The SIM800C GSM/GPRS Module is a versatile cellular development breakout board engineered for remote telemetry, IoT sensing, voice communication, SMS notifications, and wireless data streaming. Built around the SIMCom SIM800C quad-band engine, it features Bluetooth 3.0 SPP, DTMF decoding, Text-to-Speech (TTS), and flexible power inputs (accepting wide DC voltage or direct single-cell LiPo batteries). Standard 3.3V/5V TTL serial communication via AT commands allows straightforward interfacing with microcontrollers, Arduino boards, and PC serial adapters.

Specifications

• Core Cellular Chipset: SIMCom SIM800C Quad-Band Engine (850 / 900 / 1800 / 1900 MHz)
• Wireless Protocol: 2G GSM / GPRS (Supports standard 2G/3G/4G SIM cards on 2G-compatible networks)
• Bluetooth Protocol: Bluetooth 3.0 with SPP (Serial Port Profile) and audio services
• Operating Supply Voltage:
  • VCC_IN: 5V to 18V DC (Onboard step-down regulator, accepts up to 20V max)
  • BAT: 3.3V to 4.4V DC (Direct input for 3.7V LiPo or 18650 lithium cells)
• Peak Transmission Current: Up to 2A (Burst current during RF transmissions)
• Serial Logic Level: 3.3V / 5V TTL (Auto-matched via V_M pin)
• Command Interface: Standard and enhanced AT command sets
• Advanced Features: TTS (Text-to-Speech), DTMF detection, SMS, Voice calls, GPRS TCP/IP stack
• SIM Card Slot: Push-pull / self-ejecting Micro-SIM slot
• RF Connectors: Onboard SMA female connector, IPEX (U.FL) pad, and helical spring antenna footprint

Pinout and Interface Guide

• VCC_IN: Main DC Power Input (5V to 18V DC, requires at least 2A peak capability).
• GND: Common System Ground Reference.
• BAT: Direct lithium battery power input (3.3V to 4.4V DC).
• TXD: Primary TTL Serial Output (Transmits AT responses to MCU RX).
• RXD: Primary TTL Serial Input (Receives AT commands from MCU TX).
• V_M: Microcontroller logic voltage reference pin (Connect to MCU 3.3V or 5V rail for precise level matching; can be left unconnected if using default onboard matching).
• PWR: Module power enable control pin (Pull LOW to toggle module power state).
• RI: Ring Indicator output (Pulses LOW on incoming call or SMS).
• DTR: Data Terminal Ready sleep wake-up pin.
• U2_T / U2_R: Secondary auxiliary serial UART pins (Transmit / Receive).
• ADC: Onboard analog-to-digital converter input pin.
• SPP / SPN: Differential audio speaker outputs (Positive / Negative).
• MC+ / MC-: Differential electret microphone audio inputs (Positive / Negative).

Key Features

• Dual Power Flexibility: Can be powered via wide DC voltage (5V–18V) through onboard buck conversion, or directly from a single-cell 3.7V LiPo/18650 battery via the BAT terminal.
• Built-in Bluetooth 3.0: Enables local wireless SPP serial telemetry and audio streaming alongside long-distance cellular links.
• Onboard Level Shifter: Dedicated V_M matching pin ensures clean, level-safe communication with both 3.3V (ESP32, STM32, Raspberry Pi) and 5V (Arduino Uno, PIC) logic without external level converters.
• Versatile Antenna Support: Features an SMA screw connector for the included stub antenna, plus solder footprints for IPEX micro-coaxial connectors and compact helical spring antennas.
• Integrated Audio Processing: Dedicated differential microphone and speaker breakout pins support voice calls and DTMF remote-control decoding.

Common Applications

• Remote IoT Telemetry: Logging environmental or agricultural data to remote cloud servers via GPRS TCP/UDP/HTTP.
• SMS Alert & Alarm Systems: Triggering instant security alerts, power outage notifications, or perimeter alarms to mobile phones.
• Remote Equipment Control: Switching relays and machinery via incoming SMS commands or DTMF keypad tones during a live phone call.
• Vehicle & Asset Monitoring: Telematics tracking when paired with a standalone GPS module.

Operating and Network Status Guide

• Connecting to PC / MCU: Connect module TXD to MCU/USB-TTL RX, and module RXD to MCU/USB-TTL TX. Ensure common GND is shared between the module and controller.
• LED Status Indicators:
  • Flashing 1 time per second: Searching for network, SIM card missing, or registering to the cellular network.
  • Flashing 1 time every 3 seconds: Successfully registered to the GSM network; idle and ready for AT commands, calls, and SMS.
  • Rapid flashing (continuous): Active GPRS data transmission in progress.

Usage Tips

• Power Supply Headroom: Cellular modules draw brief current spikes up to 2A during RF bursts. Powering directly from a standard computer USB port or a weak 500mA regulator will cause brownouts and continuous reboots. Always use a dedicated 5V/2A or 12V/1A power supply.
• SIM Card Selection: Use a standard registered SIM card with an active voice/SMS plan. Ensure the network provider maintains active 2G (GSM) band coverage in your region.
• Antenna Requirement: Never transmit or power up the module without an antenna connected to the SMA port, as RF reflection can degrade the transmitter amplifier over time.