GPS Accident Detection System - ESP8266

A comprehensive IoT-based vehicle accident detection system that monitors vehicle movements, detects accidents using MPU6050 sensor, provides GPS location tracking, and sends emergency alerts via MQTT and SMS.

Overview

This system uses an ESP8266 microcontroller to monitor vehicle movements in real-time. It detects accidents through impact analysis and rollover detection using an MPU6050 accelerometer/gyroscope, tracks location via GPS, and automatically sends emergency notifications through MQTT and SMS alerts.

System Evolution

The project evolved from a monolithic prototype → a modular sketch (v0.0.5) → a PlatformIO Clean Architecture project. The latest overhaul organizes the firmware into four layers with dependencies pointing inward only (Presentation → Application → Domain, and Infrastructure → Domain; the Domain layer depends on nothing), delivering higher reliability, testable business logic, and hardware that can be swapped without touching the core.

Architecture

The firmware is organized into four layers under src/:

src/
├── domain/                         # Enterprise rules — no hardware, no libs
│   ├── entities/
│   │   ├── AccidentEvent.h         # (hardware-free, host-testable)
│   │   ├── GpsLocation.h
│   │   ├── DeviceInfo.h
│   │   └── SystemTypes.h           # WiFiStatus, OTAContext
│   └── interfaces/                 # Pure abstractions (ports)
│       ├── IGpsProvider.h
│       ├── IGsmAlertSender.h
│       ├── IMqttTransport.h
│       ├── IAccidentDetector.h
│       ├── IConfigRepository.h
│       └── IClock.h
│
├── application/                    # Use cases — depends only on interfaces
│   ├── AccidentAlgorithm.{h,cpp}   # Pure STA/LTA + rollover math (host-tested)
│   └── services/
│       └── AccidentService.{h,cpp} # Orchestrates detect → alert → publish
│
├── infrastructure/                 # Adapters — concrete impls of the ports
│   ├── gps/TinyGpsPlusProvider.{h,cpp}
│   ├── gsm/Sim800lAlertSender.{h,cpp}
│   ├── mqtt/PubSubClientTransport.{h,cpp}
│   ├── sensors/Mpu6050Detector.{h,cpp}
│   ├── persistence/LittleFsConfigRepository.{h,cpp}
│   └── system/{EspClock,EspSysUtils}.{h,cpp}
│
└── main.cpp                        # Presentation / composition root

include/config.h                    # Shared pins & constants (global)
test/test_accident_algorithm/       # Native unit tests (no hardware)
data/config.json                    # Default LittleFS config (uploadfs)
legacy/                             # Original flat sketch (kept, NOT compiled)

Key ideas

Dependency inversion. AccidentService and Mpu6050Detector never name a concrete class; they receive IGpsProvider, IGsmAlertSender, IMqttTransport, IConfigRepository and IClock through their constructors. Only main.cpp (the composition root) wires the concrete implementations together.
Swappable adapters. Changing the GPS chip (NEO-6M → NEO-8M) or the GSM modem (SIM800L → SIM7600) means writing one new class in infrastructure/ and changing one line in main.cpp — no business-logic changes.
Testable core. AccidentAlgorithm was split out of the MPU6050 driver so the impact/rollover logic runs on the host with no hardware. See test/test_accident_algorithm/.

Legacy module mapping

The original flat modules were reorganized into the layers above (the old files remain under legacy/ for reference and are not compiled):

Legacy file	Now lives in
`GPS.ino`	`src/main.cpp` (composition root)
`Types.h`	`src/domain/entities/*` + `SystemTypes.h`
`config.h`	`include/config.h`
`AccidentMonitor.*`	`src/infrastructure/sensors/Mpu6050Detector.` + `src/application/AccidentAlgorithm.`
`GpsModule.*`	`src/infrastructure/gps/TinyGpsPlusProvider.*`
`GsmModule.*`	`src/infrastructure/gsm/Sim800lAlertSender.*`
`MqttClientModule.*`	`src/infrastructure/mqtt/PubSubClientTransport.*`
`DeviceConfig.*`	`src/infrastructure/persistence/LittleFsConfigRepository.*`
`SysUtils.*`	`src/infrastructure/system/EspClock.` + `EspSysUtils.`

