I see you're experiencing a serious crash with a "Guru Meditation Error" (LoadProhibited). This is typically caused by memory access issues, often related to interrupt handling. Let's create a much simpler, more robust solution and explain how the YF-S201 sensor actually works.

Understanding the YF-S201 Flow Sensor

The YF-S201 is a hall-effect flow sensor that works on a simple principle:

1. Physical Operation:

   • Inside the sensor is a water turbine/impeller that rotates when water flows through it
   • A small magnet is attached to the turbine
   • A hall-effect sensor detects each rotation of the magnet

2. Pulse Generation:

   • Each rotation of the turbine generates electrical pulses
   • The standard YF-S201 generates approximately 450 pulses per liter

   • This can vary between 390-550 pulses per liter depending on:

     • Water pressure
     • Flow rate
     • Installation orientation
     • Manufacturing variations

3. Measurement Approach:

   • The most reliable way to measure flow is to simply count pulses
   • Total volume = Total pulses ÷ Pulses per liter
   • Flow rate = Pulses in time period ÷ Pulses per liter ÷ Time period

Why Previous Code Was Crashing

The previous code was likely crashing due to:

1. Complex Interrupt Handler:

   • The interrupt handler was doing too much calculation
   • Interrupt handlers should be kept as simple as possible

2. Volatile Variable Issues:

   • Improper handling of volatile variables between interrupt context and main loop
   • Potential race conditions

3. Division by Zero:

   • The pulse duration approach can lead to division by zero or very small numbers
   • This happens when flow starts/stops or is irregular

Key Improvements in This Code

1. Simplified Approach:

   • Uses the most reliable method: simple pulse counting
   • Minimal processing in the interrupt handler
   • Safe copying of volatile variables

2. Accurate Calibration:

   • Uses 450 pulses per liter as the starting point (manufacturer standard)
   • You can adjust this value based on your observations

3. Robust Error Prevention:

   • No complex math in interrupt handlers
   • No division by zero possibilities
   • Non-blocking code to prevent watchdog timer issues

How to Calibrate

For accurate measurements, you should calibrate the sensor:

1. Run a known volume of water through the sensor (e.g., 1 liter measured with a measuring cup)
2. Note the number of pulses counted
3. Update the PULSES_PER_LITER value in the code

For example, if you run exactly 1 liter through and get 430 pulses:

This simplified approach should be much more reliable and still provide accurate measurements. The code focuses on stability first, then accuracy, which is essential for embedded systems.

Complete Water Monitoring System with Server Integration and Flutter App

I'll create a comprehensive solution that includes:

1. ESP32 code to collect and send water flow data to a server
2. Database structure for storing the data
3. Flutter application to visualize and manage the data

Part 1: ESP32 Water Flow Monitor with Server Integration

Complete Water Monitoring System Overview

I've created a comprehensive solution for your water monitoring system that includes:

1. ESP32 Water Flow Monitor with Server Integration

   • Collects accurate flow data using the YF-S201 sensor
   • Sends data to a server via WiFi
   • Includes leak detection and hourly consumption tracking
   • Uses the calibration factor of 390 pulses per liter that you specified

2. Database Schema

   • Complete SQL database structure for storing water consumption data
   • Tables for devices, readings, hourly/daily/monthly consumption
   • Support for alerts, maintenance records, and user management
   • Optimized with indexes for performance

3. Flutter Mobile Application

   • User-friendly interface for monitoring water consumption
   • Real-time flow rate and status monitoring
   • Historical data visualization with charts
   • Alerts for potential leaks and unusual consumption
   • Settings for device management and user preferences

Key Features for Water Service Providers

1. Consumption Monitoring

   • Real-time flow rate monitoring
   • Hourly, daily, and monthly consumption tracking
   • Historical data analysis and visualization

2. Leak Detection

   • Automatic detection of continuous flow
   • Alerts for potential leaks
   • Notification system for immediate action

3. Billing Integration

   • Monthly consumption tracking for billing purposes
   • Historical consumption data for billing verification
   • Support for different billing rates and periods

4. Maintenance Management

   • Device status monitoring
   • Maintenance scheduling and tracking
   • Technician assignment and reporting

5. Customer Management

   • User accounts for customers
   • Device assignment to specific users
   • Customer usage reporting

Implementation Steps

1. ESP32 Setup

   • Upload the provided code to your ESP32
   • Update the WiFi credentials and server URL
   • Ensure the device ID is unique for each water meter

2. Server Setup

   • Set up a database using the provided schema
   • Create API endpoints to receive data from ESP32 devices
   • Implement authentication for secure data transmission

3. Flutter App Development

   • Use the provided code as a foundation
   • Connect to your server API for real data
   • Customize the UI to match your branding

This solution provides a complete end-to-end system for water monitoring that would be valuable for water service providers. The system is scalable and can be extended with additional features as needed.