SIM900A GSM/GPRS Wireless Data Transmission Module Dual-Band SMS Voice MMS Development Board Compatible with 3.3V/5V MCU

SIM900A Module Product Overview

The SIM900A module is a wireless communication module based on SIMCom's industrial-grade dual-band GSM/GPRS chip. Operating on the 900/1800MHz dual-band, SIM900A module enables voice calls, SMS (including MMS), GPRS data transmission, and fax with low power consumption. The module uses a stamp-hole package with a compact size (24×24×3mm), making SIM900A module ideal for integration into various embedded products. SIM900A module features a built-in TCP/IP protocol stack and can be controlled via simple AT commands, lowering the development barrier. Compared to the traditional TC35i module, SIM900A module offers lower power consumption, a smaller footprint, and enhanced functionality, making it a perfect choice for industrial remote monitoring, smart metering, vehicle positioning, and agricultural sensor data backhaul.

SIM900A Module Key Features

Industrial-Grade Dual-Band GSM/GPRS Engine: Powered by a SIMCom industrial-grade chip, SIM900A module operates on EGSM 900MHz and DCS 1800MHz bands. SIM900A module features low power consumption with standby current below 18mA and sleep mode current as low as 1.5mA to 2mA. SIM900A module is compliant with GSM phase 2/2+ standards, supporting GPRS multi-slot Class 10/8.

Rich Interfaces & Wide Voltage Support: SIM900A module provides RS232 and LVTTL serial interfaces with hardware flow control. The TTL level is auto-adaptable for 3.3V and 5V microcontrollers, allowing direct connection to 5V (e.g., 51 series) and 3.3V (e.g., STM32) MCUs. SIM900A module supports a wide power supply range from 5V to 24V. A 1000μF capacitor is added to the 5V input, enabling initial debugging via computer USB power. For extended data transmission, a 1A or higher DC power supply is recommended.

Comprehensive Wireless Communication: SIM900A module supports SMS (TEXT and PDU modes), voice calls (external audio circuit required), MMS, and GPRS data transmission. SIM900A module integrates a TCP/UDP protocol stack for rapid network connection setup via AT commands. SIM900A module also features DTMF for remote control applications.

Development-Friendly Hardware: Onboard RS232 level shifting and TTL interfaces, with accessible reset pins and an SMA antenna interface. SIM900A module's serial circuit is protected by TVS and beads, and the SIM card circuit includes an SMF05C ESD protection chip, enhancing module reliability.

SIM900A Module Applications

The SIM900A module is widely used in fields requiring stable, low-cost, long-range wireless communication:

Industrial Automation & Control: PLCs, industrial instruments, remote data acquisition, equipment monitoring.

Smart Home & Security: Remote alarm systems, access control, smart appliances.

IoT & Agricultural IoT: Smart meters (electricity, water, gas), agricultural greenhouse environmental monitoring.

Vehicle & Positioning: Vehicle anti-theft, GPS trackers, fleet management.

Emergency & Alert Systems: Fire alarms, gas leak detection, remote voice alerts.

Education & Development: University robotics competitions, graduation projects, embedded wireless communication teaching.

SIM900A Module Advantages

Exceptional Cost-Effectiveness: As a classic GSM/GPRS module, SIM900A module offers stable and reliable communication at a highly competitive price, ideal for cost-sensitive projects.

Strong Compatibility, Low Barrier to Entry: Auto-adaptable 3.3V/5V TTL levels allow direct connection to various mainstream MCUs. All functions of SIM900A module are controlled via standard AT commands, eliminating complex protocol development.

Excellent Power Management: SIM900A module sleep mode current is as low as 1.5mA, making it ideal for battery-powered remote monitoring and data acquisition applications.

Robust Protection for Reliability: Onboard TVS, beads, and ESD chips effectively guard against surges, static electricity, and voltage spikes, ensuring stable operation of SIM900A module in complex environments.

All-in-One Functionality: SIM900A module integrates SMS, voice, MMS, and GPRS data transmission with a built-in TCP/IP stack, meeting most wireless communication needs.

Mature Ecosystem, Abundant Resources: As a market-proven classic module, SIM900A module is supported by a wealth of learning materials, open-source projects, and mature commercial applications, enabling developers and engineers to get started quickly.

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FAQs:

1  What is the SIM900A module
SIM900A module is a high-performance dual-band GSM/GPRS wireless communication module from SIMCom, widely used for SMS, voice calls, and GPRS data transmission in embedded systems.

2 What are the core functions of this module
SIM900A module supports voice, SMS including Chinese, and GPRS Class 10 data internet access on 900/1800MHz bands. SIM900A module features a built-in TCP/IP protocol stack and is controlled via AT commands.

3 What are the power supply requirements
While the chip's rated voltage is 3.4V-4.8V, the development board for SIM900A module typically requires 5V. The transient current can reach 2A, so a 1A+ DC power supply or power bank is highly recommended for SIM900A module.

4 What communication interfaces does it support
SIM900A module features standard TTL serial ports compatible with 3.3V and 5V MCUs, and includes an onboard RS232 level converter, allowing direct connection to PCs via USB-to-RS232 cables for debugging.

5 What type of SIM card does it support
SIM900A module supports China Mobile and China Unicom 2G/3G/4G downgraded SIM cards. SIM900A module does not support China Telecom SIM cards, and some cards may require real-name activation.

6 How to connect to STM32 or 51 microcontrollers
 Connect the MCU's TX to the module's RX and the MCU's RX to the module's TX, ensuring common ground. In TTL mode, connect VCC_MCU to 3.3V for 3.3V systems and to 5V for 5V systems when using SIM900A module.

7 How to develop software and test commands
Control SIM900A module using the standard AT command set via serial. Key commands include: AT (test), AT+CPIN? (SIM status), AT+CMGF=1 (text mode), and AT+CMGS="number" (send SMS).

8 What status indicators are available
SIM900A module usually has power and network LEDs. After power-on, checking the blink patterns of LED D5 and D6 can roughly tell you whether SIM900A module has successfully searched for and registered on the network.

9 What are the advantages over the discontinued TC35i
SIM900A module has significant advantages: SIM900A module includes a built-in TCP/IP stack, lower power consumption, and a smaller SMT package for easier soldering, offering better cost-effectiveness.

10 What are the important usage precautions
An external antenna must be attached to SIM900A module. While USB power may work initially for simple tests, operations like sending SMS or data calls cause high peak currents that can reset SIM900A module. Always ensure a robust power supply for SIM900A module.