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Student-designed stethoscope runs Linux

Jan 10, 2008 — by Rick Lehrbaum — 240 views

A team of electrical and computer engineering students at Calvin College is developing an electronic stethoscope based on an embedded Freescale system-on-chip (SoC) running Linux.

The year-long senior project aims to create an electronic stethoscope that will…

  • Record high-quality audio data from a patient’s body
  • Store this audio data in a convenient format
  • Use a USB interface to transfer the audio files to a computer
  • Reduce the amount of ambient noise that a doctor hears
  • Be simple, accurate, and easy to use

Electronic stethoscope functionality
(Source: Rhythm Reloaded project)

A prototype of the stethoscope, currently in development, includes an LCD screen, button interfaces, a hardware CODEC, an electret microphone, flash storage, and a USB interface.

According to the team’s project proposal, “some electronic stethoscopes currently on the market have a few of these features, but none of them combine all of the features into one coherent package.” Additionally, “a survey of the medical community has indicated that medical personnel would respond favorably to the proposed device.”

Electronic stethoscope block diagram
(Click to enlarge; source: Rhythm Reloaded project)

The prototype’s hardware design is based on a Freescale Coldfire MCF5275 system-on-chip (SoC). Among other functions, the SoC integrates a 32-bit microprocessor core, USB device and Ethernet controllers, hardware encryption, and an eMAC (Enhanced Multiply Accumulate Unit). According to the team, the eMAC helps the processor perform the complex computations required for digital filtering and audio compression. An M5275EVB evaluation board, donated by Freescale, is being used for hardware and software development.

On the software side, the team settled on uClinux, an embeddable form of Linux, running from 1MB of flash memory. Prior to selecting uClinux, the team surveyed eight different OSes, rating them for various key requirements, including cost, performance, footprint, etc. Their results are summarized in the following table, and discussed further in the students’ detailed project proposal (referenced below).

Embedded OS selection matrix
(Click to enlarge; source: Rhythm Reloaded project)

Based on the results of this project, the team has concluded that a commercial version of the electronic stethoscope should differ from the prototype in several key aspects. The following recommendations are listed in the Rhythm Reloaded project’s proposal:

  • It needs a wireless chest piece design

  • A more durable, ergonomic, and aesthetically pleasing mechanical design
  • Substitution of a graphical display for the text-only display in the prototype
  • Availability of at least two variants: a “budget model” one for nurses and an “executive model” for doctors
  • Addition of a diagnostic software package for analyzing the recorded body sounds on a computer.

The students’ complete, 81-page project proposal is available as a PDF download from the Rhythm Reloaded project’s website.

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