AegiWatch 1.0: a First Smartwatch Prototype

AegiWatch is a standalone smartwatch prototype designed for real-time health tracking and motion detection. Combining the compactness of modern microcontrollers with medical-grade precision sensors, this project demonstrates how to integrate an embedded monitoring system into a small form factor.

The primary objective is to provide instantaneous readings of the user's vital signs and bodily dynamics.

The system relies on a modular architecture optimized for low-power communication and data accuracy:

1. System Brain: A microcontroller (such as the ESP32) that manages data processing and the display.
2. Biometric Sensor (MAX30100 Series): A high-sensitivity photoplethysmogram (PPG) sensor that measures heart rate (BPM) and blood oxygen saturation (SpO_2).
3. Inertial Measurement Unit (IMU6050 - Gyroscope & Accelerometer): Tracks movement across 6 axes (detecting orientation, steps, or a potential fall).
4. Visual Interface: A compact screen (OLED1.3) to display real-time graphs and textual data.
5. Status Indicator & User Input: Features a CNY1 RGB LED for visual alerts or status changes, and a push button for user interaction (such as navigating menus or triggering functions).
6. Power Management: Powered by a rechargeable LiPo battery, safely managed by a TP4056 charging module to handle USB charging and power regulation.
7. Physical Integration: Built on a perfboard (perforated PCB) to securely interconnect all components in a compact layout.

Before assembling the complete system, each component was isolated and tested individually to validate its operation, power consumption, and bus communication:

Biometric Sensor Validation (MAX Series): Testing of the red and infrared LEDs, and calibration of the sensor's sensitivity to obtain a clean PPG signal without interference.

Inertial Measurement Unit (IMU) Calibration: Testing of the accelerometer and gyroscope registers to correct for background noise and drift effects across all 3 axes.

OLED Display Testing: Validation of I2C communication and testing of display scripts to ensure smooth transitions.

Once each module was validated, all components were connected onto a breadboard to create the first fully functional global prototype.

1. I2C Bus Sharing: The MAX sensor, the IMU, and the OLED display were connected in parallel to the microcontroller's shared communication lines (SDA and SCL), with each device assigned its unique hexadecimal address.
2. Power Management: Centralization of the power supply lines ($3.3V$ and GND ground) to stabilize the current and prevent voltage drops during the heart rate sensor's peak measurement spikes.

To transition from a lab circuit to a true wearable form factor, all components were transferred and soldered onto a perforated PCB.

1. Space Optimization: This step eliminated the loose jumper wires from the breadboard, streamlined the architecture to the maximum extent, and allowed for clever module stacking.
2. 'Watch' Form Factor: The soldered circuit became rigid, durable, and compact enough to be integrated directly into an enclosure and worn on the wrist.

To finalize the project and transform the soldered circuit into a truly aesthetic, ergonomic, and wearable object, I designed a custom enclosure using Autodesk Fusion 360 CAD software:

1. Dimensioning and Precise Modeling: Rigorous measurement of the electronic assembly (perforated PCB, sensors, and battery) to model a protective housing tailored down to the exact millimeter, thereby minimizing the overall footprint on the wrist.
2. Ergonomic Optimization for Biometrics: Integration of a dedicated opening at the bottom of the case to guarantee a direct, stable, and comfortable contact between the user's skin and the biometric sensor (MAX series). This is a critical requirement for achieving accurate captures of heart rate (BPM) and oxygen saturation (SpO2) levels.
3. Interface Clearances and Assembly: Design of a perfectly fitted window for the OLED display on the front face, clear access for the battery charging port, and robust side slots for attaching a standard or custom watch strap.

This step covers the firmware implementation for the project. The attached Arduino sketch, montre_simple_01.ino, acts as the central intelligence of the smartwatch, orchestrating data acquisition, processing, and visual feedback.

To ensure seamless hardware abstraction and reliable performance, the code integrates the specific, optimized libraries required for each individual component:

1. I2C Communication & Display: Utilizes the standard Wire.h library alongside dedicated graphics libraries (Adafruit_SSD1306.h and Adafruit_GFX.h) to drive the OLED display with smooth, flicker-free UI transitions.
2. Biometric Tracking: Includes the optimized library for the MAX series sensor to manage register configuration, control the internal red/IR LEDs, and extract clean raw photoplethysmogram (PPG) signals for real-time heart rate and $SpO2$ calculations.
3. Motion Sensing: Integrates the standard IMU driver libraries to poll the 6-axis accelerometer and gyroscope registers, enabling continuous motion tracking and allowing for future digital filtering to cancel out background noise and sensor drift.

The main architecture consists of a rigorous initialization block in setup() to verify all I2C hardware addresses, followed by a non-blocking execution loop in loop() that continuously updates vital signs, monitors motion status, and refreshes the user interface.