P18037: Team BASE (Biometric + Atmospheric Sensing Earphones)
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Detailed Design

Table of Contents

Team Vision

Throughout the Detailed Design Phase, Team BASE has worked to accomplish:

Progress Report

With 2.5 weeks left until our final Detailed Design review, Team BASE has reflected on the tasks that we have successfully completed thus far and identified the areas that may require more time than initially expected. The following serves as a "Progress Report" update for each of the major sub-systems within our design.

Functional Model

Custom In-ear PPG

Firmware Integration

TL;DR

We have had a few minor scheduling setbacks, but ultimately the key deliverables that we have set for DR4 (Rev 1 PCBs, Rev 2 firmware, "functional prototype") are still on track. We may have less sensor testing completed than expected, but this can be made up over MSD II.

Finalized Electronics

Sensors

Microcontroller

Custom PCBA's

The BME280 and MAX30102 sensors had to be redesigned in order to fit into a headphone form factor. The MAX30102 custom PCBA's are detailed in the Preliminary Detailed Design node. The custom BME280 can be seen below.

 BME280 PCB

BME280 PCB

BOM and Drawings

All required parts and drawings are described in the Family Tree below. Blue boxes indicate mechanical drawings, yellow are electrical drawings and red indicates parts of the project that are out of scope.
 Family Tree

Family Tree

All electrical parts have been documented (see below). A working BOM can be found here

P18037 Completed Drawing Package

P18037 CAD Drawing Sheets

P18037-E001 - WITHDRAWN

P18037-E002 - WITHDRAWN

P18037-E003

P18037-E004

P18037-E005

P18037-E006

P18037-E007

P18037-E008

P18037-E012

System Schematic

Firmware Update

All sensor firmware has been written and verified as working. Further refinements to the code are as follows:

The following documents were employed in designing the firmware

State Diagram

UML Diagram

Use Cases

Sensor Feasibility

Please refer to the Preliminary Detailed Design page for a more detailed account of sensor feasibility testing. Additional testing performed after the Preliminary Detailed Design Review is described below.

PPG Sensor

Location 2 (Behind Ear)

Hyperventilation Testing

Location 3 (In-ear)

The custom in-ear PPG sensor has been assembled. In-ear accuracy testing has been moved to MSD II.

Accelerometer

Accelerometer testing for the BMI160 was performed and indicated that the firmware was correctly operating and that the particular BMI160 on the board was functional.

A preliminary test of the prototype headphones's accelerometer data was conducted, with promising results for determining various factors of the user's motion, such as gait, steps, and general body movement.

Design and Flowcharts

A State Diagram was employed to plan the firmware architecture as well as aid in determining how the user interface will function.

 Firmware State Diagram

Firmware State Diagram

Risk Assessment

As we've progressed with the design, the following risks have been identified. Actions to minimize each risk were developed and will be implemented as needed.

 Risk Mitigation

Risk Mitigation

MSD II Plan

Weeks 1-2

Major Goals

Description
Continue on-the-head, sensor accuracy testing using the functional model and in-ear PPG sensor. Specifically, we'll be examining the effects of heat transfer from the head to the temperature sensor and determining if measuring SpO2 from the ear is feasible.

Weeks 3-6

Major Goals

Description
Based off the results of the sensor testing, the functional model will need to be revised (i.e. thicker material to prevent heat transfer, more insulation, a different earpiece). At this stage, more detailed mechanical drawings will be developed for the earpiece, electronic housing and occipital band. All electronic placements and firmware will be solidified at this time.

Weeks 7-10

Major Goals

Description
At this stage, mechanical documentation will continue to be developed. A simple Android App will be developed and the user experience will be considered. By the end of Week 10, a fully integrated design should be ready to showcase to the customer and guide.

Weeks 11-15

Major Goals

Description
All design work should be finishing up at this stage. Documentation, such as drawings, test plans, test results and user manuals) will be finalized and a technical paper and poster will be produced. MSD II will culminate with Imagine RIT on April 28th, followed by the customer hand-off.

Design Review Materials


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