Device Firmware Update (DFU)

Lifecycle: In production

There are two different options on how to update RuuviTag firmware.

OTA (Over the Air)

Ruuvi firmware version 1.x, 2.x

Ruuvitag firmware version up until 2.x are built on top of Nordic SDK 12.3 / Softdevice s132 v3.1.1. The bootloader on these RuuviTags uses debug-mode which skips hardware and firmware version checks.

The keyfile to sign the RuuviTag updates is published in ruuvitag_fw repository.

Command to generate DFU package for RuuviTags up to firmware version 2

nrfutil pkg generate --debug-mode --application _build/ruuvi_firmware.hex --hw-version 3 --sd-req 0x91 --key-file ~/git/ruuvitag_fw/keys/ruuvi_open_private.pem

To upload package to RuuviTag, press button "B" and tap "R" to reset the tag. Bootloader checks if button "B" is pressed at boot and enters the bootloader mode.

Ruuvi firmware version 3.x

Ruuvi firmware 3 builds on SDK15.3 and Softdevice s132 v6.1.1. There are special edition RuuviTags with nRF52811 that do not have bootloader at all due to size constraints.

The bootloader is a production version and it enforces version checks. On RuuviTag B1 ... B7.1 the hardware version is 0xB0, regardless of which sensors are installed.

Command to generate DFU package for RuuviTags with firmware version 3

nrfutil pkg generate --application _build/nrf52832_xxaa.hex --application-version 1 --hw-version 0xB0 --sd-req 0xB7 --key-file ruuvi_open_private.pem ${BINNAME}

In bootloader mode the tag advertises itself with name "RuuviBoot" and it provides BLE DFU Service. Nordic Semiconductor provides libraries for iOS and Android to interface with the service.

SWD (Serial Wire Debug)

If you're developing your own firmware or need to flash hunderds or more of RuuviTags, you should consider using a wired programmer for higher programming speed. To create your own hex image for flashing, you need 4 parts:

  • Softdevice

  • Bootloader

  • Bootloader settings

  • Application

The softdevice is given by Nordic Semiconductor or other company which provides the radio protocol.

You can use Ruuvi's bootloader available at, but you should at least change the public key used for verifying the firmware images to ensure that you can keep the full control of your tags.

Settings are generated with nrfutil, which is part of Nordic Command Line Tools. You'll also need nrfjprog and mergehex from the command line tool package.

Application is the .hex file you have created.

Commands to generate application settings and merge them into one package

nrfutil settings generate --family NRF52 --application _build/nrf52832_xxaa.hex --application-version 1 --bootloader-version 1 --bl-settings-version 1 settings.hex

mergehex -m ../../../../nRF5_SDK_15.3.0_59ac345/components/softdevice/s132/hex/s132_nrf52_6.1.1_softdevice.hex $BOOTLOADER settings.hex -o sbc.hex

mergehex -m sbc.hex _build/nrf52832_xxaa.hex -o packet.hex

Commands to flash the package to RuuviTag

nrfjprog --eraseall

nrfjprog --program packet.hex

nrfjprog --reset

If your firmware is secret or you wish to avoid duplications by users, you should enable the read protection bit .

nrfjprog -f nrf52 --rbp ALL

If you have enabled the read protection, you must run nrfjprog --recover to use the programming interface again. This completely erases the tag.

Always power cycle the tag after using a wired programmer. Otherwise the debug interface might remain active and consume excess current.

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