Features

Core Functionality

Real-time Accident Detection: Impact and rollover detection using MPU6050
GPS Tracking: Location monitoring with TinyGPSPlus
Dual Alert System: MQTT notifications + SMS emergency alerts
Wireless Connectivity: WiFi with automatic reconnection
Secure Communication: MQTTS with SSL/TLS encryption
Over-the-Air Updates: Remote firmware updates via MQTT
Multiple Configuration Methods: Serial, SMS, MQTT, and Web Interface

Technical Features

Modular C++ Design (OOD): Decoupled hardware managers for high scalability.
Configurable Sensitivity: Adjustable impact sensitivity and rollover angles.
Buzzer Alerts: Audible notifications for accidents.
LED Status Indicators: Visual WiFi connection status.
LittleFS JSON Configuration: Persistent settings stored as JSON (modern alternative to EEPROM).
NTP Time Synchronization: Accurate timestamping for event logs.
GSM Module Support: SIM800L with automated command processing.
Multi-protocol Command Interface: Serial, SMS, and MQTT configuration callbacks.

Hardware Requirements

Microcontroller

ESP8266 NodeMCU (ESP-12E/ESP-12S)

Sensors & Modules

MPU6050: Accelerometer and gyroscope for motion detection
GPS Module: NEO-6M or compatible for location tracking
GSM Module: SIM800L for SMS alerts
Buzzer: Piezo buzzer for audible alerts
LED: Status indicator LED
Button: Physical button for configuration

Pin Configuration

Component	GPIO Pin	NodeMCU Pin	Function
Button	GPIO0	D3	Configuration/Reset
WiFi LED	GPIO2	D4	Status indicator
Buzzer	GPIO15	D8	Audible alerts
GSM RX	GPIO13	D7	SIM800L RX
GSM TX	GPIO12	D6	SIM800L TX
GPS RX	GPIO14	D5	GPS Module RX
GPS TX	GPIO16	D0	GPS Module TX
I2C SDA	GPIO4	D2	MPU6050 SDA
I2C SCL	GPIO5	D1	MPU6050 SCL

Installation

This is a PlatformIO project. Use the PlatformIO IDE extension (VS Code) or the pio CLI. Dependencies are declared in platformio.ini and fetched automatically — no manual library installation needed.

Prerequisites

PlatformIO Core (CLI) or the PlatformIO IDE extension for VS Code
Library dependencies (auto-installed from platformio.ini):
- mikalhart/TinyGPSPlus
- knolleary/PubSubClient
- bblanchon/ArduinoJson (v6)
- electroniccats/MPU6050
SoftwareSerial, ESP8266WiFi, WiFiClientSecure, ArduinoOTA, LittleFS and EEPROM ship with the ESP8266 Arduino core and are not listed in lib_deps.

Setup Steps

Clone the repository and open the GPS folder in VS Code (PlatformIO) or a terminal.
Configure hardware connections (see Pin Configuration).
Update settings in include/config.h (WiFi certificate, MQTT server, pins).
Build, upload the filesystem, and flash the firmware (commands below).

Build & test

pio run                 # build firmware for nodemcuv2 (ESP8266)
pio run -t upload       # flash firmware
pio run -t uploadfs     # upload data/ (config.json) to LittleFS
pio test -e native      # run host unit tests for AccidentAlgorithm (needs a host GCC — MinGW-w64 on Windows, or WSL)
pio device monitor      # serial monitor @ 115200

Notes / deviations from the original sketch

MQTT_TOPIC_CONFIG was referenced but never defined in the original config.h (the sketch would not compile as-is). It is now defined in include/config.h as the PROGMEM "config" topic — adjust if needed.
The original loop() passed an always-empty GPSData to the SMS alert, so alerts never carried a location. AccidentService::process() now reads the live fix from IGpsProvider before alerting. This is a behavior change (an intentional bug fix); revert inside AccidentService.cpp if undesired.
Serial/OTA command handling beyond the STATUS SMS was not present in the original loop() and was not invented here. The command set documented below is a natural follow-up to wire into a dedicated CommandRouter.

