Product Overview
The ESP-M2 WiFi Serial Transparent Transmission Module is a compact, high-performance wireless communication solution designed to bridge the gap between serial devices and Wi-Fi networks. Built around the powerful ESP8285 chip—an enhanced version of the legendary ESP8266 with integrated flash memory—this module provides a seamless “plug-and-play” solution for adding wireless connectivity to your existing projects .
What sets the ESP-M2 apart is its preloaded transparent transmission firmware. This means the module comes ready to use right out of the box: simply connect it to your device’s UART (serial) port, and it will automatically forward any data received over the serial interface to a Wi-Fi network (and vice versa) . There is no need for complex programming or custom firmware development—the module handles all the network protocol details automatically .
Whether you need to retrofit legacy industrial equipment with wireless monitoring, build a wireless data logger, or create a remote control system for a robot or smart home device, the ESP-M2 provides a reliable, cost-effective solution. Its integrated PCB antenna delivers solid wireless performance, while its ultra-low power consumption (down to 20µA in deep sleep) makes it suitable for battery-powered applications .
Key Features
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Plug-and-Play Serial-to-WiFi Bridge: Preloaded with industrial-grade transparent transmission firmware (V3.0) that automatically forwards data between your serial device and a Wi-Fi network—no programming required .
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Integrated 32-bit Processor: Built around the ESP8285 chip (ESP8266 with integrated 1MB flash), featuring a Tensilica L106 32-bit RISC processor running at up to 160 MHz .
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Complete Wi-Fi Solution: Supports 802.11 b/g/n protocols at 2.4 GHz with integrated PCB antenna. Delivers up to 15dBm output power with excellent receiver sensitivity down to -96dBm .
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Rich Interface Options: Provides UART, SPI, I2C, I2S, PWM, and 10-bit ADC interfaces, allowing connection to a wide variety of sensors and actuators .
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Built-in Web Configuration Server: Features an onboard HTTP web server that allows you to configure all module parameters (Wi-Fi credentials, network mode, serial settings, etc.) through a simple web browser—no additional software or apps required .
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Multiple Operating Modes: Supports Station (STA), Access Point (AP), and Station+AP modes, enabling devices to connect to existing networks or create their own .
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Ultra-Low Power Consumption: Features multiple sleep modes with deep sleep current as low as 20 µA and standby power consumption less than 1.0 mW. Wake up and transmit packets in less than 2 ms .
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Wide Operating Voltage: Accepts supply voltage from 4.5V to 6.0V (recommended 5V), with TTL logic levels compatible with both 3.3V and 5V systems .
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Industrial Temperature Range: Rated for operation from -40°C to +125°C, making it suitable for demanding industrial environments and outdoor installations .
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OTA Firmware Updates: Supports Over-The-Air (OTA) firmware updates, allowing you to upgrade the module’s firmware wirelessly .
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State Indicator Output: Provides a dedicated STATE pin (GPIO4) that outputs a low signal when the module is successfully connected to a Wi-Fi network, simplifying status monitoring .
Technical Specifications
Pinout & Interface Guide
The ESP-M2 module is typically mounted on a convenient carrier board (DT-06 or similar) that provides easy access to all essential pins.
Boot Mode Configuration
The module’s boot mode is determined by the state of GPIO0 and GPIO15 :
Note: GPIO15 is already pulled LOW internally on the module. To enter programming mode, you need to pull GPIO0 LOW during boot (using the onboard button or external connection).
Status LED Indicator
The onboard STATE LED provides visual feedback of the module’s Wi-Fi connection status :
Usage Guide
Getting Started
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Power the Module: Connect a 5V DC power supply to the VCC and GND pins. The onboard LED should illuminate.
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Connect to Your Serial Device: Connect the module’s TXD pin to the RX pin of your device, and RXD to the TX pin. If your device uses 5V logic, the module’s 3.3V TTL pins are 5V tolerant due to built-in series resistors .
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Connect to the Module’s Configuration Network: By default, the module boots in AP (Access Point) mode. Use your computer or smartphone to scan for Wi-Fi networks and connect to the SSID: “Minibalance_XXXXXX” (where XXXXXX is the last six digits of the module’s MAC address). The default password is 12345678 .
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Open the Web Configuration Page: Open a web browser and navigate to 192.168.4.1. You will see the module’s configuration interface .
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Configure Your Settings: Use the web interface to:
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Set the module to STA (Station) mode and enter your home Wi-Fi credentials
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Configure the serial port settings (baud rate, data bits, parity, stop bits)
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Set the network protocol (TCP Server, TCP Client, UDP, etc.)
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Save the configuration
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Start Transparent Transmission: Once configured, the module will automatically connect to your Wi-Fi network and begin forwarding data between the serial port and the network.
Web Configuration Overview
The module’s built-in web server provides several configuration pages :
Connection Diagrams
Basic Connection to a Microcontroller:
ESP-M2 Module Microcontroller (Arduino/STM32/etc.)
