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Dual-ESP32 Medical Monitoring System

Overview

A secure IoT medical monitoring and access control system using two ESP32 microcontrollers with ESP-IDF framework. Real-time vital monitoring with fall detection, posture recognition, and RFID-based access control.

Architecture

┌──────────────────────────────────────────────────────────┐
│           HiveMQ Cloud MQTT Broker (TLS)                 │
│              mqtts://*.eu.hivemq.cloud:8883              │
└────────────────────────▲─────────────────────────────────┘
                         │ MQTT over TLS
                         │
         ┌───────────────┴──────────────┐
         │                              │
    ┌────▼──────────────┐      ┌───────▼─────────┐
    │    Node A         │      │    Node B       │
    │  (Vital Monitor)  │      │   (Sentry)      │
    │                   │      │                 │
    │ - MPU6050 (Fall)  │      │ - RC522 RFID    │
    │ - DHT11 (Temp)    │      │ - IR Motion     │
    │ - HW-827 (Heart)  │      │ - Buzzer Alarm  │
    │ - Button (SOS)    │      │                 │
    └──────────┬────────┘      └────────┬────────┘
               │ ESP-NOW P2P           │
               └───────────────────────┘
                  (Emergency alerts)

Hardware Requirements

Node A: Vital Monitor (Medical Monitoring)

  • Microcontroller: ESP32 DevKit V1
  • Sensors:
    • MPU6050 (I2C: GPIO 21/22) - 6-axis IMU for fall detection + posture
    • DHT11 (GPIO 5) - Temperature & humidity (1-wire protocol)
    • HW-827 (GPIO 36, ADC) - Heart rate sensor
    • Emergency Button (GPIO 4, active LOW) - Manual SOS trigger

Node B: Sentry (Access Control & Security)

  • Microcontroller: ESP32 DevKit V1
  • Sensors:
    • RC522 RFID Reader (SPI: GPIO 23/25/19/22) - Access control
    • IR Motion Sensor (GPIO 13) - Intrusion detection
    • Buzzer (GPIO 5, NPN driver) - Alarm output

Common Requirements

  • 3.3V power via AMS1117 regulator
  • USB-C or Li-ion battery (3.7-4.2V)
  • Breadboards and jumper wires
  • Git and ESP-IDF 5.1+

Software Requirements

  • ESP-IDF v5.1+ - Installation Guide
  • Git - For version control
  • HiveMQ Cloud Account - Free tier MQTT broker

Quick Start

1. Setup ESP-IDF

mkdir -p ~/esp
cd ~/esp
git clone --recursive https://github.com/espressif/esp-idf.git
cd esp-idf
./install.sh esp32
source export.sh

2. Clone Repository

cd ~
git clone https://github.com/vruga/esp_medmonitor.git
cd esp_medmonitor
git checkout shashvatt

3. Configure Credentials

cp node-a-gateway/main/config.h.template node-a-gateway/main/config.h
cp node-b-sentry/main/config.h.template node-b-sentry/main/config.h

# Edit with your WiFi and HiveMQ credentials
nano node-a-gateway/main/config.h
nano node-b-sentry/main/config.h

4. Build and Flash Node A

cd node-a-gateway
idf.py build
idf.py -p /dev/cu.usbserial-XXXXX flash monitor

5. Build and Flash Node B

cd ../node-b-sentry
idf.py build
idf.py -p /dev/cu.usbserial-YYYYY flash monitor

Pin Configuration

Node A GPIO Mapping

Component GPIO Protocol Purpose
MPU6050 SDA 21 I2C Accelerometer/Gyroscope data
MPU6050 SCL 22 I2C Accelerometer/Gyroscope clock
DHT11 Data 5 1-Wire Temperature & humidity
HW-827 ADC 36 ADC1_CH0 Heart rate sensor
Emergency Button 4 GPIO Input SOS button (active LOW)
UART TX 1 UART Serial output (115200 baud)
UART RX 3 UART Serial input

Node B GPIO Mapping

Component GPIO Protocol Purpose
RC522 MOSI 23 SPI RFID data in
RC522 MISO 25 SPI RFID data out
RC522 SCLK 19 SPI RFID clock
RC522 CS 22 SPI RFID chip select
IR Sensor 13 GPIO Input Motion detection
Buzzer 5 GPIO Output Alarm (NPN driver)
UART TX 1 UART Serial output
UART RX 3 UART Serial input

