ESP32 IoT Device Simulator

What it is

A simulated supply-chain tracking device on an ESP32, modelling what a real logistics sensor node does end to end: read temperature and humidity from a DHT22, simulate GPS movement around New Delhi with a bounded random walk, track simulated battery drain, and publish it all as JSON to a public MQTT broker every 10 seconds.

Technical notes

• Local status display on an SSD1306 OLED, plus an RGB LED that signals connection state at a glance: yellow while joining WiFi, blue while connecting to MQTT, green once publishing, red on error
• If a sensor read fails, the system reuses the last valid reading rather than dropping the telemetry stream. A real field device doesn’t get to just skip a report
• PubSubClient for MQTT, ArduinoJson for payload serialization, Adafruit SSD1306/GFX for the display stack
• Built and tested in Wokwi’s ESP32 simulator against a public HiveMQ broker

Evidence

The public repository includes the full sketch, the Wokwi circuit diagram, and a simulation screenshot.

Next iteration

The README’s own roadmap is the honest next step: TLS on the MQTT connection, a real dashboard instead of manually watching the broker, and simulating more than one device at once.