uln200xa: Initial implementation

This driver was tested on a Grove Geared Stepper with Driver, the
uln2003a paired with a 28BYJ-48 unipolar stepper motor.

Signed-off-by: Jon Trulson <jtrulson@ics.com>
Signed-off-by: John Van Drasek <john.r.van.drasek@intel.com>

examples/c++/CMakeLists.txt

@@ -111,6 +111,7 @@ add_executable (waterlevel-example waterlevel.cxx)
 add_executable (tm1637-example tm1637.cxx)
 add_executable (zfm20-example zfm20.cxx)
 add_executable (zfm20-register-example zfm20-register.cxx)
+add_executable (uln200xa-example uln200xa.cxx)
 
 include_directories (${PROJECT_SOURCE_DIR}/src/hmc5883l)
 include_directories (${PROJECT_SOURCE_DIR}/src/grove)
@@ -200,6 +201,7 @@ include_directories (${PROJECT_SOURCE_DIR}/src/apds9002)
 include_directories (${PROJECT_SOURCE_DIR}/src/waterlevel)
 include_directories (${PROJECT_SOURCE_DIR}/src/tm1637)
 include_directories (${PROJECT_SOURCE_DIR}/src/zfm20)
+include_directories (${PROJECT_SOURCE_DIR}/src/uln200xa)
 
 target_link_libraries (hmc5883l-example hmc5883l ${CMAKE_THREAD_LIBS_INIT})
 target_link_libraries (groveled-example grove ${CMAKE_THREAD_LIBS_INIT})
@@ -312,3 +314,4 @@ target_link_libraries (waterlevel-example waterlevel ${CMAKE_THREAD_LIBS_INIT})
 target_link_libraries (tm1637-example tm1637 ${CMAKE_THREAD_LIBS_INIT})
 target_link_libraries (zfm20-example zfm20 ${CMAKE_THREAD_LIBS_INIT})
 target_link_libraries (zfm20-register-example zfm20 ${CMAKE_THREAD_LIBS_INIT})
+target_link_libraries (uln200xa-example uln200xa ${CMAKE_THREAD_LIBS_INIT})

examples/c++/uln200xa.cxx

@@ -0,0 +1,62 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2015 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <unistd.h>
+#include <iostream>
+#include "uln200xa.h"
+
+using namespace std;
+
+int main ()
+{
+  //! [Interesting]
+
+  // Instantiate a Stepper motor on a ULN200XA Dual H-Bridge.
+
+  // This was tested with the Grove Gear Stepper Motor with Driver
+
+  // Wire the pins so that I1 is pin D8, I2 is pin D9, I3 is pin D10 and
+  // I4 is pin D11
+  upm::ULN200XA* uln200xa = new upm::ULN200XA(4096, 8, 9, 10, 11);
+
+  uln200xa->setSpeed(5);
+  uln200xa->setDirection(upm::ULN200XA::DIR_CW);
+  cout << "Rotating 1 revolution clockwise." << endl;
+  uln200xa->stepperSteps(4096);
+  cout << "Sleeping for 2 seconds..." << endl;
+  sleep(2);
+  cout << "Rotating 1/2 revolution counter clockwise." << endl;
+  uln200xa->setDirection(upm::ULN200XA::DIR_CCW);
+  uln200xa->stepperSteps(2048);
+
+  // turn off the power
+  uln200xa->release();
+
+  //! [Interesting]
+  cout << "Exiting..." << endl;
+
+  delete uln200xa;
+  return 0;
+}
+

