How to Use SIM 800A: Examples, Pinouts, and Specs

The SIM 800A is a GSM/GPRS module manufactured by SIMCOM (Part ID: S2-10761-Z1P1K). It is a compact and reliable solution for enabling communication over mobile networks. The module supports SMS, voice calls, and GPRS data transmission, making it a versatile choice for a wide range of applications. Its small form factor and low power consumption make it particularly suitable for IoT devices, remote monitoring systems, and embedded communication solutions.

• Internet of Things (IoT) devices
• Remote monitoring and control systems
• Smart home automation
• Vehicle tracking and fleet management
• SMS-based alert systems
• Wireless data transmission in industrial applications

The SIM 800A module has multiple pins for power, communication, and control. Below is a summary of the key pins:

1. Power Supply: Ensure the module is powered with a stable voltage between 3.4V and 4.4V. A typical 4.0V power source is recommended. Use a capacitor (e.g., 100µF) near the power pins to stabilize the supply.
2. UART Communication: Connect the TXD and RXD pins to the corresponding UART pins of your microcontroller (e.g., Arduino). Use a level shifter if your microcontroller operates at 5V logic levels.
3. SIM Card: Insert a valid SIM card into the SIM card slot. Ensure the SIM card supports GSM/GPRS networks.
4. Power On: Pull the PWRKEY pin low for at least 1 second to power on the module.
5. Network Status: Monitor the NETLIGHT pin to check the network status:
   • Blinking every 1 second: Searching for network
   • Blinking every 3 seconds: Connected to network
6. AT Commands: Use AT commands to configure and control the module. For example:
   • AT: Check communication with the module.
   • AT+CSQ: Check signal quality.
   • AT+CMGF=1: Set SMS mode to text.
   • AT+CMGS="phone_number": Send an SMS.

Below is an example of how to use the SIM 800A with an Arduino UNO to send an SMS:

• SIM 800A TXD → Arduino RX (Pin 0)
• SIM 800A RXD → Arduino TX (Pin 1) (Use a voltage divider if needed)
• SIM 800A GND → Arduino GND
• SIM 800A VCC → 4.0V Power Supply
• SIM 800A PWRKEY → GND (momentarily for power on)

#include <SoftwareSerial.h>

// Define RX and TX pins for SoftwareSerial
SoftwareSerial sim800a(10, 11); // RX = Pin 10, TX = Pin 11

void setup() {
  // Initialize serial communication
  Serial.begin(9600); // For debugging
  sim800a.begin(9600); // For SIM 800A communication

  // Power on the SIM 800A module
  Serial.println("Initializing SIM 800A...");
  delay(1000);

  // Send AT command to check communication
  sim800a.println("AT");
  delay(1000);
  while (sim800a.available()) {
    Serial.write(sim800a.read()); // Print response to Serial Monitor
  }

  // Set SMS mode to text
  sim800a.println("AT+CMGF=1");
  delay(1000);

  // Send an SMS
  sim800a.println("AT+CMGS=\"+1234567890\""); // Replace with recipient's number
  delay(1000);
  sim800a.println("Hello from SIM 800A!"); // SMS content
  delay(1000);
  sim800a.write(26); // Send Ctrl+Z to indicate end of message
  delay(5000);

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

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

• Use a stable power supply to avoid unexpected resets or malfunctions.
• Ensure proper grounding to minimize noise and interference.
• Use a level shifter if your microcontroller operates at 5V logic levels.
• Place the module in an area with good GSM signal strength for reliable operation.

1. Module Not Powering On

   • Ensure the PWRKEY pin is pulled low for at least 1 second.
   • Verify the power supply voltage is within the recommended range (3.4V to 4.4V).

2. No Network Connection

   • Check the SIM card for proper insertion and activation.
   • Verify the antenna is securely connected.
   • Use the AT+CSQ command to check signal strength. A value above 10 is recommended.

3. No Response to AT Commands

   • Ensure the UART connections (TXD and RXD) are correct.
   • Check the baud rate settings (default is 9600 bps).

4. SMS Not Sending

   • Verify the SMS center number is configured correctly using AT+CSCA.
   • Ensure the recipient's phone number is in the correct format.

Q: Can the SIM 800A work with 5V microcontrollers?
A: Yes, but you must use a level shifter or voltage divider for the UART pins to avoid damaging the module.

Q: What is the maximum data rate supported by the SIM 800A?
A: The module supports a maximum GPRS data rate of 85.6 kbps.

Q: How can I reduce power consumption?
A: Use the DTR pin to enable sleep mode when the module is idle. This reduces power consumption to ~1.2mA.

Q: Can the SIM 800A be used for GPS tracking?
A: No, the SIM 800A does not have built-in GPS functionality. However, it can be paired with a GPS module for tracking applications.