SIM800L GPRS GSM Module Core Board Quad-band TTL Serial Port w/ Antenna

Connect the module's TX pin to Arduino pin 2 (SoftwareSerial RX) and RX to pin 3 (SoftwareSerial TX). Supply 3.7V-4.2V to the VCC pin, ensuring peak current of 2A is available. Use a voltage divider on the SIM800L's TX line if your Arduino operates at 5V logic to prevent damage. Initialize communication using SoftwareSerial library at 9600 or 115200 baud for AT commands.

The module includes a solderable wire whip antenna for compact, internal mounting in tight spaces, connecting directly to NET pads. The separate PCB antenna with an IPX connector pigtail offers superior gain and range, and can be mounted externally via its adhesive backing, which is essential if the main module is placed inside a metal enclosure that would otherwise block GSM signals.

After establishing serial communication, send 'AT+CMGF=1' to set SMS text mode. Use 'AT+CMGS="+1234567890"' followed by your message and Ctrl+Z to send an SMS. For voice calls, use 'ATD+1234567890;' to dial and 'ATH' to hang up. Ensure the SIM card is active and the network LED indicates a steady, slow blink for registered signal before issuing commands.

The SIM800L requires a stable 3.7V to 4.2V DC supply capable of delivering a peak current of 2A during transmission bursts, especially when registering on the network or during a call. A high-capacity Li-Po battery or a regulated power supply with low ESR capacitors is recommended. Inadequate current can cause voltage drops leading to module resets or failed network connections.