AccelStepper: AccelStepper library for Arduino (2023)

This is the Arduino AccelStepper library. It provides an object-oriented interface for 2, 3 or 4 pin stepper motors and motor drivers.

The standard Arduino IDE includes the Stepper library ( for stepper motors. It is perfectly adequate for simple, single motor applications.

(Video) Arduino - Homing Stepper Motors using the AccelStepper Library - Tutorial

AccelStepper significantly improves on the standard Arduino Stepper library in several ways:

  • Supports acceleration and deceleration
  • Supports multiple simultaneous steppers, with independent concurrent stepping on each stepper
  • Most API functions never delay() or block (unless otherwise stated)
  • Supports 2, 3 and 4 wire steppers, plus 3 and 4 wire half steppers.
  • Supports alternate stepping functions to enable support of AFMotor (
  • Supports stepper drivers such as the Sparkfun EasyDriver (based on 3967 driver chip)
  • Very slow speeds are supported
  • Extensive API
  • Subclass support

The latest version of this documentation can be downloaded from The version of the package that this documentation refers to can be downloaded from

Example Arduino programs are included to show the main modes of use.

(Video) Arduino with TB6600 using AccelStepper library

You can also find online help and discussion at 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

Beginners to C++ and stepper motors in general may find this helpful:

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 including Teensy 3.1 built using Arduino IDE 1.0.5 with teensyduino addon 1.18 and later.

(Video) Arduino with AccelStepper library and TB6600 stepper motor controller


Install in the usual way: unzip the distribution zip file to the libraries sub-folder of your sketchbook.


This code uses speed calculations as described in "Generate stepper-motor speed profiles in real time" by David Austin or or 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.

Adafruit Motor Shield V2

The included examples AFMotor_* are for Adafruit Motor Shield V1 and do not work with Adafruit Motor Shield V2. See for examples that work with Adafruit Motor Shield V2.

(Video) Updates for the AccelStepper library - TB6600 and Arduino


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 or here:


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.


This software is Copyright (C) 2010-2021 Mike McCauley. Use is subject to license conditions. The main licensing options available are GPL V3 or Commercial:

(Video) Homing with the AccelStepper library and a limit switch

Open Source Licensing GPL V3
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 23 when your application is distributed. See
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. To purchase a commercial license, contact
Revision History
1.0 Initial release
1.1 Added speed() function to get the current speed.
1.2 Added runSpeedToPosition() submitted by Gunnar Arndt.
1.3 Added support for stepper drivers (ie with Step and Direction inputs) with _pins == 1
1.4 Added functional contructor to support AFMotor, contributed by Limor, with example sketches.
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.
1.6 Fixed a problem with wrapping of microsecond stepping that could cause stepping to hang. Reported by Sandy Noble. Removed redundant _lastRunTime member.
1.7 Fixed a bug where setCurrentPosition() did not always work as expected. Reported by Peter Linhart.
1.8 Added support for 4 pin half-steppers, requested by Harvey Moon
1.9 setCurrentPosition() now also sets motor speed to 0.
1.10 Builds on Arduino 1.0
1.11 Improvments from Michael Ellison: Added optional enable line support for stepper drivers Added inversion for step/direction/enable lines for stepper drivers
1.12 Announce Google Group
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.
1.14 Fixed a problem with compiling under arduino 0021 reported by EmbeddedMan
1.15 Fixed a problem with runSpeedToPosition which did not correctly handle running backwards to a smaller target position. Added examples
1.16 Fixed some cases in the code where abs() was used instead of fabs().
1.17 Added example ProportionalControl
1.18 Fixed a problem: If one calls the funcion runSpeed() when Speed is zero, it makes steps without counting. reported by Friedrich, Klappenbach.
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.
1.20 Improved documentation and examples to show need for correctly specifying AccelStepper::FULL4WIRE and friends.
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
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.
1.23 Rewrite of the speed algorithms in line with Now expect smoother and more linear accelerations and decelerations. The desiredSpeed() function was removed.
1.24 Fixed a problem introduced in 1.23: with runToPosition, which did never returned
1.25 Now ignore attempts to set acceleration to 0.0
1.26 Fixed a problem where certina combinations of speed and accelration could cause oscillation about the target position.
1.27 Added stop() function to stop as fast as possible with current acceleration parameters. Also added new Quickstop example showing its use.
1.28 Fixed another problem where certain combinations of speed and acceleration 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.
1.29 Fixed a problem that could cause a DRIVER stepper to continually step with some sketches. Reported by Vadim.
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.
1.31 Updated author and distribution location details to
1.32 Fixed a problem with enableOutputs() and setEnablePin on Arduino Due that prevented the enable pin changing stae correctly. Reported by Duane Bishop.
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.
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.
1.35 Removed default args from setPinsInverted(bool, bool, bool, bool, bool) to prevent ambiguity with setPinsInverted(bool, bool, bool). Reported by Mac Mac.
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.
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.
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.
1.39 Updated typos in keywords.txt, courtesey Jon Magill.
1.40 Updated documentation, including testing on Teensy 3.1
1.41 Fixed an error in the acceleration calculations, resulting in acceleration of haldf the intended value
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.
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.
1.44 examples/DualMotorShield/DualMotorShield.ino examples/DualMotorShield/DualMotorShield.pde was missing from the distribution.
1.45 Fixed a problem where if setAcceleration was not called, there was no default acceleration. Reported by Michael Newman.
1.45 Fixed inaccuracy in acceleration rate by using Equation 15, suggested by Sebastian Gracki.
Performance improvements in runSpeed suggested by Jaakko Fagerlund.
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.
1.48 2015-08-25 Added new class MultiStepper that can manage multiple AccelSteppers, and cause them all to move to selected positions at such a (constant) speed that they all arrive at their target position at the same time. Suitable for X-Y flatbeds etc.
Added new method maxSpeed() to AccelStepper to return the currently configured maxSpeed.
1.49 2016-01-02 Testing with VID28 series instrument stepper motors and EasyDriver. OK, although with light pointers and slow speeds like 180 full steps per second the motor movement can be erratic, probably due to some mechanical resonance. Best to accelerate through this speed.
Added isRunning().
1.50 2016-02-25 AccelStepper::disableOutputs now sets the enable pion to OUTPUT mode if the enable pin is defined. Patch from Piet De Jong.
Added notes about the fact that AFMotor_* examples do not work with Adafruit Motor Shield V2.
1.51 2016-03-24 Fixed a problem reported by gregor: when resetting the stepper motor position using setCurrentPosition() the stepper speed is reset by setting _stepInterval to 0, but _speed is not reset. this results in the stepper motor not starting again when calling setSpeed() with the same speed the stepper was set to before.
1.52 2016-08-09 Added MultiStepper to keywords.txt. Improvements to efficiency of AccelStepper::runSpeed() as suggested by David Grayson. Improvements to speed accuracy as suggested by David Grayson.
1.53 2016-08-14 Backed out Improvements to speed accuracy from 1.52 as it did not work correctly.
1.54 2017-01-24 Fixed some warnings about unused arguments.
1.55 2017-01-25 Fixed another warning in MultiStepper.cpp
1.56 2017-02-03 Fixed minor documentation error with DIRECTION_CCW and DIRECTION_CW. Reported by David Mutterer. Added link to Binpress commercial license purchasing.
1.57 2017-03-28 _direction moved to protected at the request of Rudy Ercek. setMaxSpeed() and setAcceleration() now correct negative values to be positive.
1.58 2018-04-13 Add initialisation for _enableInverted in constructor.
1.59 2018-08-28 Update commercial licensing, remove binpress.
1.60 2020-03-07 Release under GPL V3
1.61 2020-04-20 Added yield() call in runToPosition(), so that platforms like esp8266 dont hang/crash during long runs.
1.62 2022-05-22 Added link to AccelStepper - The Missing Manual.
Fixed a problem when setting the maxSpeed to 1.0 due to incomplete initialisation. Reported by Olivier Pécheux.
1.63 2022-06-30 Added virtual destructor at the request of Jan.