examples/javascript/uln200xa.js

@@ -0,0 +1,71 @@
+/*jslint node:true, vars:true, bitwise:true, unparam:true */
+/*jshint unused:true */
+/*
+* Author:  Jon Trulson <jtrulson@ics.com>
+* Copyright (c) 2015 Intel Corporation.
+*
+* Permission is hereby granted, free of charge, to any person obtaining
+* a copy of this software and associated documentation files (the
+* "Software"), to deal in the Software without restriction, including
+* without limitation the rights to use, copy, modify, merge, publish,
+* distribute, sublicense, and/or sell copies of the Software, and to
+* permit persons to whom the Software is furnished to do so, subject to
+* the following conditions:
+*
+* The above copyright notice and this permission notice shall be
+* included in all copies or substantial portions of the Software.
+*
+* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+var Uln200xa_lib = require('jsupm_uln200xa');
+
+// Instantiate a Stepper motor on a ULN200XA Darlington Motor Driver
+// This was tested with the Grove Geared Step Motor with Driver
+
+// Instantiate a ULN2003XA stepper object
+var myUln200xa_obj = new Uln200xa_lib.ULN200XA(4096, 8, 9, 10, 11);
+
+myUln200xa_obj.goForward = function()
+{
+    myUln200xa_obj.setSpeed(5); // 5 RPMs
+    myUln200xa_obj.setDirection(Uln200xa_lib.ULN200XA.DIR_CW);
+    console.log("Rotating 1 revolution clockwise.");
+    myUln200xa_obj.stepperSteps(4096);
+};
+
+myUln200xa_obj.reverseDirection = function()
+{
+	console.log("Rotating 1/2 revolution counter clockwise.");
+	myUln200xa_obj.setDirection(Uln200xa_lib.ULN200XA.DIR_CCW);
+	myUln200xa_obj.stepperSteps(2048);
+};
+
+myUln200xa_obj.stop = function()
+{
+	myUln200xa_obj.release();
+};
+
+myUln200xa_obj.quit = function()
+{
+	myUln200xa_obj = null;
+	Uln200xa_lib.cleanUp();
+	Uln200xa_lib = null;
+	console.log("Exiting");
+	process.exit(0);
+};
+
+// Run ULN200xa driven stepper
+myUln200xa_obj.goForward();
+setTimeout(myUln200xa_obj.reverseDirection, 2000);
+setTimeout(function()
+{
+	myUln200xa_obj.stop();
+	myUln200xa_obj.quit();
+}, 2000);

examples/python/uln200xa.py

@@ -0,0 +1,66 @@
+#!/usr/bin/python
+# Author:  Jon Trulson <jtrulson@ics.com>
+# Copyright (c) 2015 Intel Corporation.
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be
+# included in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+
+import time, sys, signal, atexit
+import pyupm_uln200xa as upmULN200XA
+
+# Instantiate a Stepper motor on a ULN200XA Darlington Motor Driver
+# This was tested with the Grove Geared Step Motor with Driver
+
+# Instantiate a ULN2003XA stepper object
+myUln200xa = upmULN200XA.ULN200XA(4096, 8, 9, 10, 11)
+
+## Exit handlers ##
+# This stops python from printing a stacktrace when you hit control-C
+def SIGINTHandler(signum, frame):
+	raise SystemExit
+
+# This lets you run code on exit,
+# including functions from myUln200xa
+def exitHandler():
+	print "Exiting"
+	sys.exit(0)
+
+# Register exit handlers
+atexit.register(exitHandler)
+signal.signal(signal.SIGINT, SIGINTHandler)
+
+
+myUln200xa.setSpeed(5) # 5 RPMs
+myUln200xa.setDirection(upmULN200XA.ULN200XA.DIR_CW)
+
+print "Rotating 1 revolution clockwise."
+myUln200xa.stepperSteps(4096)
+
+print "Sleeping for 2 seconds..."
+time.sleep(2)
+
+print "Rotating 1/2 revolution counter clockwise."
+myUln200xa.setDirection(upmULN200XA.ULN200XA.DIR_CCW)
+myUln200xa.stepperSteps(2048)
+
+# release
+myUln200xa.release()
+
+# exitHandler is called automatically

src/uln200xa/CMakeLists.txt

@@ -0,0 +1,5 @@
+set (libname "uln200xa")
+set (libdescription "upm uln200xa darlington stepper driver")
+set (module_src ${libname}.cxx)
+set (module_h ${libname}.h)
+upm_module_init()

