P19001: Wearable Interface

Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

The Team plan for this phase was to complete testing of the individual components of the Dext identified in the system design review, and start testing the three Dext prototypes the team decided to move forward with: Concepts 1,2 and 4.

During this phase, the preliminary arduino code testing the IMU and the Bluetooth were successfully completed and tested with the IMU currently able to recognize 4 unique hand positions with further design required to calculate yaw. A lookup table for the MCU code to use for reference was completed, as well as psuedo-code for the main software. The prototype for Concept 1 was successfully demoed during presentation without the IMU or lookup table setup, showing that at least one prototype will likely be completed before MSD II.

It was determined that the 1-axis Hall effect sensors used in testing for Concept 2 would not be able to be used for the desired task, however further testing will occur using a 3-axis Hall effect sensor. The TOF sensors used in Concept 4 have yet to be tested.

Prototyping, Engineering Analysis, Simulation

IMU Simulations

Using the accelerometer in Adafruit LSM9DS1

There are difficulties calculating Yaw for now, but the expected positions of the Dext will not require Yaw readings. Future iterations that support typing with the hand at one’s side may implement Yaw through fusion of the magnetometer along with the other 6 axes of measurement through a Complementary Filter.

The code used for the IMU testing can be found here. The two libraries used are respectively the Adafruit LSM9DS1 Library and the Adafruit Sensor Master Library

Bluetooth Simulations

Some additions made:

Some Oddities:

Bluetooth test Code

Bluetooth test Code

Overall, BLE testing was successful in producing a usable keyboard. Once the other components are attached, keyboards will be mapped to hand orientations. Further research will be conducted to reduce errors and maximize performance.
Bluetooth tests

Bluetooth tests

The code used for the Bluetooth testing can be found here.

Hall Effect Testing

Four 1-axis sensors were mounted on hand-strap and fed into a micro-controller which calibrated readings for fingers up and fingers down, then used those as thresholds for future readings. 1-axis Hall Effect sensors were ruled out due to lateral movements and disturbances being interpreted incorrectly
Hall Effect Tests

Hall Effect Tests

The code used to test the Hall Effect sensors can be found here.

MCU Psuedocode

The code from the previous teams design was altered to allow for the new prototype design, with the lookup table updated based on most commonly used characters.

The edited psuedocode can be seen here.

A section of the Lookup Table in Excel is shown below

Lookup Table

Lookup Table

It is used in the C++ code for the keyboard hashmap to designate certain characters, the code can be viewed here (with the header file here ).

Concept 1 Prototype Schematic

Concept 1 Prototype Schematic

The schematic above is a representation of the possible finished prototype, as the Bluetooth is an internal piece of the MCU it only requires the connection of the 4 finger sensors and the IMU.

Drawings, Schematics, Flow Charts, Simulations

The modules tested were all taken from the Systems Architecture below. The IMU, Bluetooth connectivity, MCU, Sensors, and the design were all individually tested and considered.
System Architecture

System Architecture

Materials used and the Hardware design were considered separetely and the presentation on the possible materials can be seen here.

Bill of Material (BOM)

Proposed BOM

Proposed BOM

This is the current Proposed BOM it has yet to be updated with prices as decisions for the prototypes are still being made.

Plans for next Phase

Design and Flowcharts

MCU Design Flow

MCU Design Flow

Risk Assessment

Risk Assessment

Risk Assessment

Design Review Materials

Problem Definition Presentation
System Level Design Review Presentation
Preliminary Detailed Design Review Presentation

Plans for next phase

Team Member 3-week Plans

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