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Legacy device. DevKit 2 is no longer the current development hardware. The consumer Omi (CV1) is. This page is kept for builders who already own a DevKit 2. It is not manufactured or supported as a product; hardware questions go to Discord.

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Overview

DevKit 2 is a necklace-form-factor dev kit built on the Seeed Xiao nRF52840 (Sense). It streams audio to the Omi app over BLE and, unlike DevKit 1, can record standalone to a removable microSD card (FAT/exFAT; bring your own card) and sync through the app afterwards. It has a small speaker and a 250 mAh 1S LiPo battery charged over USB-C.
Standalone recordings still need the Omi app for transcription. The device records audio; processing happens on the phone or backend.

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Button, LEDs, and power

The firmware source is the authority for device behavior in this table (omi/firmware/devkit/src/button.c, main.c): There is no power switch and no push-to-talk mode: a long hold always means power off. Boot briefly blinks red, green, blue, then white.

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Install firmware

OTA via the Omi app

The default path: pair the DevKit in the app and accept the update prompt (Nordic DFU over BLE)

UF2 drag-and-drop

Double-click RST, drop the .uf2 on the XIAO-SENSE drive

Pre-built firmware

GitHub Releases tagged DK2

Compile from source

nRF Connect SDK v2.7.0, preset build_xiao_ble_sense_devkitv2-adafruit

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Testing device storage over BLE

Standalone recordings land on the microSD card as audio/a01.txt, audio/a02.txt, and so on. The app imports them automatically when it reconnects. To read or clear them yourself, use the storage service: Commands are 6 bytes, [command, file, offset_1, offset_2, offset_3, offset_4], with a big-endian byte offset. A 2-byte [command, file] form leaves the offset at zero. File numbers start at 1. Replies arrive as notifications on the command characteristic. A one-byte notification is a status. Anything longer is audio, up to 440 bytes per notification: Helper scripts for discovery, listing, downloading, decoding, and deleting live in omi/firmware/scripts/devkit/. Button events over the button characteristic are 1 single tap, 2 double tap, and 5 release. A long press powers the device off and is not reported.

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Getting a DevKit 2

DevKit 2 is no longer sold. For new hardware see Omi (CV1) or build a DevKit 1 from parts.

Omi (CV1)

Current consumer hardware

DevKit 1

The first dev kit (also legacy)

Flash firmware

Update and recovery flows

BLE Protocol

The device ↔ app protocol