Why OTA for ESP32 Is Still Too Hard — and What I'm Building to Fix It

ESP32 Updated on August 4, 2025

Introduction

Over-the-air (OTA) firmware updates are essential for modern embedded devices. Whether you're building smart home products, industrial sensors, or wearable devices, the ability to remotely update firmware is critical for long-term reliability, user experience, and security.

The ESP32 is one of the most widely used embedded platforms, but despite its popularity, deploying OTA updates in a secure and maintainable way is still surprisingly difficult.

In this blog series, I’ll be building and documenting an open-source OTA update system for ESP32 devices. This post covers the current landscape, pain points, and the direction of the solution I’m working on.

What's Available Today

Espressif’s official toolchain (ESP-IDF) includes excellent support at the firmware level:

  • OTA partition schemes

  • Multiple firmware slots

  • HTTPS OTA fetching

  • Rollback on failure

These features are solid, but they only solve part of the problem. ESP-IDF gives you the mechanics, but not the infrastructure or workflow. To make OTA work in a real-world project, you still need:

  • A versioning system for firmware

  • A secure firmware hosting and delivery mechanism

  • Cryptographic signing and validation

  • A way to assign versions to specific devices or groups

  • Integration with CI/CD tools like GitHub Actions

  • A user interface to manage and track updates

At the moment, developers are left stitching together these pieces themselves.

Common Workarounds and Their Limitations

1. Custom Python or Node.js Servers

Many developers build simple servers that serve firmware binaries over HTTP or HTTPS. A JSON file often provides the latest version information. This works but is fragile and insecure.

Limitations:

  • No signing or verification of firmware

  • No API for device targeting or version management

  • No built-in CI/CD integration

  • No authentication or deployment tracking

2. Cloud IoT Platforms

Platforms like AWS IoT, ESP RainMaker, and ThingsBoard offer device management and OTA features. These are often used by larger teams or commercial products.

Limitations:

  • Overly complex for small teams or solo developers

  • Requires vendor lock-in

  • Limited control over low-level behavior

  • Difficult to integrate with custom firmware workflows

3. Third-Party Frameworks

Frameworks like Mongoose OS and Tuya include OTA support as part of their ecosystem. While convenient, they are tightly coupled to their own firmware environments.

Limitations:

  • Not suitable if you use ESP-IDF or PlatformIO

  • Often have license restrictions or closed-source components

  • Incompatible with custom bootloaders or partition setups

What’s Still Missing

What the ecosystem lacks is a lightweight, open-source, developer-focused OTA system that works seamlessly with ESP32 and can be integrated into existing workflows.

A better system should include:

  • ESP-IDF and PlatformIO compatibility

  • Secure firmware signing and version management

  • Simple REST API for update checks

  • CI/CD pipeline support for automatic deployments

  • A small OTA agent written in plain C

  • A dashboard or CLI to manage firmware

  • Dockerized and self-hostable infrastructure

In short, we need an OTA system that’s easy to understand, extend, and deploy — without being tied to any cloud provider or complex ecosystem.

What I'm Building

To fill this gap, I’m building an open-source OTA system with the following components:

1. Backend Server
A lightweight Flask or Django application that:

  • Accepts signed firmware uploads

  • Hosts a REST API for devices to check and download the latest firmware

  • Manages firmware metadata and tags

2. OTA Client Agent (C)
A minimal OTA agent that runs on ESP32:

  • Periodically contacts the server for updates

  • Validates the firmware signature before flashing

  • Integrates with ESP-IDF and works with HTTPS

3. CLI Tool and CI/CD Integration
A Python-based CLI tool (ota-cli) that:

  • Signs firmware using ECDSA or RSA

  • Pushes new firmware to the server

  • Can be called from GitHub Actions or other CI workflows

4. Optional Web Dashboard
A simple interface to:

  • Upload firmware

  • Track versions

  • Assign updates to device types or tags

This will all be published under an open-source license, and each component will be documented step-by-step here on the blog.

Who This Is For

This project is built for:

  • Embedded developers who want a clean and secure OTA system

  • Consultants looking to avoid reimplementing the same OTA stack for each client

  • Small product teams who want OTA without AWS or Firebase

  • Educators and students who want to study secure OTA workflows

Whether you're building a single-device prototype or deploying hundreds of units in the field, this system should provide a manageable, extensible starting point.

What's Next

In the next few blog posts, I’ll cover how to:

  • Set up OTA partitions and firmware versions for ESP32

  • Write a minimal OTA agent in C using ESP-IDF

  • Build and host a firmware update server using Flask or Django

  • Add signature-based verification to firmware updates

  • Integrate the OTA system with CI/CD pipelines using GitHub Actions

  • Deploy the backend using Docker, Railway, or Fly.io

The full source code will be published on GitHub, and each component will be explained in depth.

If you’re interested in following the project, subscribe to the blog or follow the GitHub repository once it launches.