ESPHome can now build firmware for Nordic's nRF52840 Dongle (PCA10059), the small USB stick built around the nRF52840 chip. Pull request #19009, merged into the development branch on 15 October 2026, adds it as board: nrf52840dongle. On 16 October ESPHome Device Builder 1.24.0 followed with a browser flasher that talks to the dongle's factory bootloader.
The factory bootloader stays
Other nRF52 boards in ESPHome use the Adafruit bootloader or MCUboot. The dongle ships with Nordic's own Open DFU bootloader, and ESPHome keeps it: the new bootloader: nrf option reserves the bootloader's flash region, so flashing never overwrites it, and the application is linked at address 0x1000, where that bootloader loads it.
This bootloader accepts only Nordic's Secure DFU protocol. In the author's tests adafruit-nrfutil's legacy serial DFU timed out against it, so ESPHome packages and uploads the firmware with Nordic's nrfutil (nrf5sdk-tools 1.1.0). The first build downloads the launcher into ESPHome's toolchain cache and checks it against the size and SHA-256 that Nordic's file store reports. A user's own ~/.nrfutil is left untouched.
You can enter the bootloader by pressing the dongle's RESET button. With dfu: true in the configuration you do not have to: ESPHome sends the usual 1200 bps "touch" to the running firmware, which then resets itself through pin P0.19, wired to RESET on this board. OTA updates over mcumgr are refused with this bootloader, and uart0 is disabled because its pins are the GPIOs exposed on the dongle's edge.
Flashing from the browser
Device Builder, the ESPHome dashboard, could already flash boards with the Adafruit bootloader from the browser using legacy DFU. Version 1.24.0 adds Secure DFU for Nordic's bootloader, and each nRF52 device is now offered the flasher that matches its own bootloader. MCUboot devices no longer get a DFU option and keep their mcumgr updates. When the dashboard is opened over plain HTTP, where browsers do not offer Web Serial, it can hand the compiled package to web.esphome.io, which gained the same flasher. The author tested these paths on a dongle on 15 October.
There is one catch. According to the Device Builder pull request, the dongle shows up in the dashboard's board list only once Device Builder pins an ESPHome release that includes #19009. ESPHome's development branch is now at 2026.11.0-dev, which points to ESPHome 2026.11.
Device Builder 1.24.0 also brings a fix for encrypted OTA. When Home Assistant hands over a new API key, the dashboard now writes the key the device is still running as ota: encryption: old_key:, so the next install is not refused at the handshake by a device that requires encrypted updates. That part also needs ESPHome 2026.11; with older versions the dashboard logs a warning that the next install needs 2026.11 or a serial flash.