BLE OTA / DFU: Firmware Updates Done Right

Every connected product eventually needs a firmware update. A bug ships, a new feature lands, a security hole is found — and the only way to fix the device sitting in your customer’s pocket is to push new firmware over the air. In the BLE world this is called OTA (Over-The-Air) updating, or DFU (Device Firmware Update).

It sounds simple: send a binary to the device and tell it to reboot. In practice, OTA is one of the most failure-prone flows in any BLE product. A dropped packet, a corrupted image, or a power loss at the wrong moment can turn a $200 device into a brick.

In this article we will build a complete mental model of how BLE firmware updates work, walk through the Nordic DFU approach and a custom protocol, and cover the three things that separate a toy implementation from a production one: integrity verification, resumability, and safe rollback.

Let’s get started!