Watch

🩺 MedSafe

A medically-aware smartwatch built from silicon up

🌟 Overview

MedSafe is a custom-designed smartwatch platform engineered for real-time health and environmental monitoring. The project spans the full hardware–firmware stack — from KiCad schematics and custom PCB footprints all the way to a modular, multi-sensor ESP-IDF firmware that runs a synchronized 50 Hz acquisition loop across four independent sensors.

The goal: a compact, wrist-worn device that simultaneously tracks heart rate & SpO₂, motion & orientation, altitude & atmospheric pressure, and GNSS location — all in one tightly integrated system.

✨ Key Features

🗂️ Repository Structure

MedSafe/
│
├── 📁 Firmware/                  # ESP-IDF firmware projects
│   ├── 📁 Integration/           # ★ Main multi-sensor integration firmware
│   │   └── main/
│   │       ├── main.c            # App entry & 50 Hz sensor loop
│   │       ├── src/              # Sensor driver implementations
│   │       │   ├── i2c_manager.c
│   │       │   ├── bmp388.c
│   │       │   ├── lsm6dso.c
│   │       │   ├── max30102.c
│   │       │   └── max_m10s.c
│   │       └── include/          # Public driver headers
│   │           ├── i2c_manager.h
│   │           ├── bmp388.h
│   │           ├── lsm6dso.h
│   │           ├── max30102.h
│   │           └── max_m10s.h
│   │
│   ├── 📁 Barometer/             # Standalone BMP388 firmware
│   ├── 📁 IMU/                   # Standalone LSM6DSO firmware
│   ├── 📁 PulseSensor/           # Standalone MAX30102 firmware
│   └── 📁 max_m10s/              # Standalone GNSS firmware
│

🔬 Sensors & Hardware

🫀 MAX30102 — Optical Pulse Oximeter

• Measures raw Red and IR PPG signals via FIFO readout
• Implements AGC (Automatic Gain Control) to adapt LED power to skin tone and ambient light
• DC-bias removal, moving-average filtering, and peak-to-peak detection for BPM computation
• Real-time SpO₂ estimation from the ratio of AC/DC swing between Red and IR channels
• Graceful finger presence detection with automatic sensor reset on removal

📐 LSM6DSO — 6-Axis IMU

• Reads 3-axis accelerometer and 3-axis gyroscope at configurable ODRs
• Computes roll and pitch tilt angles from accelerometer via atan2
• Factory calibration routine averages N samples at rest to zero out bias
• Dual I2C address support (0x6A / 0x6B) with automatic fallback

🌡️ BMP388 — Barometric Pressure Sensor

• High-accuracy temperature-compensated pressure readings
• Converts raw pressure to altitude above sea level using the international barometric formula
• Normal mode with oversampling and IIR filter for stable atmospheric data

🛰️ MAX-M10S — GNSS Module

• Communicates via UBX binary protocol over I2C
• Polls UBX-NAV-PVT messages for:
  • Latitude / Longitude (1e-7 degree precision)
  • Altitude (MSL), speed, horizontal accuracy
  • Fix type (None / Dead Reckoning / 2D / 3D / GNSS+DR / Time)
  • Satellite count, UTC date & time
• Polled at ~1 Hz from within the main 50 Hz sensor loop

⚙️ Firmware Architecture

app_main()
    │
    ├── i2c_manager_init()        ← Shared bus (GPIO 8 SDA / GPIO 9 SCL)
    ├── bmp388_init()
    ├── lsm6dso_init() + calibrate()
    ├── max30102_init()
    ├── max_m10s_init()
    │
    └── xTaskCreatePinnedToCore()
            │
            └── sensor_integration_task()   [Core 0 @ 50 Hz]
                    │
                    ├── bmp388_read_temperature_pressure()
                    ├── lsm6dso_read_data() → lsm6dso_compute_tilt()
                    ├── max30102_read_fifo() → AGC / BPM / SpO₂
                    ├── max_m10s_read_nav_pvt()   [every 50 loops ≈ 1 s]
                    └── printf() combined report   [every 5 loops ≈ 100 ms]

The i2c_manager is a thin singleton that wraps ESP-IDF's i2c_master with mutex-protected register read/write helpers. All four sensor drivers call into it exclusively — no direct I2C calls exist in driver code.

🛠️ Building & Flashing

Prerequisites

• ESP-IDF v5.x
• ESP32-PICO-D4 target board

Build the Integration Firmware

cd Firmware/Integration

# Set the target
idf.py set-target esp32

# Configure (optional)
idf.py menuconfig

# Build, flash, and monitor
idf.py build flash monitor

Build a Standalone Driver

Each sensor subdirectory (Barometer/, IMU/, PulseSensor/, max_m10s/) is an independent ESP-IDF project and can be built identically:

cd Firmware/Barometer
idf.py set-target esp32
idf.py build flash monitor

🔌 Pin Configuration

All four sensors share the same I2C bus. Sensor I2C addresses:

📦 Bill of Materials (Highlights)

Full BOM available at PCB_Files/watch.csv.

📐 PCB & Schematics

The hardware design lives in PCB_Files/ and is a complete KiCad 7 project:

• watch.kicad_sch — Full hierarchical schematic
• watch.kicad_pcb — Routed PCB layout with 3D model references
• watch.kicad_pro — Project configuration and design rules
• footprints_schematics/ — Custom footprint libraries for non-standard packages (e.g., MAX-M10S, MAX30102, FS8205A)

Open in KiCad 7+ for schematic review or PCB manufacturing export (Gerbers, drill files).

🗺️ Roadmap

• OLED display integration (SSD1306 / SH1106)
• BLE data streaming to companion mobile app
• On-device SpO₂ alert thresholds with haptic notification
• GPS track logging to SPI flash
• Low-power sleep / wake-on-motion using LSM6DSO interrupt
• Production enclosure & strap design

📄 License

This project is licensed under the MIT License. See LICENSE for details.