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From: =?UTF-8?q?Fernando=20Mart=C3=ADnez=20Valenzuela?=
 <fer.martinez031206@gmail.com>
Date: Wed, 10 Jun 2026 09:35:54 -0600
Subject: [PATCH] =?UTF-8?q?Actualizaci=C3=B3n=20del=20README?=
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+# 🌡️ Raspberry Pi 4 Temperature & Humidity Monitoring System (HTU21D)
+
+---
+
+## 📌 Project Overview
+
+This project implements a real-time temperature and humidity monitoring system using a **Raspberry Pi 4** and an **HTU21D sensor**. The system reads environmental data via I2C, processes it using a C program, and displays the results on a web dashboard using Nginx.
+
+---
+
+## 🧠 System Architecture
+
+```
+HTU21D Sensor → I2C → C Program → JSON File → Nginx → Web Browser
+```
+
+---
+
+## 🧰 Materials
+
+### 🔧 Hardware
+
+* Raspberry Pi 4
+* HTU21D sensor
+* Jumper wires (female-to-female)
+* MicroSD card with Raspberry Pi OS
+* Power supply
+
+### 💻 Software
+
+* Raspberry Pi OS / Debian
+* GCC compiler
+* i2c-tools
+* libi2c-dev
+* Nginx
+* Git
+
+---
+
+## 🔌 Hardware Connections
+
+### 📷 Pin Reference Images
+
+Include these images in your repository:
+
+* `RaspberryPi4_PinMap.jpeg`
+* `TZCBIN8qL-HTU21D-Module-Pinout.png`
+
+---
+
+### 📍 Wiring Table
+
+| HTU21D | Raspberry Pi 4 |
+| ------ | -------------- |
+| VCC    | 3.3V           |
+| GND    | GND            |
+| SDA    | GPIO2 (SDA)    |
+| SCL    | GPIO3 (SCL)    |
+
+---
+
+## 🚀 Deployment Guide (From Scratch)
+
+### 📥 1. Clone the Repository
+
+```bash
+git clone http://<GITEA_SERVER>/<USER>/<REPOSITORY>.git
+# Downloads the project from the server
+
+cd <REPOSITORY>
+# Enters the project folder
+```
+
+---
+
+### 🧰 2. Install Dependencies
+
+```bash
+sudo apt update
+# Updates package list
+
+sudo apt install gcc i2c-tools libi2c-dev nginx git
+# Installs compiler, I2C tools, web server, and Git
+```
+
+---
+
+### ⚙️ 3. Enable I2C
+
+```bash
+sudo raspi-config
+# Opens Raspberry Pi configuration menu
+```
+
+Go to:
+
+```
+Interfacing Options → I2C → Enable
+```
+
+```bash
+sudo reboot
+# Restarts system to apply changes
+```
+
+---
+
+### 🔍 4. Verify Sensor
+
+```bash
+i2cdetect -y 1
+# Scans I2C bus for connected devices
+```
+
+Expected:
+
+```
+0x40
+```
+
+---
+
+### 🧑‍💻 5. Compile the Sensor Program
+
+```bash
+cd sensors/HTU21D
+# Move to sensor source code
+
+gcc main.c htu21d.c -o HTU21D -li2c
+# Compiles the program and links I2C library
+```
+
+---
+
+### 📂 6. Deploy Web Files
+
+```bash
+sudo cp -r ~/basic-ui-dashboard/* /var/www/html/
+# Copies project files to Nginx directory
+```
+
+```bash
+sudo mkdir -p /var/www/html/data
+# Creates folder for JSON output
+```
+
+---
+
+### 🔐 7. Set Permissions
+
+```bash
+sudo chmod +x /var/www/html/sensors/HTU21D/HTU21D
+# Allows execution of sensor program
+
+sudo chown -R www-data:www-data /var/www/html
+# Gives Nginx access to files
+```
+
+---
+
+### ▶️ 8. Run Sensor Loop
+
+```bash
+cd /var/www/html
+# Go to web directory
+
+while true; do ./sensors/HTU21D/HTU21D > data/HTU21D.json; sleep 5; done
+# Continuously updates JSON every 5 seconds
+```
+
+---
+
+### 🌐 9. Start Nginx
+
+```bash
+sudo systemctl start nginx
+# Starts web server
+
+sudo systemctl enable nginx
+# Enables auto-start on boot
+
+sudo systemctl status nginx
+# Verifies server is running
+```
+
+---
+
+### 🌍 10. Get Raspberry Pi IP
+
+```bash
+hostname -I
+# Displays local IP address
+```
+
+Example:
+
+```
+192.168.1.100
+```
+
+---
+
+### 🖥️ 11. Access from Another Computer
+
+Open a browser and go to:
+
+```
+http://192.168.1.100
+```
+
+---
+
+## 🔄 Real-Time Updates
+
+JavaScript fetch:
+
+```javascript
+fetch('./data/HTU21D.json?nocache=' + Date.now())
+```
+
+**What it does:**
+
+* Prevents browser cache
+* Forces fresh data request
+
+---
+
+## 🧪 How to Use
+
+1. Power on Raspberry Pi
+2. Connect sensor
+3. Run sensor loop
+4. Open browser
+5. Monitor values in real time
+
+---
+
+## ⚠️ Troubleshooting
+
+### ❌ No data update
+
+* Check loop is running
+* Verify `nocache` in fetch
+
+---
+
+### ❌ Permission denied
+
+```bash
+sudo nano /var/www/html/index.html
+# Edit file with admin privileges
+```
+
+---
+
+### ❌ Sensor not detected
+
+* Check wiring
+* Run `i2cdetect`
+
+---
+
+## 📈 Improvements
+
+* WebSockets (real-time without polling)
+* Database storage
+* Historical charts
+* Remote access via internet
+
+---
+
+## 🎯 Conclusion
+
+This project integrates:
+
+* Embedded systems (sensor + Raspberry Pi)
+* C programming
+* Linux system configuration
+* Web development (Nginx + JS)
+
+It demonstrates a complete pipeline from hardware acquisition to real-time web visualization.
+
+---