How to Use SIM800c GSM Module: Examples, Pinouts, and Specs

The SIM800c GSM Module is a versatile and compact electronic component that provides GSM/GPRS communication capabilities to embedded systems. It enables devices to make phone calls, send and receive SMS messages, and connect to the internet through GPRS. This module is widely used in various applications such as remote data logging, security systems, automotive and mobile applications.

• Remote monitoring and control systems
• Vehicle tracking with GPS data transmission
• SMS-based remote alerts and automation
• IoT devices requiring cellular network connectivity
• Emergency call systems

• Frequency Bands: Quad-band 850/900/1800/1900MHz
• GPRS Data: Downlink/uplink transfer: max 85.6 kbps
• Transmission Power:
  • Class 4 (2W) for GSM850 and EGSM900
  • Class 1 (1W) for GSM1800 and GSM1900
• Power Supply: 3.4V - 4.4V (Typical 4.0V)
• Operating Temperature: -40°C to +85°C

1. Power Supply: Connect a stable power source to the VCC and GND pins. Ensure that the voltage is within the specified range.
2. Serial Communication: Connect the RXD and TXD pins to the corresponding TX and RX pins of your microcontroller or UART interface.
3. SIM Card: Insert a SIM card into the SIM card holder of the SIM800c module.
4. Antenna: Attach a GSM antenna to the module to ensure proper signal reception and transmission.
5. Audio (Optional): If voice functionality is required, connect a microphone and speaker to the MIC+/- and SPK+/- pins, respectively.

• Always use a regulated power supply to prevent damage to the module.
• Ensure that the antenna is properly connected before powering up the module.
• Use level shifters if the microcontroller operates at a different logic level than the module.
• Follow ESD precautions when handling the module to avoid static damage.

#include <SoftwareSerial.h>

SoftwareSerial sim800c(7, 8); // RX, TX

void setup() {
  // Begin serial communication with Arduino and Arduino IDE (Serial Monitor)
  Serial.begin(9600);
  
  // Begin serial communication with SIM800c and set baud rate
  sim800c.begin(9600);
  
  // Set module to SMS mode
  sim800c.println("AT+CMGF=1\r");
  delay(1000);
  
  // Set module to receive SMS in text mode
  sim800c.println("AT+CNMI=1,2,0,0,0\r");
  delay(1000);
}

void loop() {
  // Check if the SIM800c module is sending a message
  if (sim800c.available()) {
    Serial.write(sim800c.read());
  }
  
  // Check if the Serial Monitor is sending a message
  if (Serial.available()) {
    sim800c.write(Serial.read());
  }
}

• Power Issues: If the module does not power up, check the power supply and connections.
• Signal Issues: Poor signal quality can affect communication. Ensure the antenna is properly connected and positioned.
• SIM Card Issues: If the module cannot connect to the network, verify that the SIM card is active and properly inserted.

• Power Supply: Use a multimeter to verify the voltage at the VCC pin.
• Signal Strength: Use the AT command AT+CSQ to check the signal quality.
• SIM Card: Ensure the SIM card has no PIN code or use the AT command AT+CPIN to enter the PIN.

Q: Can the SIM800c module connect to a 5V logic microcontroller directly? A: No, a level shifter is recommended to convert the 5V logic level to the 3.3V level required by the SIM800c module.

Q: How can I send an SMS using the SIM800c module? A: Use the AT command AT+CMGS="phone_number" followed by the message and a Ctrl+Z character to send an SMS.

Q: What is the baud rate for communication with the SIM800c module? A: The default baud rate is 9600 bps, but it can be configured with the AT command AT+IPR.

Q: How do I reset the SIM800c module? A: The module can be reset by pulling the RST pin low for a short period.