src/uln200xa/jsupm_uln200xa.i

@@ -0,0 +1,8 @@
+%module jsupm_uln200xa
+%include "../upm.i"
+
+%{
+    #include "uln200xa.h"
+%}
+
+%include "uln200xa.h"

src/uln200xa/pyupm_uln200xa.i

@@ -0,0 +1,9 @@
+%module pyupm_uln200xa
+%include "../upm.i"
+
+%feature("autodoc", "3");
+
+%include "uln200xa.h"
+%{
+    #include "uln200xa.h"
+%}

src/uln200xa/uln200xa.cxx

@@ -0,0 +1,242 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2015 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <iostream>
+
+#include "uln200xa.h"
+
+using namespace upm;
+using namespace std;
+
+ULN200XA::ULN200XA(int stepsPerRev, int i1, int i2, int i3, int i4)
+{
+  m_stepsPerRev = stepsPerRev;
+  m_currentStep = 0;
+  m_stepDelay = 0;
+  m_stepDirection = 1;          // default is forward
+
+  if ( !(m_stepI1 = mraa_gpio_init(i1)) )
+    {
+      cerr << __FUNCTION__ << ": mraa_gpio_init(i1) failed" << endl;
+      return;
+    }
+  mraa_gpio_dir(m_stepI1, MRAA_GPIO_OUT);
+
+  if ( !(m_stepI2 = mraa_gpio_init(i2)) )
+    {
+      cerr << __FUNCTION__ << ": mraa_gpio_init(i2) failed" << endl;
+      mraa_gpio_close(m_stepI1);
+      return;
+    }
+  mraa_gpio_dir(m_stepI2, MRAA_GPIO_OUT);
+
+  if ( !(m_stepI3 = mraa_gpio_init(i3)) )
+    {
+      cerr << __FUNCTION__ << ": mraa_gpio_init(i3) failed" << endl;
+      mraa_gpio_close(m_stepI1);
+      mraa_gpio_close(m_stepI2);
+      return;
+    }
+  mraa_gpio_dir(m_stepI3, MRAA_GPIO_OUT);
+
+  if ( !(m_stepI4 = mraa_gpio_init(i4)) )
+    {
+      cerr << __FUNCTION__ << ": mraa_gpio_init(i4) failed" << endl;
+      mraa_gpio_close(m_stepI1);
+      mraa_gpio_close(m_stepI2);
+      mraa_gpio_close(m_stepI3);
+      
+      return;
+    }
+  mraa_gpio_dir(m_stepI4, MRAA_GPIO_OUT);
+
+  // set default speed to 1
+  setSpeed(1);
+}
+
+void ULN200XA::initClock()
+{
+  gettimeofday(&m_startTime, NULL);
+}
+
+uint32_t ULN200XA::getMillis()
+{
+  struct timeval elapsed, now;
+  uint32_t elapse;
+
+  // get current time
+  gettimeofday(&now, NULL);
+
+  // compute the delta since m_startTime
+  if( (elapsed.tv_usec = now.tv_usec - m_startTime.tv_usec) < 0 )
+    {
+      elapsed.tv_usec += 1000000;
+      elapsed.tv_sec = now.tv_sec - m_startTime.tv_sec - 1;
+    }
+  else
+    {
+      elapsed.tv_sec = now.tv_sec - m_startTime.tv_sec;
+    }
+
+  elapse = (uint32_t)((elapsed.tv_sec * 1000) + (elapsed.tv_usec / 1000));
+
+  // never return 0
+  if (elapse == 0)
+    elapse = 1;
+
+  return elapse;
+}
+
+
+ULN200XA::~ULN200XA()
+{
+  mraa_gpio_close(m_stepI1);
+  mraa_gpio_close(m_stepI2);
+  mraa_gpio_close(m_stepI3);
+  mraa_gpio_close(m_stepI4);
+}
+
+void ULN200XA::setSpeed(int speed)
+{
+  m_stepDelay = 60 * 1000 / m_stepsPerRev / speed;
+}
+
+void ULN200XA::setDirection(ULN200XA_DIRECTION_T dir)
+{
+  switch (dir)
