Remote Lab: Interrupt-Driven Stepper Motor Control

Most embedded systems students learn about polling—constantly checking for events in a loop. But real-time systems need interrupts to respond instantly to external events. Our Interrupt Motor Control Lab teaches interrupt programming by building a stepper motor controller with visual position feedback on a 24-LED ring.

The lab teaches interrupt-based programming by having students replace inefficient polling with hardware interrupts. Students learn to:

The practical application? A 28BYJ-48 stepper motor with a magnetic pointer that triggers a Hall sensor. As the motor rotates, a LED ring displays the pointer’s position in real-time—synchronized through interrupts.

Before accessing real hardware, students work through a debugging exercise in the AVR8js simulator. A broken program attempts to toggle an LED using button interrupts, but contains common errors:

Students must identify and fix these errors, building confidence with interrupt configuration before working with physical hardware. The simulator provides immediate feedback with a virtual button and LED.

Students then tackle the real application: an interrupt-driven motor position tracker using:

The starter code uses inefficient polling—constantly checking digitalRead(2) to detect the sensor. Students improve it through three tasks:

Task 1 - Interrupt Configuration: Implement an ISR triggered on falling edge of the Hall sensor. The ISR resets a global volatile int position variable to 0 when the magnet passes.

Task 2 - Replace Polling: Remove the if (digitalRead(2) == 0) polling logic and rely entirely on the interrupt-driven position reset.

Task 3 - LED Visualization: Map the motor’s position (0-2048 steps) to the LED ring (0-23 LEDs), displaying the pointer’s angular position as it rotates through 3 full revolutions.

Students write code in the Editor Module, upload via Terminal Module, and watch live video of the motor spinning with synchronized LED feedback through the Streaming Module.

This lab teaches interrupt fundamentals through practical application. Students learn:

The skills apply directly to robotics, industrial automation, user interfaces, and any system requiring immediate response to external events. The Code Logger Module anonymously captures student work, helping instructors identify common challenges and improve the curriculum.

The lab demonstrates how Edrys-Lite makes hands-on embedded systems education accessible without requiring students to own hardware or visit physical labs. Students at TU Bergakademie Freiberg complete these exercises remotely, gaining practical skills from anywhere with internet access.

Ready to teach interrupt programming through hands-on remote experimentation? Build your motor control lab with Edrys-Lite!

Explore the lab: github.com/edrys-labs/lab-tubaf-embedded-systems

Learn more about Edrys-Lite: edrys-labs.github.io