How to Use SIM800C: Examples, Pinouts, and Specs

The SIM800C is a compact and reliable GSM/GPRS module designed for communication over cellular networks. It supports a wide range of functionalities, including SMS, voice calls, and data transmission, making it a versatile choice for IoT applications, remote monitoring, and embedded systems. With its small form factor and low power consumption, the SIM800C is well-suited for battery-powered devices and space-constrained designs.

• Internet of Things (IoT) devices
• Remote monitoring and control systems
• GPS tracking and fleet management
• Home automation and smart appliances
• SMS-based alert systems
• Voice communication in embedded systems

The SIM800C module offers robust performance and a variety of features. Below are its key technical specifications:

The SIM800C module has multiple pins for power, communication, and control. Below is the pinout description:

1. Power Supply: Ensure a stable power supply of 3.7V to 4.2V. Use a capacitor (e.g., 100µF) near the VCC pin to handle current surges.
2. Antenna Connection: Connect a GSM antenna to the ANT pin for proper signal reception.
3. UART Communication: Connect the TXD and RXD pins to a microcontroller or USB-to-TTL converter for serial communication.
4. Network Status: Use the NETLIGHT pin to monitor the module's network status (e.g., blinking indicates searching or connected).
5. Reset: Use the RST pin to reset the module if needed (active low).

• Power Supply: The module can draw up to 2A during transmission bursts. Use a power supply capable of handling this load.
• Signal Quality: Place the antenna away from noise sources and ensure a strong GSM signal for reliable operation.
• Sleep Mode: Use the DTR pin to enable sleep mode for power-saving applications.
• UART Voltage Levels: Ensure the UART interface voltage levels match your microcontroller (e.g., use a level shifter if needed).

Below is an example of how to send an SMS using the SIM800C module with an Arduino UNO:

#include <SoftwareSerial.h>

// Define RX and TX pins for SoftwareSerial
SoftwareSerial sim800c(10, 11); // RX = Pin 10, TX = Pin 11

void setup() {
  // Initialize serial communication
  Serial.begin(9600); // For debugging
  sim800c.begin(9600); // For SIM800C communication

  // Wait for the module to initialize
  delay(1000);
  Serial.println("Initializing SIM800C...");

  // Send AT command to check communication
  sim800c.println("AT");
  delay(1000);
  while (sim800c.available()) {
    Serial.write(sim800c.read());
  }

  // Set SMS text mode
  sim800c.println("AT+CMGF=1"); // Set SMS to text mode
  delay(1000);

  // Send SMS
  sim800c.println("AT+CMGS=\"+1234567890\""); // Replace with recipient's number
  delay(1000);
  sim800c.println("Hello from SIM800C!"); // SMS content
  delay(1000);
  sim800c.write(26); // Send Ctrl+Z to send the SMS
  delay(5000);

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

void loop() {
  // No actions in loop
}

1. Module Not Responding to AT Commands

   • Ensure the power supply is stable and capable of providing sufficient current.
   • Check the UART connections (TXD and RXD) and ensure they are not swapped.
   • Verify the baud rate (default is 9600).

2. No Network Connection

   • Check the antenna connection and ensure it is securely attached.
   • Verify that the SIM card is properly inserted and has an active plan.
   • Ensure the module is in an area with good GSM signal strength.

3. SMS Not Sending

   • Confirm that the SIM card has sufficient balance or SMS credits.
   • Ensure the recipient's phone number is in the correct format (e.g., with country code).

4. Module Restarts During Operation

   • Check the power supply and ensure it can handle peak current demands (up to 2A).
   • Add a capacitor (e.g., 100µF) near the VCC pin to stabilize the power supply.

Q: Can the SIM800C work with 5V logic levels?
A: No, the SIM800C operates at 3.3V logic levels. Use a level shifter if interfacing with a 5V microcontroller.

Q: How do I reduce power consumption?
A: Enable sleep mode using the DTR pin and ensure the module is not actively transmitting when idle.

Q: What is the maximum baud rate supported?
A: The SIM800C supports baud rates up to 115200 bps, but 9600 bps is commonly used for stability.

Q: Can I use the SIM800C for GPS tracking?
A: No, the SIM800C does not have built-in GPS functionality. However, it can be paired with a GPS module for tracking applications.