Configuration Commands

The system includes multiple ways to configure accident detection parameters:

1. Serial Port Commands (Serial Monitor)

Connect to the serial port (115200 baud) and use the following commands:

Basic Configuration

set phone +18291234567         # Change emergency phone number
set sensitivity 2500           # Change sensitivity (500-10000)
set angle 60                   # Change rollover angle (10-90°)
set delay 30000                # Change alert delay (1000-600000ms)
set sms on                     # Enable/disable SMS alerts (on/off)
save                           # Save configuration to EEPROM

System Commands

help or ?                      # Show command menu
config or show                 # Show current configuration
status                         # Publish status via MQTT
location                       # Get and publish GPS location
test_sms                       # Send test SMS
sms_test                       # Send SMS test to configured number

Diagnostics

wifi                           # Show WiFi information
mqtt                           # Show/connect MQTT status
gsm                            # Check GSM module
gps                            # Show GPS information
gps_debug                      # Complete GPS diagnostic
gps_raw                        # Show RAW GPS data for 5 seconds
reset                          # Restart device

2. SMS Commands

Send SMS to the configured emergency phone number:

Available SMS Commands

HELP or AYUDA or ?             # Show command menu
STATUS or ESTADO               # System status
LOCATION or UBICACION or LOC   # Current GPS location
CONFIG or CONFIGURACION        # Current configuration
TEST or TEST_SMS               # Test SMS to emergency number

SMS Configuration Commands

SET PHONE [number]             # Change emergency phone number
SET SENS [value]               # Change sensitivity (500-10000)
SET ANGLE [degrees]            # Change rollover angle (10-90)
SET DELAY [ms]                 # Change alert delay (1000-600000)
SET SMS [ON/OFF]               # Enable/disable SMS
SAVE or GUARDAR                # Save configuration

System SMS Commands

WIFI or WIFI INFO              # WiFi information
GPS                            # GPS status
GSM                            # GSM module status
MQTT                           # MQTT status
RESET or REINICIAR             # Restart device

3. MQTT Commands

Direct Commands

Send to topic commands/{device_id}:

reset: Restart the device
status: Request status report
location: Request immediate GPS location
get_config: Get current configuration

JSON Configuration via MQTT

Send JSON to topic config:

{
  "sensitivity": 2500,
  "rollover_angle": 60,
  "alert_delay": 30000,
  "sms_enabled": true,
  "emergency_phone": "+18291234567"
}

4. Web Interface Configuration (WiFiManager)

Activate AP mode: Press and hold the physical button for 3+ seconds
Connect: WiFi SSID: VESIS-{CHIP_ID}, Password: 12345678
Configure: Enter your WiFi SSID and password
Restart: The device will restart automatically

Default Values and Ranges

Parameter	Default Value	Acceptable Range
Sensitivity	2000	500 - 10000
Rollover Angle	60°	10° - 90°
Alert Delay	30000ms	1000 - 600000ms
Emergency Phone	-	Minimum 10 digits
SMS Enabled	true	true/false

Configuration Examples

Example 1: Basic Serial Configuration

set phone +18295551234
set sensitivity 3000
set angle 70
set delay 15000
set sms on
save

Example 2: SMS Configuration

SET PHONE +18295556789
SET SENS 4000
SET ANGLE 65
SET DELAY 20000
SET SMS ON
SAVE

Example 3: SMS Verification

HELP         # View all commands
STATUS       # View current status
CONFIG       # View configuration
LOCATION     # Get location

Configuration Persistence

LittleFS Storage (v0.0.5): Configuration is now stored in a config.json file. This provides atomic writes and human-readable settings via the file system.
EEPROM Migration: The system has transitioned from raw EEPROM addresses to the LittleFS filesystem for improved reliability and data integrity.
Auto-Load: Current settings are automatically loaded from /config.json on startup.
Validation: Strict range validation is performed before any change is persisted.
Data Upload: Remember to upload the data folder using the ESP8266 LittleFS Data Upload tool before the first run.

Important Notes

Modular Architecture: Commands are now handled via a clean callback system (onSmsReceived, onMqttEvent), making the system highly extensible.
SMS Authorization: Only the configured emergency number can send SMS commands.
Phone Format: Numbers must have at least 10 digits and can include +, spaces, and dashes.
Restart Required: Certain changes require a restart to be fully applied to hardware modules.
Confirmation: Successful configuration changes trigger confirmations via MQTT/SMS/Serial.

