This research project, carried out in collaboration with Dr. Yasmin Kafai's group at University of Pennsylvania, designed and developed tools to aid novice designers, in particular middle- and high school students, in troubleshooting problems in electronic textile projects.   

Electronic textiles, and more generally craft projects with embedded microcontrollers, have proven to be a vehicle to attract learners to STEM topics -- particularly electronics engineering and software engineering (programming) -- who would otherwise be unlikely to find these topics engaging. 

Inevitably students designing and constructing microcontroller projects encounter bugs: the project does not behave the way they intended or expected.  Whereas students often see bugs as mistakes to be avoided, bugs are also opportunities for students to learn, and sometimes the student may actually prefer the unintended "buggy" behavior, leading to the oft-heard phrase, "It's not a bug, it's a feature."

Microcontroller projects have two major components: hardware and software.  The hardware component is an electronic circuit with sensors such as switches and  light and proximity sensors, actuators such as LEDs and motors, all connected to a microcontroller "brain". The software component is code that prescribes the behavior of the microcontroller, for example lighting LEDs or running motors when certain external conditions are sensed.  Whereas conventional microcontroller projects use wires and a solderless breadboard or printed-circuit board to connect components, electronic textile projects use conductive thread in place of wires, and typically use a special type of microcontroller that is designed for embedding in fabrics, such as the LilyPad Arduino.

Debugging is the process of finding the source of the unexpected behavior and making a change to the circuit or the program to make the project behave as originally intended.  The source of a bug may be in the circuit (such as a broken wire) or the program (such as a misplaced instruction), or it may result from the interaction of the circuit and the program.

Finding and fixing bugs can be frustrating, especially to young and inexperienced learners whose understanding of the underlying principles of electronics and software is incomplete or incorrect. And, unlike physical systems such as plumbing, the electricity flowing through the circuit and the execution of the program is invisible.  For this reason, students need tools to help them locate and understand the behavior of their projects.  Unfortunately, tools and test equipment to troubleshoot microcontroller projects, and especially e-textile projects, are scarce and not designed for inexperienced learners such as middle school students.

This project addressed this problem: designing and developing tools to support inexperienced learners to troubleshoot and debug e-textile projects.  The main tangible project outcomes are a suite of tools that a novice e-textile designer can use to locate the cause of unexpected behavior in an e-textile project (figure 1).

The tools developed are:

• Low-Floor Multimeter, a simple multimeter that provides a continuity tester and a voltage meter.
• The Logic Probe aka Power Check (figure 2)  tests whether a thread in an e-textile circuit is powered or grounded, allowing students to easily test circuits.
  
• The Wrist-Meter (figure 3) combines a voltage meter and a continuity tester that can identify errors while sewing with conductive thread.  It measures the voltage through the needle, and if the voltage drops below a threshold, beeps to prompt the user to immediately locate and fix the error.
  
• The Wearable Mini Voltage Meter is another simplified multimeter, incorporating two alligator clip probes and a large numerical readout.  It can be worn while testing a wearable e-textile project.
  
• The Logic Injector (figure 4)  "injects" a high logic state into a circuit. This tool simulates a digital write high to test circuitry for shorts, loose connections, and polarity.
• The Circuit Playground Extension is a microcontroller holder sewn into an e-textile project, making it possible to easily swap microcontrollers when replacing faulty hardware or testing different programs. It is useful in classrooms where students might exchange programs or the teacher might hand out pre-programmed microcontrollers. 
  
• The ThreadBoard (figure 5) is a version of the solderless breadboard specifically for e-textiles.  Before sewing a circuit into fabric, students can configure the circuit, using stainless steel conductive thread and electronic components that adhere magnetically to the ThreadBoard.  This enables students to experiment with circuit design before sewing the circuit into their fabric.
  
• Circuit Check (figure 6) is a browser-based program for directly observing a microcontroller project, providing support for investigating hardware or software bugs. Circuit Check displays live sensor readings (such as temperature and light) and supports different actuator states (e.g. turning an LED on).  Circuit Check runs alongside the student's program, enabling them to observe their system's internal states while their code is running and allows them to pause the program to isolate and test hardware components.

Last Modified: 01/17/2023
Modified by: Ann N Eisenberg