How many steps is 28BYJ 48? ›

According to the data sheet, when the 28BYJ-48 motor is operated in full step mode each step corresponds to a rotation of 11.25°. This means there are 32 steps per revolution (360°/11.25° = 32).

What is Max speed of AccelStepper? ›

From AccelStepper documentation: 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.

What is AccelStepper library? ›

AccelStepper Library. The AccelStepper library allows you to connect multiple stepper motors with controlled acceleration and deceleration. Download: Included with the Teensyduino Installer.

What classes and functions are available in the Arduino stepper library? ›

  • Sustainability, Social Innovation.
  • Gaming.
  • Healthcare and Fitness.
  • AI.
  • Robotics.
  • Fashion and Wearables.
  • PRO / Industrial.
  • Agriculture and gardening.

How many stepper motors can an Arduino control? ›

If you would like to use stepper-drivers with STEP-/DIR-Input you need two IO-pins per stepper-motor. Depending on the maximum-stepfrequency you need you could use IO-pin-expanders to go up to 32, 64 or 128 stepper-drivers.

How does 28BYJ-48 Stepper Motor work? ›

28BYJ-48 stepper motor and ULN2003 Arduino (Quick tutorial for ...

How do I import an Arduino library? ›

Open the IDE and click to the "Sketch" menu and then Include Library > Manage Libraries. Then the Library Manager will open and you will find a list of libraries that are already installed or ready for installation.

What is stepper motor explain? ›

A stepper motor is a brushless, synchronous electric motor that converts digital pulses into mechanical shaft rotation. Its normal shaft motion consists of discrete angular movements of essentially uniform magnitude when driven from sequentially switched DC power supply.

What is set speed in Arduino? ›

Stepper - setSpeed()

This function sets the motor speed in rotations per minute (RPMs). This function doesn't make the motor turn, just sets the speed at which it will when you call step().

How do you control a stepper motor? ›

Fundamentally, the basic method of controlling a stepper motor is energizing and de-energizing the coils that surround the gear in the correct sequence. Varying the sequence and timing of the coil activations is how engineers customize the operation of a stepper motor to the needs of their applications.

How do you change the speed of a stepper motor? ›

There are two ways you can control the speed of your stepper motor. You can either decrease the delay time between each step or you can adjust the size of the step the motor takes. Decreasing the delay time is straightforward, just lower the delayMicroseconds and the stepper motor will have an increased step rate.

What is ULN2003 used for? ›

ULN2003 IC is one of the most commonly used Motor driver IC generally used when we need to drive high current loads using digital logic circuits like Op-maps, Timers, Gates, Arduino, PIC, ARM, etc.

What is pull in torque? ›

Definition of pull-in torque

: the maximum constant torque under which a motor will accelerate from rest to approximate normal speed.

What is idle in traction frequency? ›

"Idle In-traction Frequency" propably is maximum frequency at wich motor will start and "Idle Out-traction Frequency" propably is maximum speed of motor. "Idle" means without load. In your example start is guaranted below 600 steps/second and maximum speed is not less then 1000 steps/second.

Can a stepper motor run continuously? ›

Stepper motors can continue to rotate indefinitely, just as most motors will. If you use a properly designed controller and a stepper motor that's sized appropriately for the application, the motor can be left running.


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