Advanced Diagnostic Commands

gps_debug     # Complete GPS diagnostic
gps_raw       # View raw NMEA data
gps           # Current GPS status
gsm           # Verify GSM module

These commands provide detailed information for troubleshooting hardware and connectivity issues.

Accident Detection Settings

struct AccidentConfig {
  int sensitivity = 2000;        // Impact sensitivity threshold
  int rollover_angle = 60;       // Rollover detection angle
  unsigned long alert_delay = 30000; // Alert delay in milliseconds
  String emergency_phone = "+18290000000"; // Emergency contact number
  bool sms_enabled = true;       // Enable/disable SMS alerts
};

MQTT Configuration

const char* MQTT_SERVER = "example.com";
const int MQTT_PORT = 8084;
const char* API_KEY = "EXAMPLE_API_KEY";

MQTT Topics

Communication Channels

Topic	Direction	Purpose
`telemetry`	Outgoing	GPS location data
`events`	Outgoing	System events and accident alerts
`commands`	Incoming	Device control commands
`ota`	Incoming	Firmware update commands
`status`	Outgoing	Device status information
`config`	Bidirectional	Configuration management

API Reference

Command Processing

The system responds to various MQTT commands:

System Commands

reset: Restart the device
status: Request current status report
location: Request immediate GPS location
get_config: Retrieve current configuration

Configuration Commands

Send JSON to config topic:

{
  "sensitivity": 2000,
  "rollover_angle": 60,
  "alert_delay": 30000,
  "sms_enabled": true,
  "emergency_phone": "+1234567890"
}

Event Publishing

The system publishes structured JSON events:

Accident Event Example

{
  "Device": {
    "status": "connected",
    "ChipId": "ABC123",
    "MacAddress": "AA:BB:CC:DD:EE:FF",
    "IPAddress": "192.168.1.100",
    "ChipType": "ESP8266",
    "FirmwareVersion": "v0.0.4"
  },
  "Timestamp": "2024-01-15T10:30:45.123Z",
  "Details": {
    "chipId": "ABC123",
    "accident": {
      "impact_detected": true,
      "rollover_detected": false,
      "impact_magnitude": 2450.5,
      "roll_angle": 15.2,
      "pitch_angle": 5.8,
      "gps_data": {
        "latitude": 40.7128,
        "longitude": -74.0060,
        "is_valid": true
      },
      "config": {
        "sensitivity": 2000,
        "rollover_angle": 60,
        "alert_delay": 30000,
        "sms_enabled": true
      }
    }
  }
}

OTA Updates

Firmware Update Process

The system supports chunked OTA updates via MQTT:

Update Initiation

{
  "EventType": "UpdateFirmwareDevice",
  "Details": {
    "FirmwareVersion": "v1.0.0",
    "Base64Part": "[base64_encoded_data]",
    "PartIndex": 1,
    "TotalParts": 10,
    "TotalSize": 500000
  }
}

Update Progress Tracking

Progress Updates: Published every 25% completion
Error Handling: Automatic rollback on failure
Memory Management: Optimized for ESP8266 constraints
Timeout Protection: 7-minute update timeout

OTA Features

Chunked Transfer: Handles large firmware files in parts
Base64 Encoding: Secure data transmission
Progress Reporting: Real-time update status
Error Recovery: Automatic cleanup on failure
Version Validation: Prevents downgrade attacks

Common Issues

WiFi Connection Problems

Symptoms: Rapid LED blinking, no MQTT connection
Solutions:
- Check WiFi credentials
- Use physical button to enter AP mode
- Verify signal strength

GPS Not Working

Symptoms: Invalid location data, no satellite lock
Solutions:
- Check antenna connection
- Ensure outdoor placement
- Verify baud rate (9600)

MQTT Connection Issues

Symptoms: No message publishing/subscription
Solutions:
- Verify MQTT server credentials
- Check SSL certificate configuration
- Confirm network connectivity

