🚀 ESP32 WiFi Auto-Connect OTA

A clean Arduino OTA firmware starter for ESP32-S3 and ESP32-C6 boards. The sketch connects to your router Wi-Fi on boot, automatically falls back to its own setup access point when the router is unavailable, and starts Arduino OTA so future firmware uploads can happen wirelessly.

✨ Features

• 📡 Connects to a hardcoded router Wi-Fi network at startup.
• 🛟 Starts a fallback OTA Wi-Fi access point if router connection times out.
• 🔁 Keeps router Wi-Fi connected and retries after disconnects.
• 🧭 Prints OTA hostname, password, and board IP address to Serial Monitor.
• 📲 Supports wireless firmware uploads with Arduino OTA tooling.
• 🧱 Plain C-style Arduino sketch structure: macros and functions, no classes or lambdas.

🧰 Tech Stack

Layer	Technology
Microcontroller	ESP32-S3 / ESP32-C6
Framework	Arduino ESP32 Core
Language	Arduino C/C++
Connectivity	Wi-Fi station mode + fallback access point mode
OTA	ArduinoOTA
Debugging	USB Serial Monitor at 115200 baud

📁 Project Structure

.
├── README.md
└── WiFiAutoConnectOTA/
    └── WiFiAutoConnectOTA.ino

Arduino expects the .ino filename to match its containing folder name, so the sketch lives in WiFiAutoConnectOTA/WiFiAutoConnectOTA.ino.

🚦 Getting Started

1. Install Requirements

• Arduino IDE or another ESP32 Arduino-compatible build/upload tool.
• Arduino ESP32 core with support for your selected ESP32-S3 or ESP32-C6 board.
• USB cable for the first flash.
• Wi-Fi credentials for your router.

2. Configure the Sketch

Open WiFiAutoConnectOTA/WiFiAutoConnectOTA.ino and update these values:

#define WIFI_SSID       "YOUR_ROUTER_WIFI_SSID"
#define WIFI_PASSWORD   "YOUR_ROUTER_WIFI_PASSWORD"

#define OTA_HOSTNAME    "esp32-ota-board"
#define OTA_PASSWORD    "12345678"

#define OTA_AP_SSID     "ESP32-OTA-SETUP"
#define OTA_AP_PASSWORD "87654321"

Recommended changes before deployment:

• Replace WIFI_SSID and WIFI_PASSWORD with your router credentials.
• Change OTA_PASSWORD to a strong password.
• Change OTA_AP_PASSWORD to a strong password of at least 8 characters.
• Optionally customize OTA_HOSTNAME to identify the board on your network.

3. First Upload Over USB

1. Connect the ESP32-S3 or ESP32-C6 over USB.
2. Select the correct board and port in Arduino IDE.
3. Open the sketch folder.
4. Upload normally over USB/serial.
5. Open Serial Monitor at 115200 baud.

4. Upload Updates Over Wi-Fi

After the first USB upload:

1. Keep the board powered on.
2. Make sure your computer is on the same Wi-Fi network as the board, or connect to the fallback AP if router Wi-Fi is unavailable.
3. Select the network OTA port in Arduino IDE.
4. Upload your changed firmware wirelessly.
5. Enter the configured OTA password when prompted.

📶 Network Behavior

Router Mode

On boot, the board tries to connect to WIFI_SSID for up to WIFI_CONNECT_TIMEOUT_MS milliseconds. If successful, the Serial Monitor prints the board IP address and OTA connection details.

Fallback AP Mode

If router Wi-Fi is unavailable, the board starts a fallback access point using OTA_AP_SSID and OTA_AP_PASSWORD. Connect your computer to that AP, then upload over OTA directly to the board.

Reconnect Handling

When running in router mode, the loop checks for Wi-Fi disconnects and retries after WIFI_RECONNECT_PAUSE_MS milliseconds.

⚙️ Tunable Constants

Constant	Default	Purpose
SERIAL_BAUD_RATE	115200	Serial Monitor speed
WIFI_CONNECT_TIMEOUT_MS	30000	Router connection timeout
WIFI_RETRY_DELAY_MS	500	Delay between Wi-Fi connection dots
WIFI_RECONNECT_PAUSE_MS	5000	Delay between reconnect attempts
STATUS_PRINT_INTERVAL_MS	10000	Periodic OTA status logging interval

🔐 Security Notes

• Do not leave the example OTA password in production firmware.
• Do not commit real router credentials to a public repository.
• Use a unique fallback AP SSID and strong AP password.
• Disable fallback AP behavior if the device will be deployed in an untrusted area.

🧪 Troubleshooting

Problem	What to Check
Board does not appear as an OTA port	Confirm the first USB flash succeeded and your computer is on the same network.
OTA password rejected	Confirm OTA_PASSWORD matches the password entered by the uploader.
Router connection times out	Check WIFI_SSID, WIFI_PASSWORD, signal strength, and 2.4 GHz compatibility.
Fallback AP does not start	Ensure OTA_AP_PASSWORD is at least 8 characters.
ESP32-C6 build fails	Update to an Arduino ESP32 core version that supports your board.