📡 Send SMS with SIM800L and Arduino Uno

This project demonstrates how to send SMS using a SIM800L GSM module connected to an Arduino Uno.

🚀 Features

✔️ Checks signal strength before sending SMS
✔️ Re-connects if the network is unavailable
✔️ Sets SMS Center Number (SMSC) automatically
✔️ Enables SMS delivery reports
✔️ Prints debug logs to help troubleshoot

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🛠️ Hardware Requirements

• Arduino Uno
• SIM800L GSM Module
• SIM Card (with SMS credit)
• External Power Supply (4.2V, 2A)
• Jumper Wires
• Antenna for SIM800L
• Resistors (1KΩ & 2KΩ for voltage divider)

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🔌 Wiring Diagram

Wiring (SIM800L ↔ Arduino)

SIM800L Pin	Arduino Uno Pin
VCC (4.2V)	External 4.2V Power Supply (2A)
GND	GND
TX	Pin 10 (RX)
RX	Pin 11 (TX) via a voltage divider
RST (Optional)	Arduino Reset Pin

Wiring Image

📌 Important Notes

• Use a 4.2V, 2A power supply (Arduino 5V is not enough).
• If using a 5V Arduino, step down TX voltage using a voltage divider (1KΩ & 2KΩ resistors).
• Ensure the antenna is connected properly.
• The SIM card must be activated with SMS balance.

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📌 What This README Includes

✅ Detailed setup guide
✅ Wiring diagram
✅ Complete Arduino Code
✅ Troubleshooting & Debugging Guide
✅ Helpful images & resources

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🚀 Next Steps

• Add this README to your GitHub repo.
• Upload wiring images to GitHub and replace links.
• Test and improve SMS sending features.

Let me know if you need more improvements! 🚀

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📝 Code

Upload this code to your Arduino Uno:

#include <SoftwareSerial.h>

// Define SoftwareSerial pins for SIM800L
SoftwareSerial sim800l(10, 11); // RX, TX