Discreet Answers

[a discreet responder before applying foot pressure] [a discreet responder while applying foot pressure]

“Tell your teacher you don't understand, without the fear of your classmates knowing”


Discreet Answers is designed to enable students to discreetly notify their teachers—without their classmates' knowing—of their confusion regarding a topic presented in class.  This process is carried out by a device called a Discreet Responder, or DR, which is a box containing a wireless module and a sensor that tracks foot pressure.  Each student is given a DR, which has a serial number that identifies each student to the software running on the teacher's computer.  Since the DR is foot–controlled, it remains out of sight and discreet.

When a student doesn't understand a topic, after a teacher asks, “did that make sense?”, the student has the option of answering before the entire class, like most people, or, if the student is too shy, discreetly pressing his or her DR. The student can also notify the teacher of just how much he or she doesn't understand by the amount of pressure exerted on the DR: harder pressure translates to a greater degree of obfuscation, while a lighter press means the topic is confusing, but not too much. Only the teacher is aware, via a computer, of who pressed their DRs and by how much.


This project is designed specifically for teachers/instructors to use with all students.   In an ideal classroom situation, only those students too shy to acknowledge confusion before their classmates would actually use it.

User Scenario

A teacher presents a topic to the class.  Before moving on to the next topic, which builds upon the understanding of the previous topic, he/she asks the students, “did that make sense?”   Every student will either answer “yes,” “no,” ask the teacher to clarify, or remain quiet.  The silent ones are either not paying attention, don't care to answer (because they understand), or are embarrassed to say they don't understand, for fear that their peers will perceive them as dumb.  It is these quiet, shy students who would choose to answer discreetly by pressing on their DRs.  The more each student doesn't understand, the greater the pressure he/she exerts on his/her DR.  The teacher sees on his/her computer exactly who didn't understand, and by how much each student didn't understand.

The teacher can now gauge the class' understanding. How many didn't understand? Of those who didn't understand, by how much did they not understand? He/she can now formulate his/her re–explaining of the previous material, based on how many didn't understand, and by how much.


A flickr set



Discreet Answers is implemented in a combination of both hardware and software. In hardware, one XBee radio receives data while two or more DRs send data. In software, a small program running in The Terminal interprets the receiving data and parses according to individual student.

The DRs are simple: one XBee radio, two LEDs, a miniature trim potentiometer (trim pot), two AA batteries, and a force–sensing resistor (FSR).  The XBee wirelessly transmits to a computer the pressure read by the FSR.  The LEDs are used to indicate power and transmission.  They're present for debugging purposes only, and are hidden under the cover of each device.  The trim pot regulates the serial data read by the FSR. And, the batteries power the entire device.

At the computer end, all the DRs feed wireless data to one receiving XBee connected to an Arduino. The Arduino, which is physically connected via USB to a computer, parses the serial data received from all the devices, then prints a report of each DR's FSR pressure.

XBee Configuration

Three XBee radios were used in the prototype of this project. The first was configured to receive data streaming in from the other two, communicating that data to my computer. This receiver was setup as a coordinator in API mode.

The other two radios, the DRs, acted as senders and were configured as routers in AT mode.

The senders sampled their 20th pin (ATD0) once every second (ATIR3E8, where 3E8hex represents 1000dec, or one second), then sent that sampled data to the receiving coordinator radio (ATDH and ATDL), which transmitted the packets to an Arduino microcontroller.

Receiver (× 1) — Coordinator API
Senders (× 2) — Router AT


Using UNIX's screen command, the software parses the incoming serial data according to student, then presents it on the 10th line, 5th column for the first student and the 11th line, 5th column for the second student. The simple prototype feedback screen looks like:

[screen dump of terminal running discreet answers]

Separate Files (viewable in a browser)

This code and radio configuration will work for any project in which serial data from a sensor is sent from two radios to one coordinator (configured according to the above specs). If you decide to use this code, remember that all the files must be in a folder titled discreet_answers, and that the pde file must be titled discreet_answers.pde. Your sketch should look like:

[arduino sketch of discreet_answers arduino project]


Teachers/instructors/educators: If you want to keep abreast of this project's progress, or you'd like to order a kit, please fill out the form below.

Students: If you think you can benefit from using this project, notify your teacher/instructor/educator. Of course, if you're simply interested in the development of Discreet Answers, you're welcome to join the list.

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r . o . y a t n y u d o t e d u

Roy Vanegas
Last modified: Fri Dec 19 22:35:32 EST 2009