The HW-537 is a mini development board based on the SIM800C GSM/GPRS module. It supports quad-band GSM, Bluetooth 3.0, and serial communication via UART, making it ideal for embedded wireless applications such as SMS control, IoT telemetry, and remote monitoring.

Specifications

• GSM Module: SIMCom SIM800C
• Frequency Bands: Quad-band 850/900/1800/1900 MHz
• Bluetooth: v3.0 (SPP profile, AT command controlled)
• Operating Voltage:
  - 5 V via onboard regulator
  - 3.4–4.4 V via VBAT (direct battery input)
• Logic Level: 3.3 V / 5 V TTL compatible (selectable via V_TTL pin)
• Communication Interface: UART (TXD, RXD)
• Baud Rate: 1200–115200 bps (default 9600)
• Antenna Interface: IPEX connector (supports PCB or IPEX-SMA antenna)
• SIM Slot: Micro SIM card slot
• Power Supply: Requires ≥ 2 A peak current for GSM transmission
• Onboard Components:
  - AMS1117 5 V regulator
  - TX/RX level shifter
  - Status LEDs
• Dimensions: ~40 mm × 30 mm
• Mounting: 4 × M3 holes

Features

• Supports SMS, voice calls, GPRS data, and Bluetooth serial communication
• Compatible with Arduino, STM32, ESP32, and other UART-based MCUs
• AT command set: 3GPP TS 27.007, 27.005 + SIMCom extensions
• Ideal for remote control, telemetry, and GSM-based IoT projects
• Common use cases:
  - SMS-based automation and alerts
  - Bluetooth-to-GSM bridges
  - GPS tracker communication modules
  - IoT telemetry and data logging over GPRS