StepperMotor

2 Modules for controlling unipolar stepper motors. The first - listed below - is simple but occupies the PIC 100% whilst the motor is moving. The 2nd - listed here - is interrupt driven so the main program can get on with other things whilst the motor is moving to its new position.

Simple Stepper Motor Module

Motor may be connected to any four pins on one port.

Subs and Functions

(see code for parameters and other information)

Note: All angles are * 100 (i.e. 90 degrees in reality = 9000 in module)

Move - moves motor specified number of steps with given direction and speed.

MoveToPosition - moves motor as close as possible to specified degree position (0 - 359.99) with given direction and speed.

ShortestMoveToPosition - moves motor in the shortest direction as close as possible to specified degree position (0 - 359.99) with given speed.

MoveToLimit - moves motor in specified direction until a given PIC pin goes high. Can be used with a limit switch for calibrating the system to a known position. Optional StepTimeout sets number of steps after which movement stops regardless of limit switch state.

ResetPosition - sets module's Position variable to specified value. Useful for setting zero point after MoveToLimit or other calibration.

Rotate - turns motor through a given number of complete revolutions.

PowerOff / PowerOn - stops / resumes output on stepper motor pins.

GetPosition - returns current degree position of motor (0 - 359.99)

GetStep - returns current step number (1 - 8)

Options

#option Stepper_Port = PORTB               'Which PORT stepper is connected to

#option Stepper_Pin1 = %00000001           '}
#option Stepper_Pin2 = %00000010           '}Which 4 pins the stepper motor is
#option Stepper_Pin3 = %00000100           '}connected to. (Pins 0-3 shown here)
#option Stepper_Pin4 = %00001000           '}

#option Stepper_FullStepSize = 750         'Degrees motor moves in one full step
#option Stepper_HalfStepMode = True        'Drive motor in half step mode?
#option Stepper_DefaultSpeed = 4           'Default delay in mS between steps

#option Stepper_LimitSwitch = PORTB.4      'Pin which limit switch is connected to.
                                           'Note: Active HIGH

Usage Example

#option Stepper_Port = PORTB            '}
#option Stepper_Pin1 = %00000001        '}Stepper connected to pins 0,2,3 & 5
#option Stepper_Pin2 = %00000100        '}of PORTB
#option Stepper_Pin3 = %00001000        '}
#option Stepper_Pin4 = %00100000        '}

#option Stepper_FullStepSize = 500      'Full step is 5 degrees
#option Stepper_HalfStepMode = True     'Drive stepper in half-step mode
#option Stepper_DefaultSpeed = 4        'Default 4mS between steps

#option Stepper_LimitSwitch = PORTA.0   'Pin for limit switch


Include "Stepper.bas"

Dim MotorPosition As Word

Const Clockwise = True
Const AntiClockwise = False

'Set PortA.0 to input (limit switch)
TRISA = %00000001


'Move motor 10 steps clockwise at default speed
Stepper.Move(Clockwise, 10)


'Move motor anti-clockwise at 8mS between steps until it reaches limit switch.
'If limit switch not reached after 100 steps then stop driving motor.
If Stepper.MoveToLimit(AntiClockwise, 8, 100) Then

     'Limit switch reached succesfully, set zero point     
     Stepper.ResetPosition(0)

Else

    'Limit switch not reached, must be a mechanical problem, turn off motor
    Stepper.PowerOff()

EndIf


'Move motor to 120 degrees in shortest direction, store new position in variable
MotorPosition = Stepper.ShortestMoveToPosition(12000)


'Rotate 3 1/2 times clockwise:

    'First do three complete revolutions
    Stepper.Rotate(3, Clockwise)

    'Then move to a position 180 degrees from the current position 
    Stepper.MoveToPosition(Stepper.GetPosition() + 18000, Clockwise)

Module Code

{
********************************************************************************
*  Name    : Stepper Motor Module                                              *
*  Author  : AndyO                                                             *
*  Notice  : Copyright (c) 2008 AndyO                                          *
*          : All Rights Reserved                                               *
*  Date    : 01/03/2008                                                        *
*  Version : 1.0                                                               *
*  Notes   : For use with 4 phase unipolar stepper motor                       *
*          :                                                                   *
*          : All angles * 100 (i.e. 7.5deg in reality = 750 in module)         *
********************************************************************************
}

Module Stepper 

Include "Math.bas"


'===============================================================================
'User definable options
'-------------------------------------------------------------------------------

#option Stepper_Port = PORTB               'Which PORT stepper is connected to

#option Stepper_Pin1 = %00000001           '}
#option Stepper_Pin2 = %00000010           '}Which 4 pins the stepper motor is
#option Stepper_Pin3 = %00000100           '}connected to. (Pins 0-3 shown here)
#option Stepper_Pin4 = %00001000           '}

