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Overview

Two areas to test on DevKit 2: SD card storage (offline audio recording) and button behavior (tap events via BLE).
Never remove the SD card while the device is on. It is not hot-swappable. Use the safe removal process described below.

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SD Card Storage

When the device is disconnected from the phone (LED is red), audio data is written to the SD card instead of streaming over Bluetooth.

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SD Card Commands

Commands are sent as 6-byte packets: [command, file_number, offset_byte0, offset_byte1, offset_byte2, offset_byte3] Example: Read file 1 starting at byte 255:

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Response Codes

If you don’t receive code 100 or 200, the command was not completed.

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Testing Process

Prerequisites: Python packages from requirements.txt, plus ffmpeg and opus for audio decoding. The test scripts live in omi/firmware/scripts/devkit/.
Run these scripts in order:

Discover Devices

Run discover_devices.py to list all nearby Bluetooth devices. Look for “Omi” or “Omi Devkit 2” and note the device ID.

Check File Sizes

Run get_info_list.py — replace the device_id value with your device ID. This lists the size of each audio file on the SD card.

Download Audio

Run get_audio_file.py — replace the device_id value with your device ID. Audio data streams to my_file.txt in the current directory.

Decode Audio

Run decode_audio.py to convert the downloaded data into a WAV file. If successful, you’ll have a playable recording of what was spoken near the mic.

(Optional) Delete Audio

Run delete_audio_files.py — replace the device_id value with your device ID. This clears audio data from the specified file.

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Safe SD Card Removal

1

Reset the device

Double-tap the reset button inside the kit
2

Remove the SD card

Remove the card to inspect contents on your computer
3

Reinsert and restart

Put the SD card back and tap the button to restart

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Device Behavior

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App-Side SD Card Import

When the device connects to the app with stored audio:
  1. A green banner appears showing estimated download time
  2. Tap the banner (or go to Settings → Device Settings → Storage) to open the import screen
  3. Press the download button to start importing — a progress bar shows completion
The green banner only appears for DevKit 2 devices. DevKit 1 devices do not support SD card import.

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Button Events

After connecting to the BLE notification service, these events fire: Verify that each physical action sends the correct BLE packet.

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Known Issues

Some devices create an empty a01.txt file, preventing audio from being written.Fix:
  1. Delete the audio file
  2. Press the reset button to reboot
  3. The device will auto-generate the required files on startup