Table of Contents
Team VisionThroughout the Detailed Design Phase, Team BASE has worked to accomplish:
- A 3D-printed, functional model with all sensors loosely integrated;
- On-the-head sensor testing; and
- A custom, in-ear PPG sensor.
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.
- The functional model was updated and sent to be 3D-printed using ABS plastic on 11/21.
- Once received (expected 12/3), all electronics (sensors, microcontroller) will be integrated into the model.
- If time permits, more on-the-head testing will be performed to verify the accuracy of the sensors.
Custom In-ear PPG
- The in-ear PCB board has been soldered and connections verified under x-ray.
- The PPG main board had to be reordered (expected 11/27), putting our in-ear feasibility testing behind schedule. Once received, the sensor firmware will be uploaded to the board and testing will resume.
- All sensor firmware has been integrated into a single script.
- We are currently in the process of establishing a debugging environment (Eclipse).
TL;DRWe 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.
- BME280: Environmental Unit
- BMI160: Accelerometer/Gyroscope
- MAX30102: PPG
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.
BOM and DrawingsAll 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.
All electrical parts have been documented (see below). A working BOM can be found here
Firmware UpdateAll sensor firmware has been written and verified as working. Further refinements to the code are as follows:
- Convert code to interrupt/timer based
- Data logging
- Write data to SD or flash
- Download stored data over serial/USB
- Power management
- Phone application (time permitting)
- Bluetooth (time permitting)
The following documents were employed in designing the firmware
Sensor FeasibilityPlease 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.
Location 2 (Behind Ear)
- Due to test set-up limitations, reliable data was unable to be measured.
- Breathing into a bag causes a lot of head movement leading to a noisy signal
- Holding sensor against the head causes instability and lack of repeatability
Location 3 (In-ear)
The custom in-ear PPG sensor has been assembled. In-ear accuracy testing has been moved to MSD II.
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.
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.
MSD II Plan
Weeks 1-2Major Goals
- Review design
- Continue sensor testing
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 3-6Major Goals
- Revise functional model based off testing results
- Begin working on user experience
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 7-10Major Goals
- Develop Android app
- Fully integrated system demo
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 11-15Major Goals
- Finish all documentation
- Customer hand-off & Imagine RIT
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
- Notes from review
- Action Items