Embedded Files
Overview & Description
This wallet uses an E-ink display and an open-source financial tracking application to show the user's monthly spending and budget categories.
For practicality, the wallet includes a speaker that will beep for location finding, USB-C charging, and a reed switch for power on/off with wallet movement.
Features
Power
3.7V 500MAH Rechargeable LiPo Battery
3.3V to 5V Boost Switching Regulator
USB-C Charging Port
Compute
ESP32-S3-WROOM-1 Microcontroller
SPI Communication
Bluetooth to Connect to Budgeting App
Actuation
8 Ohms General Purpose Speaker
Audio Amplifier Circuit and Coupling Capacitors
Responds to Interrupt in Bluetooth Signal
Actuation
2.9" Flexible Monochrome E-paper Display
Responds to ESP32
Bill of Materials, Total Cost: $61.63
Schematic
Completed Schematic with LiPo Battery Charging through USB-C, Audio Control,
Display Actuation, and Start/Reset Switches
Layout
Completed Layout, Front
Completed Layout, Back
Completed Layout, Full
3D Render of PCB
Firmware
Program to test functionality of speaker. Beeps 3 times then no longer plays audio which is what we'll use to notify the user of losing Bluetooth connectivity.
Snippet of program trying to setup BLE connection from ESP32 to iPhone. This is still a work in progress.
Summary of Work
Issues
Issues
No silk screen! As you can see on our board, something happened in production to leave out our silk screen. This was simply fixed by referencing the layout heavily throughout the assembly process.
Debugging and adjusting to errors in our design. An example is that our reset button was oriented such that GPIO 0 on the ESP32 was always shorted to ground so the ESP32 enable pin would never be on.
Learnings
Learnings
Our reed switch was positioned in the center of the board, leading it to be vulnerable to other signals and components. We had to solder it on last in a very tight area.
Definitely use a stencil or induction methods as opposed to hand soldering the components, especially some of the smaller ICs.
Triple check the orientation of the components. We had a few that were rotated by 90 degrees in schematic and/or layout and had to find workarounds.
Future Work
Future Work
Condense the layout more. We enlarged it during the design stage to see our connections better, but never resized it after. There's a lot of empty space on the board currently.
Implement a touchscreen that can be used to switch between screens, similar to a smart watch.
Modify a wallet and put our board in.
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