#option Stepper_FullStepSize = 750         'Degrees motor moves in one full step
#option Stepper_HalfStepMode = True        'Drive motor in half step mode?
#option Stepper_DefaultSpeed = 4           'Default delay in mS between steps

#option Stepper_LimitSwitch = PORTB.4      'Pin which limit switch is connected
                                           'to.  Note: Active HIGH


#option Stepper_TRIS = getTRIS(Stepper_Port)


'===============================================================================
'Variable and Const Declarations
'-------------------------------------------------------------------------------

'---Bring options into module

Private Const
    #if Stepper_HalfStepMode Then

        StepJump = 1,
        StepSize = Stepper_FullStepSize / 2,

    #else

        StepJump = 2,
        StepSize = Stepper_FullStepSize,

    #endif

    Pin1 As Byte = Stepper_Pin1,
    Pin2 As Byte = Stepper_Pin2,
    Pin3 As Byte = Stepper_Pin3,
    Pin4 As Byte = Stepper_Pin4,


    'PortMask used to turn on/off only the pins the stepper is connnected to

    PortMask As Byte = Not(Pin1 Or Pin2 Or Pin3 Or Pin4),


    'Step masks used to turn on the correct pins for the current step.
    'Constant array loaded with half-step sequence    

    StepMask(8) As Byte = (Pin1,                                   'Step 1: 0001
                           Pin1 Or Pin2,                           'Step 2: 0011
                           Pin2,                                   'Step 3: 0010
                           Pin2 Or Pin3,                           'Step 4: 0110
                           Pin3,                                   'Step 5: 0100
                           Pin3 Or Pin4,                           'Step 6: 1100
                           Pin4,                                   'Step 7: 1000
                           Pin4 Or Pin1),                          'Step 8: 1001


    DefaultSpeed = Stepper_DefaultSpeed


Private Dim
    StepperPort As Stepper_Port,
    LimitSwitch As [email protected],
    StepperTRIS As Stepper_TRIS


'---Other Dims

Private Dim CurrentStep As Byte
Private Dim Position As Word

Private Dim DistanceClockwise As Word
Private Dim DistanceAntiClockwise As Word

Private Dim StartingPosition As Word  


'===============================================================================
'Helper Subs and Functions (Private - can't be called from main program)
'-------------------------------------------------------------------------------

Private Sub SingleStep(pRotateClockwise As Boolean)

    If pRotateClockwise Then                            
        CurrentStep = CurrentStep + StepJump

        Position = Position + StepSize

        If Position > 35999 Then
            Position = Position - 36000

        EndIf

    Else                                                    
        CurrentStep = CurrentStep - StepJump

        'Check for zero cross and update Position variable accordingly
        If Position >= StepSize Then
            Position = Position - StepSize

        Else
            Position = (36000 + Position) - StepSize

        EndIf

    EndIf                                                   


    Select CurrentStep                                      

        Case >8                                              
            CurrentStep = StepJump                                 

        Case 0                                              
            CurrentStep = 8                                 

    EndSelect                                               


    'AND'ing Port with PortMask sets only stepper pins to '0', ignores others
    'OR'ing Port with StepMask for current step sets the relevant pins high

    StepperPort = (StepperPort And PortMask) Or StepMask(CurrentStep - 1)

End Sub



'===============================================================================
'Public Subs and Functions
'-------------------------------------------------------------------------------

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
'Name:      Move
'Purpose:   Moves stepper with specified direction, number of steps and speed
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Public Sub Move(pRotateClockwise As Boolean = True, pNumberOfSteps As Word = 1, pSpeed As Byte = DefaultSpeed)

    While pNumberOfSteps > 0

        SingleStep(pRotateClockwise)
        DelayMS(pSpeed)
        Dec(pNumberOfSteps)

    Wend

End Sub



'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
'Name:      MoveToLimit
'Purpose:   Moves stepper with specified direction and speed until limit switch
'           is triggered.  Optional pStepTimeout sets number of steps after 
'           which movement stops regardless of limit switch state.
'
'Returns:   True if limit switch reached before pStepTimeout,
'           False otherwise
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Public Function MoveToLimit(pRotateClockwise As Boolean = True, pSpeed As Byte = DefaultSpeed, pStepTimeout As Word = 0) As Boolean

    If pStepTimeout > 0 Then
    'Timeout has been specified                     

        While LimitSwitch = 0 And pStepTimeout > 0   

            SingleStep(pRotateClockwise)             
            DelayMS(pSpeed)                          

            Dec(pStepTimeout)

