We’ll be using the Unbonded version of the Buttonless DFU implementation. We’ll be using the ble_app_blinky example within the nRF5 SDK (v 17.1.0). Our first step is to add the Buttonless DFU service to our application. Adding the Buttonless DFU service and functionality to an nRF52 example Once you have all these requirements satisfied, you can follow along with the steps laid out next. You may also use nrfutil connected via a second nRF52 DK to act as the DFU controller to the target device (refer to the documentation here). nRF Connect for Mobile ( iOS, or Android) or nRF Connect for Desktop if you’re using a PC as the DFU controller.On nRF52840, you can use the CC310 crypto engine which is hardware supported by this DK. If you are using a DK other than the nRF52840, then you may need to install micro-ecc.nrfutil (Python dependent) – needed for generating the cryptography keys and the DFU packages.nRF Command Line Tools (nrfjprog) – download and install to your PC.Segger Embedded Studio – download and install to your PC.nRF5 SDK (version 17.1.0) – download and unzip the SDK to a folder of your choice.(alternatively, you could use a second nRF52 DK along with your development PC and use the Bluetooth Low Energy app within nRF Connect for Desktop) A mobile phone (iOS or Android) – used as the DFU controller.( Note: we’ll be using an nRF52840 DK as our target device).

One nRF52-based development kit – used as the DFU target.

A development PC (Windows, macOS, or Linux) – for building the bootloader and application, and generating cryptographic keys.

There are a few required hardware and software elements for our tutorial: Hardware Requirements In this tutorial, we will be going over the complete steps of how to integrate the Nordic Buttonless DFU into our own application to enable OTA DFU functionality and be able to update the device in the field over Bluetooth Low Energy.

In a few previous posts ( Part 1, Part 2, and Part 3), we covered the basics of designing a secure Over-the-Air Device Firmware Update (OTA DFU) process, an overview of the Nordic nRF52 OTA DFU process, as well as testing out one of the DFU examples included in the nRF5 SDK.

Nrf52 totem pole output