+    {
+    case DIR_CW:
+      m_stepDirection = 1;
+      break;
+    case DIR_CCW:
+      m_stepDirection = -1;
+      break;
+    }
+}
+
+void ULN200XA::stepperStep()
+{
+  int step = m_currentStep % 8;
+
+  // This motor requires a different sequencing order in 8-steps than
+  // usual.
+
+  //   Step I0 I1 I2 I3
+  //     1  0  0  0  1
+  //     2  0  0  1  1
+  //     3  0  0  1  0
+  //     4  0  1  1  0
+  //     5  0  1  0  0
+  //     6  1  1  0  0
+  //     7  1  0  0  0
+  //     8  1  0  0  1
+
+  switch (step)
+    {
+    case 0:    // 0001
+      mraa_gpio_write(m_stepI1, 0);
+      mraa_gpio_write(m_stepI2, 0);
+      mraa_gpio_write(m_stepI3, 0);
+      mraa_gpio_write(m_stepI4, 1);
+      break;
+    case 1:    // 0011
+      mraa_gpio_write(m_stepI1, 0);
+      mraa_gpio_write(m_stepI2, 0);
+      mraa_gpio_write(m_stepI3, 1);
+      mraa_gpio_write(m_stepI4, 1);
+      break;
+    case 2:    // 0010
+      mraa_gpio_write(m_stepI1, 0);
+      mraa_gpio_write(m_stepI2, 0);
+      mraa_gpio_write(m_stepI3, 1);
+      mraa_gpio_write(m_stepI4, 0);
+      break;
+    case 3:    // 0110
+      mraa_gpio_write(m_stepI1, 0);
+      mraa_gpio_write(m_stepI2, 1);
+      mraa_gpio_write(m_stepI3, 1);
+      mraa_gpio_write(m_stepI4, 0);
+      break;
+    case 4:    // 0100
+      mraa_gpio_write(m_stepI1, 0);
+      mraa_gpio_write(m_stepI2, 1);
+      mraa_gpio_write(m_stepI3, 0);
+      mraa_gpio_write(m_stepI4, 0);
+      break;
+    case 5:    // 1100
+      mraa_gpio_write(m_stepI1, 1);
+      mraa_gpio_write(m_stepI2, 1);
+      mraa_gpio_write(m_stepI3, 0);
+      mraa_gpio_write(m_stepI4, 0);
+      break;
+    case 6:    // 1000
+      mraa_gpio_write(m_stepI1, 1);
+      mraa_gpio_write(m_stepI2, 0);
+      mraa_gpio_write(m_stepI3, 0);
+      mraa_gpio_write(m_stepI4, 0);
+      break;
+    case 7:    // 1001
+      mraa_gpio_write(m_stepI1, 1);
+      mraa_gpio_write(m_stepI2, 0);
+      mraa_gpio_write(m_stepI3, 0);
+      mraa_gpio_write(m_stepI4, 1);
+      break;
+    }
+}
+
+void ULN200XA::stepperSteps(unsigned int steps)
+{
+  while (steps > 0)
+    {
+      if (getMillis() >= m_stepDelay)
+        {
+          // reset the clock
+          initClock();
+
+          m_currentStep += m_stepDirection;
+
+          if (m_stepDirection == 1)
+            {
+              if (m_currentStep >= m_stepsPerRev)
+                m_currentStep = 0;
+            }
+          else
+            {
+              if (m_currentStep <= 0)
+                m_currentStep = m_stepsPerRev;
+            }
+
+          steps--;
+          stepperStep();
+        }
+    }
+}
+
+void ULN200XA::release()
+{
+  mraa_gpio_write(m_stepI1, 0);
+  mraa_gpio_write(m_stepI2, 0);
+  mraa_gpio_write(m_stepI3, 0);
+  mraa_gpio_write(m_stepI4, 0);
+}

