An attempt to recreate the FW for ER G1 glasses. This project uses the NRF DFu as a base to start getting the code to compile because the glasses are known to update with that method.

Based on the size of the binary shipped and the size of the binary generated from the DFU OTA sample code, likely this binary has no custom code in it.

This sample demonstrates how to perform Device Firmware Updates (DFU) simultaneously on both the application core and network core of the nRF5340 DK using Bluetooth Low Energy.

• Prerequisites
• Building the Application
• Deploying to Device
• Performing DFU Over BLE

Before you start, ensure you have:

• nRF5340 DK (Development Kit)
• nRF Connect SDK v2.5.1 or later installed and configured
• Toolchain for nRF Connect SDK v2.5.1 (required compiler and build tools)
• west tool available in your PATH
• nrfjprog command-line tool installed

Important: This sample has been tested with nRF Connect SDK v2.5.1. Using older or newer versions may cause compatibility issues.

The build process compiles the application for the nRF5340 DK with both cores enabled.

west build -b nrf5340dk_nrf5340_cpuapp

What this does:

• Compiles the firmware for both the application core and network core
• Generates the necessary build artifacts including the DFU package
• Places outputs in the build/ directory

After a successful build, you should find:

• build/zephyr/app_signed.hex - Signed application firmware
• build/zephyr/dfu_application.zip - DFU package (used for OTA updates)

This step programs the initial firmware onto the nRF5340 DK and enables the bootloader.

west flash --recover

What this does:

• Erases the entire flash memory on the device (--recover flag)
• Programs the MCUboot bootloader
• Programs the compiled application firmware for both cores
• Prepares the device for DFU updates

Note: This step is only needed once during initial setup. For subsequent firmware updates, use DFU over BLE.

This process updates the firmware on both cores wirelessly using Bluetooth Low Energy.

Download and install the nRF Connect for Mobile app on your smartphone (iOS or Android).

The DFU package was created during the build process at:

build/zephyr/dfu_application.zip

Transfer this file to your mobile phone using:

• USB cable
• Cloud storage (Google Drive, Dropbox, OneDrive)
• Email or messaging apps

For more details about the DFU package format, see the nRF Connect SDK documentation.

1. Open the nRF Connect for Mobile app
2. Tap SCAN to discover nearby Bluetooth devices
3. Find your nRF5340 DK in the list (usually named something like "nrf5340dk" or similar)
4. Tap CONNECT to establish a connection

1. With the device connected, look for the DFU button in the app
2. Tap the DFU button to start the firmware update process

1. When prompted, select the dfu_application.zip file from your phone
2. Choose "Confirm Only" upload mode
3. Tap Start to begin the update

What happens:

• The app transfers the firmware package to the device over BLE
• The bootloader verifies the firmware integrity
• Both the application core and network core are updated simultaneously

After the upload completes successfully, reset the device to apply the update:

nrfjprog --reset

Or simply press the RESET button on the nRF5340 DK.

What this does:

• Restarts the device
• The bootloader processes the new firmware
• Both cores boot with the updated firmware

• Build fails: Ensure your nRF Connect SDK is up-to-date with west update
• Flash fails: Try unplugging and replugging the nRF5340 DK
• DFU fails: Verify the dfu_application.zip file is not corrupted
• Connection drops: Move closer to the device or reduce interference