How to Use GSM SIM808: Examples, Pinouts, and Specs

The GSM SIM808 module is a compact and versatile board that integrates GSM/GPRS, GPS, and Bluetooth functionalities, making it a powerful solution for IoT (Internet of Things) projects. It is widely used in applications such as vehicle tracking, personal tracking, asset tracking, and remote communication systems. The module allows for sending and receiving SMS messages, making and receiving phone calls, and providing real-time GPS location information.

• Quad-band 850/900/1800/1900MHz GSM/GPRS
• GPS channels: 22 tracking / 66 acquisition
• Bluetooth: 3.0+EDR
• Supply voltage range: 3.4V - 4.4V
• Operating temperature: -40°C to +85°C

• Normal operation: 55mA (average)
• GPRS: max 450mA
• GPS: max 67mA

1. Power Supply: Connect the VCC pin of the SIM808 module to a 3.7V LiPo battery or a regulated 4V power supply. Ensure the ground is connected to the Arduino's GND.
2. Serial Communication: Connect the TXD pin of the SIM808 to the RX pin (Pin 0) of the Arduino and the RXD pin to the TX pin (Pin 1).
3. GPS Antenna: Attach an active GPS antenna to the GPS_ANT pin for accurate positioning.
4. Bluetooth Antenna: Connect a Bluetooth antenna to the BT_ANT pin if Bluetooth functionality is required.

• Always use a stable power supply capable of providing sufficient current during transmission peaks.
• Ensure that the antennas are properly connected and placed for optimal signal reception.
• Use level shifters if necessary, as the logic levels of the SIM808 are 2.8V and may not be directly compatible with some MCUs.

#include <SoftwareSerial.h>

SoftwareSerial sim808(7, 8); // RX, TX

void setup() {
  // Begin serial communication with Arduino and Arduino IDE (Serial Monitor)
  Serial.begin(9600);
  
  // Begin serial communication with SIM808
  sim808.begin(9600);
  
  // Set SIM808 module to SMS mode
  sim808.println("AT+CMGF=1");
  delay(100);
  // Replace with your phone number and message
  sim808.println("AT+CMGS=\"+1234567890\"");
  delay(100);
  sim808.println("Hello from SIM808!");
  delay(100);
  // End AT command with a ^Z, ASCII code 26
  sim808.println((char)26);
  delay(100);
  sim808.println();
  // Give module time to send SMS
  delay(5000); 
}

void loop() {
  // If data is available on SIM808, print it to serial monitor
  if(sim808.available()){
    Serial.write(sim808.read());
  }
  // If data is available on Serial, send it to SIM808
  if(Serial.available()){     
    sim808.write(Serial.read());
  }
}

• Power Issues: If the module does not power on, check the power supply and battery connections.
• Signal Issues: Poor GPS or GSM signal can be due to improper antenna placement or faulty antennas.
• Serial Communication: If there is no response from the module, ensure that the TX and RX pins are correctly connected and the baud rate is set properly.

• Power Supply: Use a high-quality power supply with noise filtering and ensure that the current rating is sufficient for the module's peak requirements.
• Antenna Placement: Place antennas in an open area with a clear view of the sky for GPS and away from metal objects for GSM.
• Level Shifting: Use level shifters between the module and MCU if they operate at different logic levels.

Q: Can I use the SIM808 module for making voice calls? A: Yes, the SIM808 module supports voice calls. You will need to connect a microphone and speaker to the respective pins.

Q: How do I update the firmware of the SIM808 module? A: Firmware updates are provided by the manufacturer and can be uploaded to the module via the serial interface using specific tools and software.

Q: What is the accuracy of the GPS in the SIM808 module? A: The GPS accuracy is typically within 2.5 meters CEP (Circular Error Probable) under open-sky conditions.

Q: Can the SIM808 module be used for data transmission over GPRS? A: Yes, the module can transmit data over GPRS. You will need to set up the proper APN settings and establish a network connection.

Q: How do I send an SMS with the SIM808 module? A: You can send an SMS by issuing the appropriate AT commands over the serial interface, as shown in the sample Arduino code above.