TXD -----> RXD
RXD <----- TXD
GND -----> GND
VCC -----> 5V (external supply)
Baud Rate Compatibility:
The module supports a wide range of baud rates, making it compatible with virtually any serial device :
AT Command Examples
The module also supports standard AT commands for configuration and control :
AT // Check communication
AT+GMR // Check firmware version
AT+CWMODE=1 // Set to Station mode
AT+CWJAP="SSID","PASSWORD" // Connect to Wi-Fi
AT+CIPSTART="TCP","192.168.1.100",8080 // Open TCP connection
AT+CIPSEND=5 // Send data
> HELLO // Data to send
Q: What is the difference between ESP-M2 and other ESP8266 modules?
The ESP-M2 uses the ESP8285 chip , which is essentially an ESP8266 with 1MB of integrated flash memory . This eliminates the need for an external flash chip, resulting in a more compact design. The module comes preloaded with transparent transmission firmware, making it ready to use as a serial-to-WiFi bridge out of the box
Q: Do I need to write any code to use this module?
No. The module is preloaded with industrial-grade transparent transmission firmware (V3.0). You only need to configure it via the web interface (or AT commands) to set your Wi-Fi credentials and serial parameters. After that, it automatically forwards data between your serial device and the network
Q: What types of devices can I connect to the ESP-M2?
The module connects via standard UART (serial) interface. It can interface with:
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Microcontrollers (Arduino, STM32, ESP32, etc.)
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Industrial PLCs and controllers
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Sensors and data acquisition systems
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Any device with a TTL serial port
Q: Can I use the ESP-M2 with 5V logic devices?
Yes. The module’s TXD and RXD pins have built-in 22Ω series resistors and are 5V tolerant, allowing direct connection to 5V logic devices without level shifters
Q: What is the maximum range of the ESP-M2's Wi-Fi connection?
With its PCB antenna, the ESP-M2 achieves ranges of up to 100-200 meters in open space. In practical indoor applications with walls and obstacles, the range is typically 30-50 meters.
Q: What voltage does the ESP-M2 require?
The module requires a supply voltage of 4.5V to 6.0V DC, with 5V recommended. Do not apply 3.3V directly to the VCC pin—the module has an onboard regulator that requires at least 4.5V to function properly
Q: How much current does the ESP-M2 draw?
Current consumption varies by operating mode :
Q: Can I power the ESP-M2 with batteries?
Yes. The module’s deep sleep current of 20µA makes it suitable for battery-powered applications. A 5V boost converter or a 4.5-6V battery pack is required.
Q: How do I connect the module to my device?
Connect the module’s TXD to your device’s RX, RXD to your device’s TX, and GND to GND. Power the module with a separate 5V supply. No additional resistors or level shifters are needed for 5V logic devices
Q: How do I access the web configuration page?
By default, the module boots in AP mode with SSID “Minibalance_XXXXXX”. Connect to this network (password: 12345678), then open a web browser and navigate to 192.168.4.1
Q: What if I forget my Wi-Fi credentials or lock myself out?
You can reset the module to factory defaults by holding the GPIO0 button while powering on or pressing the reset button. This will restore the default AP mode configuration
Q: The module is not connecting to my Wi-Fi network. What should I check?
Verify the following:
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Your Wi-Fi network operates on 2.4 GHz (5 GHz is not supported)
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The SSID and password are entered correctly in the web configuration (case-sensitive)
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Your router is not blocking new devices
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Check the STATUS LED—if it’s blinking slowly, the module is not connected
Q: Can I use AT commands instead of the web interface?
Yes. The module supports standard ESP8266 AT commands over the serial interface at 115200 baud (default). AT commands end with a new-line (CR-LF)
Q: What is the STATUS LED telling me?
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Solid ON: Connected to Wi-Fi network
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Slow blink (1 sec): Not connected, or in AP mode waiting for connections
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Fast blink: Data transmission in progress
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OFF: No power or firmware issue
Q: What can I build with the ESP-M2?
Popular applications include :
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Wireless data acquisition: Replace cables with wireless links for sensors and instruments
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Industrial equipment retrofitting: Add Wi-Fi monitoring to legacy machinery
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Smart home devices: Wireless control of lights, appliances, and HVAC
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Robot control: Remote control via Wi-Fi for robotic platforms
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Wireless serial printers: Eliminate cables for point-of-sale or industrial printers
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Remote sensor networks: Deploy battery-powered sensors with data logging
Q: Is the ESP-M2 suitable for industrial applications?
Yes. The module is rated for operation from -40°C to +125°C, making it suitable for demanding industrial environments and outdoor installations
Q: Can I update the firmware over-the-air?
Yes. The module supports OTA (Over-The-Air) firmware updates, allowing you to upgrade the firmware wirelessly without physical access
Q: Is the ESP-M2 compatible with the ESP8266 Arduino environment?
Yes. Since the ESP8285 is fully compatible with ESP8266, you can re-program the module using the Arduino IDE if you wish to develop custom firmware. The module’s GPIO pins are accessible for custom I/O
