Modbus Gateway UNO-MBGW-P4
An industrial-grade ESP32-P4 gateway that bridges Modbus RTU/TCP field devices to ThingsBoard over MQTT. Isolated RS485, store-and-forward buffering, and a modern web UI — built for the factory floor and DIN-rail cabinets.
What it does
Factories are full of Modbus devices — meters, drives, PLCs, sensors — speaking RS485 (RTU) or Modbus TCP. The Modbus Gateway polls them all, decodes the raw registers into meaningful tags, and forwards the data to ThingsBoard over MQTT (TLS). Configuration follows a subset of the ThingsBoard IoT Gateway JSON format, so existing setups map across cleanly.
Designed for 10–30 devices, ~500 tags, at 500 ms–2 s polling — a commercial product aimed at real industrial deployments.
How it's built
Three isolated RS485 RTU buses plus a Modbus TCP pool feed a polling engine; values are aggregated and buffered in PSRAM (store-and-forward, so nothing is lost when the network drops), then published to ThingsBoard. A built-in web server exposes a live UI over HTTP + SSE.
Modbus devices ──► RS485-1/2/3 (RTU) + Modbus TCP
│
ESP32-P4 Gateway
├─ Modbus engine (3 buses + TCP pool)
├─ Aggregator + buffer (PSRAM, store-and-forward)
├─ ThingsBoard MQTT client (TLS)
└─ Web UI (HTTP + SSE)
│ Ethernet
ThingsBoard
Key features
3× isolated RS485
Three independent RTU buses via isolated transceivers (ADM2483), plus Modbus TCP — poll many devices at once.
ThingsBoard native
Gateway-mode MQTT telemetry with a config schema that's a subset of the ThingsBoard IoT Gateway Modbus connector.
Store-and-forward
Telemetry is buffered in PSRAM (and a flash journal) so data survives network or broker outages and back-fills on reconnect.
Modern web UI
A Vue 3 + TypeScript interface served from on-device flash: dashboard, config editor, live monitor, bus sniffer, settings and OTA.
Live monitoring
Real-time tag values and a Modbus frame sniffer stream to the browser over Server-Sent Events — no polling the UI.
Rugged by design
Wide-input 9–36 V DC or PoE (802.3at), DIN-rail enclosure, Ethernet-primary with optional Wi-Fi.
A/B OTA
Dual-partition over-the-air updates for safe field upgrades of the gateway firmware.
Certification-bound
Engineered toward CE, FCC and NBTC (Thailand) for commercial deployment.
Hardware
- MCU: ESP32-P4 (16 MB flash, 32 MB PSRAM)
- Ethernet: IP101GRI PHY (PHY-sourced RMII clock to avoid the P4 PSRAM/MPLL conflict)
- Serial: 3× isolated RS485 transceivers (ADM2483)
- Wi-Fi (optional): ESP32-C6 co-processor over SDIO (ESP-Hosted); Ethernet stays primary
- Power: wide-input 9–36 V DC or PoE (IEEE 802.3at)
- Enclosure: DIN-rail, built for industrial cabinets
A product of UnoIOT / Synergy Technology Co., Ltd. (SYNTECH). Reference platform: ESP32-P4-Function-EV-Board; production hardware in design.