How to Use sim800l: Examples, Pinouts, and Specs

The SIM800L is a compact GSM/GPRS module designed for communication over cellular networks. It supports a wide range of functionalities, including SMS, voice calls, and data transmission via GPRS. With its small size and low power consumption, the SIM800L is an excellent choice for IoT applications, remote monitoring, and embedded systems requiring cellular connectivity.

• Internet of Things (IoT) devices
• Remote monitoring and control systems
• GPS tracking and fleet management
• Home automation
• SMS-based alert systems
• Voice call-enabled embedded projects

• Operating Voltage: 3.4V to 4.4V (recommended: 4.0V)
• Power Consumption:
  • Idle: ~1mA
  • Active (GPRS): ~100mA to 250mA
  • Peak (transmission): ~2A
• Frequency Bands: Quad-band 850/900/1800/1900 MHz
• Communication Protocols: AT commands (3GPP TS 27.007, 27.005)
• Data Transmission: GPRS Class 12, up to 85.6 kbps
• SIM Card Support: Micro SIM
• Operating Temperature: -40°C to +85°C
• Dimensions: 25mm x 23mm x 3mm

The SIM800L module typically has 12 pins. Below is the pinout and description:

1. Power Supply:

   • The SIM800L requires a stable power supply of 4.0V. Use a step-down regulator (e.g., LM2596) or a LiPo battery to provide the required voltage.
   • Ensure the power supply can handle peak currents of up to 2A during transmission.

2. Connections:

   • Connect the VCC pin to the 4.0V power supply and GND to ground.
   • Connect the TXD pin of the SIM800L to the RX pin of your microcontroller.
   • Connect the RXD pin of the SIM800L to the TX pin of your microcontroller.
   • Optionally, connect the RST pin to a GPIO pin of your microcontroller for resetting the module.

3. Antenna:

   • Attach an external antenna to the SIM800L's antenna connector for better signal reception.

4. SIM Card:

   • Insert a micro SIM card into the SIM card slot. Ensure the SIM card is activated and has sufficient balance for SMS, calls, or data usage.

5. Communication:

   • Use AT commands to communicate with the SIM800L. These commands can be sent via UART from a microcontroller or a USB-to-TTL adapter connected to a PC.

• Use decoupling capacitors (e.g., 100µF and 10µF) near the power supply pins to stabilize the voltage.
• Avoid using the SIM800L with a 5V logic microcontroller directly. Use a voltage divider or level shifter to convert 5V signals to 3.3V.
• Ensure the antenna is securely connected to avoid poor signal quality.
• Place the module away from high-frequency noise sources to prevent interference.

Below is an example of how to send an SMS using the SIM800L and Arduino UNO:

• SIM800L VCC to a 4.0V power supply
• SIM800L GND to Arduino GND
• SIM800L TXD to Arduino pin 10 (RX)
• SIM800L RXD to Arduino pin 11 (TX)
• SIM800L RST to Arduino pin 9 (optional)

#include <SoftwareSerial.h>

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

void setup() {
  // Initialize serial communication
  Serial.begin(9600); // For debugging
  sim800l.begin(9600); // For SIM800L communication

  // Wait for the module to initialize
  delay(1000);
  Serial.println("Initializing SIM800L...");

  // Send AT command to check communication
  sim800l.println("AT");
  delay(1000);
  while (sim800l.available()) {
    Serial.write(sim800l.read());
  }

  // Send SMS
  sendSMS("+1234567890", "Hello from SIM800L!");
}

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

void sendSMS(String phoneNumber, String message) {
  sim800l.println("AT+CMGF=1"); // Set SMS mode to text
  delay(1000);

  sim800l.print("AT+CMGS=\"");
  sim800l.print(phoneNumber);
  sim800l.println("\"");
  delay(1000);

  sim800l.print(message); // Message content
  delay(1000);

  sim800l.write(26); // Send Ctrl+Z to send the SMS
  delay(5000);

  Serial.println("SMS sent!");
}

1. Module Not Responding to AT Commands:

   • Ensure the power supply is stable and provides sufficient current (up to 2A).
   • Check the RX and TX connections between the SIM800L and the microcontroller.
   • Verify the baud rate (default is 9600).

2. Poor Signal Quality:

   • Ensure the antenna is properly connected and positioned in an open area.
   • Check the SIM card for proper activation and network coverage.

3. Module Keeps Restarting:

   • This is often caused by an insufficient power supply. Use a power source capable of handling peak currents.

4. SMS Not Sending:

   • Ensure the SIM card has sufficient balance or an active SMS plan.
   • Verify the phone number format (e.g., include the country code).

• Can I use a 5V power supply for the SIM800L? No, the SIM800L requires a voltage between 3.4V and 4.4V. Using 5V can damage the module.

• What is the default baud rate of the SIM800L? The default baud rate is 9600, but it can be changed using AT commands.

• Can the SIM800L be used for internet access? Yes, the SIM800L supports GPRS for data transmission. You can use AT commands to configure and establish a GPRS connection.

• How do I reset the SIM800L? Pull the RST pin low for at least 100ms and then release it to reset the module.