Project notebook

Modbus Proxy

An embedded bridge built on an ESP32 that exposes data from industrial devices using Modbus over RS-485 as a clean HTTP API and MQTT messages, making legacy energy equipment easy to integrate with modern software systems.

Project brief

What this project is doing

Modbus Proxy is a hardware and firmware project that exposes industrial energy devices such as meters, inverters, batteries, and heat pumps through a modern network API. The system connects to devices using Modbus over RS-485 and translates the data into a structured HTTP interface that can be consumed by software applications.

The project demonstrates the ability to design and deliver a complete system spanning embedded hardware, firmware, API design, and modern software integration.

Problem

Many devices used in energy systems still communicate using Modbus RTU, a protocol designed for serial networks rather than modern software environments. While reliable, this creates several integration challenges:

  • Data is exposed through raw registers rather than structured APIs
  • Access typically requires specialised drivers or polling software
  • Integration with web services, automation platforms, or analytics pipelines is cumbersome
  • Vendor implementations vary, making reuse difficult

These limitations slow down experimentation and product development in energy technology.

Solution

Modbus Proxy provides a lightweight bridge between legacy industrial protocols and modern network software.

The device connects directly to a Modbus network and exposes selected registers through a REST-style API. Software can retrieve data using standard HTTP requests rather than implementing Modbus clients.

The system is built around an ESP32 running firmware developed using ESP-IDF.

Key capabilities include:

  • Polling Modbus RTU devices over RS-485
  • Translating registers into structured data
  • Exposing data via a documented HTTP API
  • Providing a simple integration point for software systems

The result is that industrial devices become accessible like any other network service.

Technical Approach

The project was developed using an AI-assisted iterative workflow inspired by agent-based development patterns. The process involved:

  • Defining a full OpenAPI specification for the device API
  • Generating a product requirements document from the API specification
  • Iteratively implementing firmware using automated development loops
  • Incorporating hardware-in-the-loop validation so the system can test behaviour against the real device

This approach allowed rapid development while maintaining a clear architectural boundary between firmware capabilities and the external API.

Why This Project Matters

Modbus Proxy demonstrates several capabilities relevant to technical leadership or founding roles:

  • Full-stack system thinking spanning hardware, firmware, and application layers
  • API-first design, ensuring clean integration points
  • Rapid prototyping using AI-assisted development workflows
  • Practical experience with industrial energy systems and protocols

The project also sits within a broader exploration of software-defined energy systems, where legacy infrastructure is exposed through programmable interfaces that enable automation, optimisation, and new product ideas.

Strategic Context

Modbus Proxy is part of a wider portfolio of projects exploring energy data, optimisation, and developer-friendly infrastructure for working with energy devices. In particular, it forms the hardware integration layer for projects analysing and optimising household energy usage.

The broader theme is enabling modern software tools to interact with traditionally closed or industrial energy systems, creating opportunities for new products in energy optimisation, monitoring, and automation.

In short, Modbus Proxy demonstrates the ability to identify integration friction in real systems and design pragmatic technical solutions across hardware and software boundaries, a capability that is highly relevant when building new technology companies in complex domains such as energy, infrastructure, or industrial systems.

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