        Wend

        If pStepTimeout = 0 Then
            result = False

        Else
            result = True

        EndIf

    Else
    'No timeout specified

        While LimitSwitch = 0                        

            SingleStep(pRotateClockwise)
            DelayMS(pSpeed)

        Wend

        result = True

    EndIf


End Function



'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
'Name:      ResetPosition
'Purpose:   Sets Position variable to specified value.  Useful for setting zero
'           point after move to limit switch or other calibration.
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Public Sub ResetPosition(pPosition As Word = 0)

    Position = pPosition

End Sub    



'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
'Name:      MoveToPosition
'Purpose:   Moves stepper as close as possible to desired position with
'           specified direction and speed.
'
'           Note: All positions * 100 i.e. 90 deg = 9000
'
'Returns:   Actual final position of stepper.  May vary from desired position
'           due to resolution of step size.
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Public Function MoveToPosition(pDesiredPosition As Word, pRotateClockwise As Boolean = True, pSpeed As Byte = DefaultSpeed) As Word

    'If desired position is 360deg or over then bring it into 0 - 35999 range

    If pDesiredPosition > 35999 Then

        pDesiredPosition = pDesiredPosition - 36000

    EndIf


    'Keep making steps until the actual position is within 1/2 a step of the
    'desired position (closest we can get).

    '2nd condition prevents problems caused around 360 / 0 degrees.
    'i.e. without it then if desired position is 35999 and actual position is 0
    'then the code will loop forever as Desired - Actual = 35999

    While Math.abs(pDesiredPosition - Position) > StepSize / 2 And
          Math.abs(pDesiredPosition - Position) < 36000 - (StepSize / 2)

        SingleStep(pRotateClockwise)
        DelayMS(pSpeed)

    Wend

    result = Position

End Function



'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
'Name:      ShortestMoveToPosition
'Purpose:   Moves stepper as close as possible to desired position with
'           specified speed in the shortest direction.
'
'           Note: All positions * 100 i.e. 90 deg = 9000
'
'Returns:   Actual final position of stepper.  May vary from desired position
'           due to resolution of step size.
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Public Function ShortestMoveToPosition(pDesiredPosition As Word, pSpeed As Byte = DefaultSpeed) As Word

    'If desired position is 360deg or over then bring it into 0 - 35999 range

    If pDesiredPosition > 35999 Then

        pDesiredPosition = pDesiredPosition - 36000

    EndIf


    'Calculate distance between desired and actual position in each direction

    If pDesiredPosition > Position Then

        DistanceClockwise = pDesiredPosition - Position
        DistanceAntiClockwise = (36000 - pDesiredPosition) + Position

    Else

        DistanceClockwise = (36000 - Position) + pDesiredPosition
        DistanceAntiClockwise = Position - pDesiredPosition

    EndIf

    'Call MoveToPosition function.  Rotation direction determined by whether
    'distance in clockwise direction is smaller than distance anticlockwise  

    result = MoveToPosition(pDesiredPosition, DistanceClockwise < DistanceAntiClockwise, pSpeed)


End Function



'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
'Name:      Rotate
'Purpose:   Rotates stepper the specified number of complete revolutions with
'           specified direction and speed.
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Public Sub Rotate(pNumberOfRotations As Byte = 1, pRotateClockwise As Boolean = True, pSpeed As Byte = DefaultSpeed)

    While pNumberOfRotations > 0

        StartingPosition = Position

        SingleStep(pRotateClockwise)
        DelayMS(pSpeed)

        While Position <> StartingPosition

            SingleStep(pRotateClockwise)
            DelayMS(pSpeed)

        Wend

        Dec(pNumberofRotations)

    Wend

End Sub

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
'Name:      PowerOff
'Purpose:   Stops all output on stepper pins
'
'           Note: Stepper won't hold position
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Public Sub PowerOff()

    StepperPort = StepperPort And PortMask

End Sub



'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
'Name:      PowerOn
'Purpose:   Resumes output on stepper pins
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Public Sub PowerOn()

    StepperPort = (StepperPort And PortMask) Or StepMask(CurrentStep - 1)

End Sub



'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
'Name:      GetStep  
'Returns:   Number of current step (1 - 8)
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Public Function GetStep() As Byte

    result = CurrentStep

End Function



'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
'Name:      GetPosition
'Returns:   Current stepper position (0 - 35,999)
'
'           Note: All positions * 100 i.e. 90 deg = 9000
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Public Function GetPosition() As Word

    result = Position

End Function



'===============================================================================
'Module Initialisation
'-------------------------------------------------------------------------------

'Initialise vars
CurrentStep = StepJump
Position = 0

'Set TRIS without changing non-stepper pins
StepperTRIS = StepperTRIS And PortMask