Features

Node A: Vital Monitoring

  • ✅ Fall Detection: Jerk-based algorithm (200 g/s threshold) with 2s cooldown
  • ✅ Posture Recognition: Complementary filter (99% gyro + 1% accel)
    • STANDING: pitch ≤ 15°
    • SITTING: pitch ≥ 20°
    • LYING: pitch & roll ≤ 10°
  • ✅ Heart Rate Monitoring: Peak detection on HW-827 sensor
  • ✅ Temperature Tracking: DHT11 with retry logic (WiFi interference tolerance)
  • ✅ Emergency Button: Manual SOS trigger
  • ✅ MQTT Publishing: Real-time sensor data to HiveMQ Cloud
  • ✅ ESP-NOW: Emergency messages to Node B (dynamic channel)

Node B: Access Control & Security

  • ✅ RFID Access Control: RC522 reader with full SPI protocol
    • Request → Anticollision → UID database lookup
    • Authorized/Unauthorized card detection
  • ✅ IR Motion Detection: PIR sensor with state machine
  • ✅ Security State Machine: IDLE → IR_DETECTED → AUTHORIZED/INTRUSION
  • ✅ Buzzer Alarm: GPIO-driven NPN transistor
  • ✅ MQTT Publishing: Security events to HiveMQ Cloud
  • ✅ ESP-NOW Receiver: Listens for emergencies from Node A

Network & Communication

  • ✅ WiFi: STA mode with auto-reconnect
  • ✅ MQTT over TLS: HiveMQ Cloud with certificate verification
  • ✅ SNTP: Time synchronization via pool.ntp.org
  • ✅ ESP-NOW: Dynamic channel detection (follows WiFi AP channel)
  • ✅ DHT11 Retry: Up to 3 retries on checksum errors

MISRA-C Compliance

Code follows MISRA-C:2012 guidelines:

  • ✅ Rule 8.4: Function prototypes in headers
  • ✅ Rule 14.4: All if-else chains have final else
  • ✅ Rule 17.7: All return values checked
  • ✅ Rule 10.3/10.4: Explicit type casts
  • ✅ Rule 2.7: Unused parameters marked (void)param
  • ✅ Rule 9.1: Variables initialized before use
  • ✅ Compiles with -Wall -Wextra -Werror

Testing

Quick Test Setup

# Terminal 1: Node A
cd node-a-gateway && idf.py -p /dev/cu.usbserial-A monitor

# Terminal 2: Node B
cd node-b-sentry && idf.py -p /dev/cu.usbserial-B monitor

Test Cases

  1. Fall Detection: Shake/drop Node A → Watch for "FALL DETECTED"
  2. Posture: Rotate Node A → Verify posture changes (STANDING/SITTING/LYING)
  3. Heart Rate: Simulate sensor pulses → Peak count increases
  4. RFID Authorized: Scan authorized card → Buzzer silent
  5. RFID Unauthorized: Scan unknown card → Buzzer sounds
  6. Emergency: Press button on Node A → Node B buzzer sounds
  7. MQTT: Check HiveMQ console for all messages

Troubleshooting

ESP32 won't flash

ls /dev/cu.usbserial-*
# Hold BOOT button while connecting

DHT11 timeouts

  • External 2.2kΩ pull-up required on GPIO 5
  • Keep wire short (<10cm)
  • Check 3.3V power

ESP-NOW not working

  • Both nodes must be on same WiFi channel
  • Verify MAC addresses match actual hardware
  • Both must be powered on WiFi

MQTT connection fails

  • Check WiFi SSID/password in config.h
  • Verify HiveMQ credentials
  • Ensure TLS certificate is correct

RFID not detected

  • Check SPI wiring (MOSI/MISO/SCLK)
  • Verify RC522 at 3.3V (not 5V)
  • Try increasing SPI clock if needed

Build Options

idf.py fullclean && idf.py build
idf.py -v build                    # Verbose output
idf.py build -j8                   # Parallel build
idf.py menuconfig                  # Configuration
idf.py monitor --timestamp         # Monitor with timestamps

Project Structure

esp_medmonitor/
├── node-a-gateway/          # Vital Monitor firmware
│   ├── main/
│   │   ├── config.h.template
│   │   ├── sensors/         # MPU6050, DHT11, HW-827
│   │   ├── tasks/           # Fall detection, sensor, MQTT
│   │   └── utils/
│   └── CMakeLists.txt
├── node-b-sentry/           # Access Control firmware
│   ├── main/
│   │   ├── config.h.template
│   │   ├── modules/         # RFID, IR, Buzzer
│   │   ├── tasks/           # Security, MQTT
│   │   └── utils/
│   └── CMakeLists.txt
├── Hackthon_PCB/            # KiCAD schematics & layouts
│   ├── Hackthon_PCB.kicad_sch
│   ├── Hackthon_PCB.kicad_pcb
│   ├── gerbers/
│   └── kicad_parts/
└── README.md

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IoT medical monitoring and access control system

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