src/uln200xa/uln200xa.h

@@ -0,0 +1,157 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2015 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#pragma once
+
+#include <stdint.h>
+#include <sys/time.h>
+
+#include <mraa/gpio.h>
+#include <mraa/pwm.h>
+
+namespace upm {
+
+  /**
+   * @brief UPM support for the ULN200XA series of Darlington Stepper drivers
+   * @defgroup uln200xa libupm-uln200xa
+   * @ingroup seeed gpio motor
+   */
+
+  /**
+   * @sensor uln200xa
+   * @library uln200xa
+   * @comname ULN200XA Stepper Driver
+   * @altname uln2001a uln2002a uln2003a uln2004a
+   * @type motor
+   * @man seeed
+   * @con gpio
+   * @web http://www.seeedstudio.com/depot/Gear-Stepper-Motor-with-Driver-p-1685.html?cPath=39_40
+   *
+   * @brief UPM module for the ULN200XA Darlington Stepper driver
+   *
+   * This module was developed on a ULBN2003A Stepper Driver.  It
+   * should support the uln2001a, 2002a, 2003a, and 2004a devices, for
+   * use in driving a unipolar stepper motor, the 28BYJ-48.
+   *
+   * Example driving a stepper motor
+   * @snippet uln200xa.cxx Interesting
+   */
+
+
+  class ULN200XA {
+  public:
+
+    /**
+     * Enum to specify the direction of a motor
+     */
+    typedef enum {
+      DIR_CW   = 0x01,
+      DIR_CCW  = 0x02
+    } ULN200XA_DIRECTION_T;
+
+    /**
+     * ULN200XA constructor
+     *
+     * @param stepsPerRev number of steps per full revolution
+     * @param i1 digital pin to use for stepper input 1
+     * @param i2 digital pin to use for stepper input 2
+     * @param i3 digital pin to use for stepper input 3
+     * @param i4 digital pin to use for stepper input 4
+     */
+    ULN200XA(int stepsPerRev, int i1, int i2, int i3, int i4);
+
+    /**
+     * ULN200XA Destructor
+     */
+    ~ULN200XA();
+
+    /**
+     * Return the number of milliseconds elapsed since initClock()
+     * was last called.
+     *
+     * @return elapsed milliseconds
+     */
+    uint32_t getMillis();
+
+    /**
+     * Reset the Clock
+     *
+     */
+    void initClock();
+
+    /**
+     * set the speed of the stepper in RPM (Rotation Per Minute
+     *
+     * @param speed speed to set the motor to in RPM's
+     */
+    void setSpeed(int speed);
+
+    /**
+     * set the direction of the motor, clockwise or counter clockwise
+     *
+     * @param dir direction to set the motor to
+     */
+    void setDirection(ULN200XA_DIRECTION_T dir);
+
+    /**
+     * step the stepper motor a specified number of steps
+     *
+     * @param steps number of steps to move the stepper motor
+     */
+    void stepperSteps(unsigned int steps);
+
+    /**
+     * release the stepper, by removing power
+     *
+     */
+    void release();
+
+  private:
+    struct timeval m_startTime;
+
+    // stepper (4-wire)
+    mraa_gpio_context m_stepI1;
+    mraa_gpio_context m_stepI2;
+    mraa_gpio_context m_stepI3;
+    mraa_gpio_context m_stepI4;
+
+    // steps per revolution
+    int m_stepsPerRev;
+    int m_currentStep;
+    uint32_t m_stepDelay;
+
+    /**
+     * step the motor one tick
+     *
+     */
+    void stepperStep();
+
+    /**
+     * step direction - 1 = forward, -1 = backward
+     *
+     */
+    int m_stepDirection;
+  };
+}
+
+