inverted enable pin, false (default) for non-inverted
+    void    setPinsInverted(bool pin1Invert, bool pin2Invert, bool pin3Invert, bool pin4Invert, bool enableInvert);
+
+protected:
+	DigitalOut *_pin0;
+	DigitalOut *_pin1;
+	DigitalOut *_pin2;
+	DigitalOut *_pin3;
+
+    /// \brief Direction indicator
+    /// Symbolic names for the direction the motor is turning
+    typedef enum
+    {
+	DIRECTION_CCW = 0,  ///< Clockwise
+        DIRECTION_CW  = 1   ///< Counter-Clockwise
+    } Direction;
+
+    /// Forces the library to compute a new instantaneous speed and set that as
+    /// the current speed. It is called by
+    /// the library:
+    /// \li  after each step
+    /// \li  after change to maxSpeed through setMaxSpeed()
+    /// \li  after change to acceleration through setAcceleration()
+    /// \li  after change to target position (relative or absolute) through
+    /// move() or moveTo()
+    void           computeNewSpeed();
+
+    /// Low level function to set the motor output pins
+    /// bit 0 of the mask corresponds to _pin[0]
+    /// bit 1 of the mask corresponds to _pin[1]
+    /// You can override this to impment, for example serial chip output insted of using the
+    /// output pins directly
+    virtual void   setOutputPins(uint8_t mask);
+
+    /// Called to execute a step. Only called when a new step is
+    /// required. Subclasses may override to implement new stepping
+    /// interfaces. The default calls step1(), step2(), step4() or step8() depending on the
+    /// number of pins defined for the stepper.
+    /// \param[in] step The current step phase number (0 to 7)
+    virtual void   step(long step);
+
+    /// Called to execute a step using stepper functions (pins = 0) Only called when a new step is
+    /// required. Calls _forward() or _backward() to perform the step
+    /// \param[in] step The current step phase number (0 to 7)
+    virtual void   step0(long step);
+
+    /// Called to execute a step on a stepper driver (ie where pins == 1). Only called when a new step is
+    /// required. Subclasses may override to implement new stepping
+    /// interfaces. The default sets or clears the outputs of Step pin1 to step, 
+    /// and sets the output of _pin2 to the desired direction. The Step pin (_pin1) is pulsed for 1 microsecond
+    /// which is the minimum STEP pulse width for the 3967 driver.
+    /// \param[in] step The current step phase number (0 to 7)
+    virtual void   step1(long step);
+
+    /// Called to execute a step on a 2 pin motor. Only called when a new step is
+    /// required. Subclasses may override to implement new stepping
+    /// interfaces. The default sets or clears the outputs of pin1 and pin2
+    /// \param[in] step The current step phase number (0 to 7)
+    virtual void   step2(long step);
+
+    /// Called to execute a step on a 3 pin motor, such as HDD spindle. Only called when a new step is
+    /// required. Subclasses may override to implement new stepping
+    /// interfaces. The default sets or clears the outputs of pin1, pin2,
+    /// pin3
+    /// \param[in] step The current step phase number (0 to 7)
+    virtual void   step3(long step);
+
+    /// Called to execute a step on a 4 pin motor. Only called when a new step is
+    /// required. Subclasses may override to implement new stepping
+    /// interfaces. The default sets or clears the outputs of pin1, pin2,
+    /// pin3, pin4.
+    /// \param[in] step The current step phase number (0 to 7)
+    virtual void   step4(long step);
+
+    /// Called to execute a step on a 3 pin motor, such as HDD spindle. Only called when a new step is
+    /// required. Subclasses may override to implement new stepping
+    /// interfaces. The default sets or clears the outputs of pin1, pin2,
+    /// pin3
+    /// \param[in] step The current step phase number (0 to 7)
+    virtual void   step6(long step);
+
+    /// Called to execute a step on a 4 pin half-steper motor. Only called when a new step is
+    /// required. Subclasses may override to implement new stepping
+    /// interfaces. The default sets or clears the outputs of pin1, pin2,
+    /// pin3, pin4.
+    /// \param[in] step The current step phase number (0 to 7)
+    virtual void   step8(long step);
+
+private:
+    /// Number of pins on the stepper motor. Permits 2 or 4. 2 pins is a
+    /// bipolar, and 4 pins is a unipolar.
+    uint8_t        _interface;          // 0, 1, 2, 4, 8, See MotorInterfaceType
+
+    /// Arduino pin number assignments for the 2 or 4 pins required to interface to the
+    /// stepper motor or driver
+    uint8_t        _pin[4];
+
+    /// Whether the _pins is inverted or not
+    uint8_t        _pinInverted[4];
+
+    /// The current absolution position in steps.
+    long           _currentPos;    // Steps
+
+    /// The target position in steps. The AccelStepper library will move the
+    /// motor from the _currentPos to the _targetPos, taking into account the
+    /// max speed, acceleration and deceleration
+    long           _targetPos;     // Steps
+
+    /// The current motos speed in steps per second
+    /// Positive is clockwise
+    float          _speed;         // Steps per second
+
+    /// The maximum permitted speed in steps per second. Must be > 0.
