How to Use SIM900A: Examples, Pinouts, and Specs

The SIM900A is a complete Quad-band GSM/GPRS solution in a compact plug-in module. Manufactured by SivanPeter (Pvt) Ltd., with the part ID 1237602, this module can be integrated into a wide range of electronic projects that require cellular communication such as SMS, data, and voice calls. Common applications include remote data logging, security systems, GPS tracking, and IoT devices.

• Dual-Band 900/ 1800 MHz
• GPRS multi-slot class 10/8
• GPRS mobile station class B
• Compliant to GSM phase 2/2+
  • Class 4 (2 W @ 900 MHz)
  • Class 1 (1 W @ 1800 MHz)

• Standard Commands: GSM 07.07 & 07.05
• Enhanced Commands: SIMCOM AT Commands

• Voltage range: 3.4V - 4.5V
• Recommended voltage: 4.0V

• Dimensions: 24x24x3 mm
• Weight: 3.4g

Note: This is a simplified pin configuration. Refer to the full datasheet for additional pins and detailed descriptions.

To use the SIM900A module with an Arduino UNO, follow these steps:

1. Power Supply: Connect a stable 4.0V power supply to the VCC and GND pins of the SIM900A module.
2. Serial Communication: Connect the RXD pin of the SIM900A to the TX pin of the Arduino, and the TXD pin to the RX pin.
3. Reset: The RST pin can be connected to an Arduino digital pin if software control of the reset function is required.

#include <SoftwareSerial.h>

SoftwareSerial sim900(7, 8); // RX, TX

void setup() {
  // Begin serial communication with Arduino and SIM900A
  sim900.begin(9600);
  Serial.begin(9600);

  // Give time to SIM900A to initialize
  delay(20000);
  Serial.println("Sending Text...");
  sim900.print("AT+CMGF=1\r"); // Set the module to SMS mode
  delay(100);
  sim900.print("AT+CMGS=\"+1234567890\"\r"); // Replace with recipient's number
  delay(100);
  sim900.print("Hello, World!"); // The SMS text you want to send
  delay(100);
  sim900.write(26); // ASCII code of CTRL+Z to send the SMS
}

void loop() {
  // If data is available on the SIM900A, print it to the serial monitor
  if(sim900.available()) {
    Serial.write(sim900.read());
  }
  // If data is available on the serial monitor, send it to the SIM900A
  if(Serial.available()) {
    sim900.write(Serial.read());
  }
}

Note: Make sure to replace "+1234567890" with the actual recipient's phone number.

• Ensure the power supply can deliver enough current for the peak consumption of the SIM900A module.
• Use level shifters if necessary, as the logic levels of the SIM900A are 2.8V and may not be directly compatible with some microcontrollers.
• Antenna connection is crucial for signal strength and quality. Use an appropriate GSM antenna and ensure it is securely connected to the module.

• Power Issues: If the module does not power up, check the power supply and connections.
• Signal Strength: Poor signal strength can lead to communication failure. Ensure the antenna is properly connected and positioned.
• Serial Communication: If there is no response from the module, verify the baud rate and wiring.

Q: Can the SIM900A module be used for internet connectivity? A: Yes, the SIM900A supports GPRS for internet connectivity, but it is limited to 2G networks.

Q: How do I know if the SIM900A module is connected to the network? A: The AT+CREG? command can be used to check the network registration status.

Q: What is the default baud rate of the SIM900A module? A: The default baud rate is 9600 bps.

For further assistance, please refer to the manufacturer's datasheet and technical support resources.