The SIM800L GPRS GSM Module with Micro SIM Card is a highly versatile communication module designed for global connectivity and integration into a range of electronic projects. Supporting quad-band frequencies (GSM850, EGSM900, DCS1800, PCS1900), it ensures seamless connection to any global GSM network with a 2G SIM. This module enables various functions, including making and receiving voice calls using an external 8Ω speaker and electret microphone, sending and receiving SMS messages, and transmitting GPRS data (TCP/IP, HTTP). Additionally, it can scan and receive FM radio broadcasts. With a transmit power of Class 4 (2W) for GSM850 and Class 1 (1W) for DCS1800, it delivers robust performance. It uses a serial-based AT command set for control and features FL connectors for cell antennas, supporting Micro SIM cards.

Specifications

• Model: SIM800L
• Chip: Original SIM800L Chip
• SIM Type: Micro SIM Card
• Frequency Bands:
  • GSM850
  • EGSM900
  • DCS1800
  • PCS1900
• GPRS:
  • Class 12
• Power Supply:
  • Operating Voltage: 3.4V to 4.4V (Typically 4V)
  • Current Consumption: Up to 2A (peak transmission mode)
• Transmit Power:
  • Class 4: 2W for GSM850
  • Class 1: 1W for DCS1800
• Interface:
  • UART (Serial Communication)
  • Supports AT commands
• Data Rate:
  • GSM: Up to 85.6 kbps
  • GPRS: Up to 85.6 kbps
• Temperature Range:
  • Operating Temperature: -40°C to +85°C
• Dimensions: Approximately 25mm x 23mm x 3mm
• Antenna: External GSM antenna (included or available separately)
• Additional Features:
  • Voice call capabilities
  • SMS functionality
  • GPRS data transmission (TCP/IP, HTTP)
  • FM radio scanning and reception
  • Serial-based AT command set
  • FL connectors for cell antennas

How to interface with an Arduino?

To interface a SIM800L GSM/GPRS module with an Arduino UNO, follow these steps:

1. Hardware Connections

Pin Connections:

1. Power Supply:

   • SIM800L VCC: Connect to a stable 4.2V to 5V power supply. The SIM800L module can draw up to 2A during transmission, so it's best to use an external power source like a 5V regulated power supply or battery.
   • GND: Connect to Arduino GND.

2. Serial Communication:

   • SIM800L TX (Transmit): Connect to Arduino RX (Digital Pin 0).
   • SIM800L RX (Receive): Connect to Arduino TX (Digital Pin 1). Note that the SIM800L operates at 2.8V logic levels, so you might need a level shifter or a voltage divider to drop the Arduino's 5V TX signal to 2.8V.

3. Additional Pins:

   • RST (Reset): Connect to an Arduino digital pin if you want to control the module's reset function.
   • KEY (Key): Connect to 3.3V to enable the module if necessary.

2. Code Example

Here’s a basic example to send an SMS using the SIM800L module:

#include <SoftwareSerial.h>

// Create a software serial port to communicate with the SIM800L module
SoftwareSerial sim800(7, 8); // RX, TX

void setup() {
  // Start serial communication with the PC
  Serial.begin(9600);
  // Start serial communication with the SIM800L module
  sim800.begin(9600);
  
  // Give some time for the module to initialize
  delay(1000);

  // Send an SMS
  sendSMS("Your message here", "+1234567890"); // Replace with your message and recipient number
}

void loop() {
  // Nothing to do here
}

void sendSMS(String message, String number) {
  // Set SMS mode to text
  sim800.println("AT+CMGF=1");
  delay(500);

  // Set the recipient number
  sim800.print("AT+CMGS=\"");
  sim800.print(number);
  sim800.println("\"");
  delay(500);

  // Send the message
  sim800.println(message);
  delay(500);

  // End the message with Ctrl+Z
  sim800.write(26);
  delay(500);
  
  // Print confirmation to the serial monitor
  Serial.println("SMS sent");
}

3. Testing

• Power Up: Connect the power supply to the SIM800L module.
• Upload Code: Upload the code to the Arduino UNO.
• Monitor Output: Open the Serial Monitor in the Arduino IDE to see debug messages. The module should send an SMS to the specified number.

4. Troubleshooting

• No Response: Ensure the module has adequate power. Verify that the connections are correct and the baud rate matches.
• SMS Not Sent: Check if the SIM card is properly inserted and has SMS capabilities. Ensure the network signal is strong enough.

5. Additional Tips

• Power Supply: Use a stable and sufficient power supply for the SIM800L. It’s a good practice to decouple the power supply with capacitors if you experience instability.
• AT Commands: Familiarize yourself with AT commands for more advanced functionalities, such as making calls or checking network status.