MicroPython Stepper Motor Driver

Code to drive a 28BYJ-48 motor attached to a ULN2003 driver.

Overview

The module motor.py implements the following classes:

• FullStepMotor -- This class drives a stepper motor using full steps, which with the 28BYJ-48 means 2048 steps for a single rotation.

• HalfStepMotor -- This class drives a stepper motor using half steps, so 4096 steps for a single rotation.

API

Motor objects support the following methods:

• zero() -- set the current position as position 0.
• step(n) -- move forward (positive n) or backwards (negative n) the given number of steps
• step_until(position) -- move motor to the given position. By default the motor will move in the shortest direction, but you can force a direction with the optional dir keyword argument (1 for forward, -1 for reverse).
• step_until_angle(angle) -- move motor to the given angle.

Examples

If you have a ULN2003 connected to a Wemos D1 on pins D5, D6, D7, D8, like this (pinout):

Wemos pin	ULN2003 pin
D5 (GPIO14)	IN1
D6 (GPIO12)	IN2
D7 (GPIO13)	IN3
D8 (GPIO15)	IN4

Then you could create a HalfStepMotor object like this:

import motor
m = motor.HalfStepMotor.frompins(14,12,13,15)

Once you have a motor object, you can run it forward:

m.step(500)

Or backwards:

m.step(-500)

You can run it to a specific position:

m.step_until(2000)

Or to a specific angle:

m.step_until_angle(270)

When using the step_until* methods, the motor will by default move in the direction of shortest distance. You can force a direction with the optional dir keyword argument:

m.step_until(2000, dir=-1)