+    float          _maxSpeed;
+
+    /// The acceleration to use to accelerate or decelerate the motor in steps
+    /// per second per second. Must be > 0
+    float          _acceleration;
+    float          _sqrt_twoa; // Precomputed sqrt(2*_acceleration)
+
+    /// The current interval between steps in microseconds.
+    /// 0 means the motor is currently stopped with _speed == 0
+    unsigned long  _stepInterval;
+
+    /// The last step time in microseconds
+    unsigned long  _lastStepTime;
+
+    /// The minimum allowed pulse width in microseconds
+    unsigned int   _minPulseWidth;
+
+    /// Is the direction pin inverted?
+    ///bool           _dirInverted; /// Moved to _pinInverted[1]
+
+    /// Is the step pin inverted?
+    ///bool           _stepInverted; /// Moved to _pinInverted[0]
+
+    /// Is the enable pin inverted?
+    bool           _enableInverted;
+
+    /// Enable pin for stepper driver, or 0xFF if unused.
+    //uint8_t        _enablePin;
+	DigitalOut *_enablePin;
+
+    /// The pointer to a forward-step procedure
+    void (*_forward)();
+
+    /// The pointer to a backward-step procedure
+    void (*_backward)();
+
+    /// The step counter for speed calculations
+    long _n;
+
+    /// Initial step size in microseconds
+    float _c0;
+
+    /// Last step size in microseconds
+    float _cn;
+
+    /// Min step size in microseconds based on maxSpeed
+    float _cmin; // at max speed
+
+    /// Current direction motor is spinning in
+    bool _direction; // 1 == CW
+
+};
+
+/// @example Random.pde
+/// Make a single stepper perform random changes in speed, position and acceleration
+
+/// @example Overshoot.pde
+///  Check overshoot handling
+/// which sets a new target position and then waits until the stepper has 
+/// achieved it. This is used for testing the handling of overshoots
+
+/// @example MultiStepper.pde
+/// Shows how to multiple simultaneous steppers
+/// Runs one stepper forwards and backwards, accelerating and decelerating
+/// at the limits. Runs other steppers at the same time
+
+/// @example ConstantSpeed.pde
+/// Shows how to run AccelStepper in the simplest,
+/// fixed speed mode with no accelerations
+
+/// @example Blocking.pde 
+/// Shows how to use the blocking call runToNewPosition
+/// Which sets a new target position and then waits until the stepper has 
+/// achieved it.
+
+/// @example AFMotor_MultiStepper.pde
+/// Control both Stepper motors at the same time with different speeds
+/// and accelerations. 
+
+/// @example AFMotor_ConstantSpeed.pde
+/// Shows how to run AccelStepper in the simplest,
+/// fixed speed mode with no accelerations
+
+/// @example ProportionalControl.pde
+/// Make a single stepper follow the analog value read from a pot or whatever
+/// The stepper will move at a constant speed to each newly set posiiton, 
+/// depending on the value of the pot.
+
+/// @example Bounce.pde
+/// Make a single stepper bounce from one limit to another, observing
+/// accelrations at each end of travel
+
+/// @example Quickstop.pde
+/// Check stop handling.
+/// Calls stop() while the stepper is travelling at full speed, causing
+/// the stepper to stop as quickly as possible, within the constraints of the
+/// current acceleration.
+
+/// @example MotorShield.pde
+/// Shows how to use AccelStepper to control a 3-phase motor, such as a HDD spindle motor
+/// using the Adafruit Motor Shield http://www.ladyada.net/make/mshield/index.html.
+
+/// @example DualMotorShield.pde
+/// Shows how to use AccelStepper to control 2 x 2 phase steppers using the 
+/// Itead Studio Arduino Dual Stepper Motor Driver Shield
+/// model IM120417015
+
+#endif 
+
diff -r 000000000000 -r a0391774b0e5 main.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Thu Feb 25 18:42:43 2016 +0000
@@ -0,0 +1,33 @@
+/*
+  sample program for AccelStepper.h
+  inspired by the Bounce example of the Arduino version
+
+
+*/
+#include "AccelStepper.h"
+
+/**
+*** Main function
+**/
+
+AccelStepper stepper(4, p21, p22, p23, p24); 
+
+Timer t;
+
+int main() 
+{
+  t.start();
+  stepper.setMaxSpeed(200);
+  stepper.setAcceleration(50);
+  stepper.moveTo(500);
+  stepper.setMinPulseWidth(50);
+
+
+
+  while (true) {
+  	if (stepper.distanceToGo() == 0)
+		stepper.moveTo(-stepper.currentPosition());
+	stepper.run();
+  }
+}
+
diff -r 000000000000 -r a0391774b0e5 mbed.bld
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Thu Feb 25 18:42:43 2016 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/f141b2784e32
\ No newline at end of file