RPistepper 0.3a1

Conections RPi - ULN2803A:

Conections ULN2803A - Motors:

In this case, two motors were attached to the ULN2803A.

class Motor

This class allows the user to control a 6 pin stepper motor using 4 GPIO pins of a RPi.

Software uses BCM mode for pin indexing.

This class is best used with the ‘with’ statement to properly handle the cleanup of the GPIOs.

self.steps is a property of this class that will get the number of steps taken from the initial position or set to a specific step, similar to self.move.

In order to save power, it’s advised to call self.release() when the motor is idle.

Arguments are a list with the 4 pins (Coil_A1, Coil_A2, Coil_B1, Coil_B2), the delay between steps (default = 20ms) and verbose to display reports on the motor movements, the last two are optional. e.g:

import RPistepper as stp
M1_pins = [17, 27, 10, 9]
with stp.Motor(M1_pins) as M1:
    for i in range(10):               # moves 20 steps,release and wait
        print M1
        M1.move(20)
        M1.release()
        raw_input('enter to execute next step')

If the class is instantiated normally, use the method cleanup prior to closing the application to close the GPIO resources. Also, if it’s important to go back to the initial position when finishing the routine, use the method reset.

import RPistepper as stp
M1_pins = [17, 27, 10, 9]
M1 = stp.Motor(M1_pins)
for i in range(10):               # moves 20 steps,release and wait
    print M1
    M1.move(20)
    M1.release()
    raw_input('enter to execute next step')
M1.reset()
M1.cleanup()

Methods

Currently there are five implemented methods:

def move(self, steps):
    '''
    Moves the motor 'steps' steps. Negative steps moves the motor backwards
    '''

def release(self):
    '''
    Sets all pins low. Power saving mode
    '''

def reset(self):
    '''
    Returns the motor to it's initial position
    '''

def zero(self):
    '''
    Sets the motor to the next position which Coil_A1 and Coil_A2
    are on. Sets this position as the reference (steps = 0).
    '''

def cleanup(self):
    '''
    Cleans the GPIO resources
    '''

The main method is move, which moves the motor the desired number of steps

steps property

It’s possible to check the motor position or manually set the desired step using the steps property:

import RPistepper as stp
M1_pins = [17, 27, 10, 9]
with stp.Motor(M1_pins) as M1:
    for i in range(10):               # moves 20 steps,release and wait
        print M1.steps
        M1.steps = 20*i
        M1.release()
        raw_input('enter to execute next step')
    M1.reset()

Attributes

This class haves the following attributes:

def zig_zag(motor1, motor2, amp1, amp2, delay=None):
    '''
    Executes a zig-zag movement with two RPistepper objects.
    Arguments are: motor1 and motor2 objects and amp1, amp2, the amplitude
    of movement, a tuple (step, rep) representing the number of steps per
    iteration and the number of iterations of the following algorithm:
        Repeat rep1 times:
            1. Moves motor 2 step2*rep2 steps forward
            2. Moves motor 1 step1 steps forward
            3. Moves motor 2 step2*rep2 steps backwards
            4. Moves motor 1 step1 steps forward
        Reset to initial state
        Release the motors
    It's possible to change the delay between steps with the 'delay' argument
    '''

def square_spiral(motor1, motor2, amplitude, delay=None):
    '''
    Executes a square spiral movement with two RPistepper objects.
    Arguments are: motor1 and motor2 objects and the amplitude of movement,
    a tuple (step, rep) representing the number of steps per iteration and
    the number of iterations of the following algorithm:
        for i in range(rep):
            1. Moves motor 2 to position i
            2. Moves motor 1 to position i
            3. Moves motor 1 to position -i
            4. Moves motor 2 to position -i
        Reset to initial state
        Release the motors
    It's possible to change the delay between steps with the 'delay' argument
    '''