SOHO MQTT Multi-Stack Gateway with WIZnet W5500
ESP32 + W5500 gateway links ESP-NOW and LoRa sensor nodes to a Mosquitto broker, delivering a compact yet scalable MQTT system for SOHO environments.
Project Overview
To reduce Wi-Fi AP load and battery constraints, we designed a ESP32 + W5500 multi-stack gateway.
The gateway supports ESP-NOW (short-range), LoRa (long-range) and Ethernet (MQTT) in parallel, abstracting node control/monitoring through a REST-like JSON interface. It integrates with a Mosquitto broker running on a Raspberry Pi 3B and handles real-time data from dozens of nodes.
Key Features
Wired Stability – low-latency, high-reliability MQTT via W5500
Wireless Scalability – up to 20 ESP-NOW slaves; LoRa as long-range fallback
Modular Design – hot-swappable ESP32 cards on a 6-slot backplane
JSON-based SD – payload includes node MAC, type, command, data fields
Lightweight Queueing – 100–300 ms publish spacing to smooth broker bursts
Hardware Setup
Main Board
SPI link: W5500 ↔ ESP32
6 slot connectors (UART, I²C, power)
Slot Card (ESP32)
Vertical header for optional E220-900T22D
On-board antenna for ESP-NOW
Slave Node (ESP8266)
Deep-sleep sensor or relay driver
Li-ion or solar power
Performance Results
| Metric | Average |
|---|---|
| ESP-NOW RTT | 3–5 ms @ -60 dBm |
| LoRa 9600 bps latency | 120 ms / packet |
| MQTT burst (10 msgs) | 40 ms dequeued (100 ms spacing) |
| Gateway CPU load | ≤ 25 % (Wi-Fi off) |
Lessons Learned
SPI Bus – separate CS pins for W5500 and LoRa to avoid contention.
Queue < 100 ms works on Mosquitto + Pi 3B, but LoRa bandwidth becomes the bottleneck.
ChatGPT speeds up code, yet JSON schema still needs human validation.
Future Improvements
Proof-of-concept RabbitMQ/AMQP on an Ubuntu server (9th-gen i7)
Integrate OTA firmware updates
Replace slot cards with ESP32-S3 to add BLE Mesh