Accident Detection False Positives

Solutions:
- Adjust sensitivity in configuration
- Modify vibration damping parameters
- Calibrate MPU6050 sensor

Command Interface Issues

If commands don't work:

Verify MQTT/WiFi/GPS connection
Confirm SMS number is correctly configured
Check syntax (uppercase/lowercase)
Verify available memory (status command)
Check serial logs for specific errors

Debug Mode

Enable debug output by defining ENABLE_DEBUG in include/config.h:

#define ENABLE_DEBUG

Status Indicators

LED Pattern	Status
Solid ON	WiFi connected
Slow Blink	WiFi connecting
Fast Blink	WiFi disconnected
Buzzer Sound	Accident detected

Troubleshooting

For issues and questions:

Check the troubleshooting section
Verify hardware connections
Ensure proper power supply
Review MQTT broker configuration
Use diagnostic commands for detailed debugging

Backend Implementation

To use MQTTOTA in your project, you'll need an MQTT server to manage OTA updates. You can implement your own backend using our reference repository:

MQTT Broker for OTA Updates

Repository: github.com/Ruben890/Mqtt-Broker
Description: Complete backend for managing OTA updates via MQTT/MQTTS
Features:
- Configurable MQTT server
- IoT device management
- Firmware update delivery
- OTA progress tracking
- Error handling and retry mechanisms

Steps to use the backend:

Clone the backend repository
Configure the MQTT broker according to your needs
Implement the update delivery logic
Connect your ESP32 devices to the broker
Manage OTA updates from a centralized interface

Example workflow:

// From your backend
1. Prepare firmware in base64 format
2. Publish MQTT message to target device
3. Monitor progress via callbacks
4. Confirm successful completion
5. Log results in database

The backend provides a scalable architecture for managing multiple devices simultaneously, with support for mass updates and firmware version management.

Broker Compatibility

Tested with:

Mosquitto 2.0+
EMQX 5.0+
HiveMQ Cloud
AWS IoT Core
ESP-IDF MQTT client (used in BasicOTA example)

License

Licensed under the MIT License. See LICENSE for details.

Contact

Author: Jorge Gaspar Beltre Rivera
Project: GPS Accident Detection System - ESP8266

Support

This project is developed independently. Even a small contribution helps me dedicate more time to development, testing, and releasing new features.

Name		Name	Last commit message	Last commit date
.vscode		.vscode
data		data
include		include
legacy		legacy
src		src
test/test_accident_algorithm		test/test_accident_algorithm
.gitignore		.gitignore
LICENSE		LICENSE
Readme.md		Readme.md
compile_commands.json		compile_commands.json
platformio.ini		platformio.ini

Latest commit

History

Folders and files

Repository files navigation

GPS Accident Detection System - ESP8266

Table of Contents

Overview

System Evolution

Architecture

Key ideas

Legacy module mapping

Features

Core Functionality

Technical Features

Hardware Requirements

Microcontroller

Sensors & Modules

Pin Configuration

Installation

Prerequisites

Setup Steps

Build & test

Notes / deviations from the original sketch

Configuration Commands

1. Serial Port Commands (Serial Monitor)

Basic Configuration

System Commands

Diagnostics

2. SMS Commands

Available SMS Commands

SMS Configuration Commands

System SMS Commands

3. MQTT Commands

Direct Commands

JSON Configuration via MQTT

4. Web Interface Configuration (WiFiManager)

Default Values and Ranges

Configuration Examples

Example 1: Basic Serial Configuration

Example 2: SMS Configuration

Example 3: SMS Verification

Configuration Persistence

Important Notes

Advanced Diagnostic Commands

Accident Detection Settings

MQTT Configuration

MQTT Topics

Communication Channels

API Reference

Command Processing

System Commands

Configuration Commands

Event Publishing

Accident Event Example

OTA Updates

Firmware Update Process

Update Initiation

Update Progress Tracking

OTA Features

Common Issues

WiFi Connection Problems

GPS Not Working

MQTT Connection Issues

Accident Detection False Positives

Command Interface Issues

Debug Mode

Status Indicators

Troubleshooting

Backend Implementation

Broker Compatibility

License

Contact

Support

About

Resources

Stars

Watchers

Forks

Releases

Packages