ESP32 Modbus gateway handles RTU, TCP/IP, and MQTT for industrial IoT

Designed by Namnam in Vietnam, the ESP32 Modbus gateway is built to communicate with PLCs and industrial sensors over Modbus RTU (RS-485) or Modbus TCP/IP (Ethernet/Wi-Fi). Designed for use in farms, factories, and electrical cabinets where reliable communication, remote monitoring, and control are required.

Key features of this industrial IoT board include Modbus RTU/TCP master and slave support, automatic Wi-Fi/Ethernet switching, multi-Wi-Fi handling, watchdog timer, deep sleep, and FOTA updates via FTP. The board supports a wide input voltage range and can be programmed over USB.

ESP32 Modbus gateway specifications

• Wireless Module – ESP32-WROOM-32 module with ESP32 dual-core processor @ 160 MHz,  520 Kbytes SRAM, 4 Mbit Flash
• Connectivity
  • 10/100Mbps Ethernet RJ45 port via LAN8720A controller
  • Wifi and WiFi 802.11 b/g/n, Bluetooth 4.2 via ESP32
  • RS485 – SP485EE transceiver (Serial2, auto DERE)
• USB – USB Type-C port for programming and power
• Misc
  • Onboard Red, Blue, and Pwr LED
  • User and Reset buttons
  • Buzzer for notifications
  • Watchdog timer support
  • Deep sleep mode
• Power supply
  • 5V to 35V DC input
  • MC34063A DC-DC converter,
• Dimensions –  Not mentioned

In terms of software support, the ESP32 Modbus RTU/TCP device includes open-source Arduino code examples on GitHub for Modbus RTU/TCP (master and slave), MQTT, FOTA updates, watchdog, deep sleep, and auto Wi-Fi/Ethernet switching.

We have previously written about similar devices like the eModGATE Moduino X0 ESP32-based IoT controller with RS-232, RS-485, and various I/Os, and the MiniLink IIoT Node Arduino-compatible board with an RS-485 interface for sensors or actuators and a DIN rail mount for industrial environments. However, neither supports Ethernet and only relies on WiFi for Modbus RTU/TCP, although the eModGATE Moduino X0 is a complete device with a wider range of wireless options, namely LoRa, Sigfox, and/or LTE-NB/Cat.M1, and an enclosure.

Namnam sells the ESP32-based Modbus gateway on his Tindie store for $35.00 per unit. However, you can get bulk discounts of $29 for 20–49 units, and the price decreases to $25 for 50 units or more.

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