The UI

Replay transmits captured IQ files (.C16 or .C8 or .CU8) over the air. Files can be played individually or organized into a playlist (.PPL) for sequential playback with optional delays between entries.

Display

• Line 1: Name of the currently loaded capture file.
• Line 2: Frequency (editable) and sample rate of the current track. Two stacked progress bars on the right — the top shows position within the playlist, the bottom shows transmit progress of the current file.
• Line 3: Duration of the current track in seconds. TX gain (0–47), TX amp (0/14), Loop checkbox (default: on), and the play/stop button.
• Line 4: Current track number / total tracks (e.g. 1/2) on the left, current playlist filename on the right.

A live waterfall is displayed below the controls during transmission.

Controls

• ◄ / ►: Navigate to the previous or next track in the playlist.
• 📄 (Add file): Opens the file picker to select a .C16 or .C8 or .CU8 capture file and append it to the end of the playlist.
• 🗑 (Delete): Removes the currently selected track from the playlist.
• 📂 (Open): Opens the file picker to load a .PPL playlist file. This replaces the current playlist.
• 💾 (Save): Saves the current playlist to the active .PPL file.
• Loop (checkbox, default: on): When enabled, the playlist restarts from the beginning after the last track finishes.
• ▶ / ■: Start or stop playback.

The frequency field is editable per-track and is not saved to the playlist file.

Playing a Single File

When the app opens with an empty playlist, the Add file button is automatically focused. Press it, select a .C16 or .C8 or .CU8 file, and the play button receives focus immediately — allowing fast two-button playback.

You can also open a capture or playlist file directly from the File Manager app, which will launch Replay with that file pre-loaded.

Playlist Files

Playlist files use the extension .PPL and are stored in the PLAYLIST/ directory on the SD card. They are plain text, comma-delimited files.

Format:

ABSOLUTE_PATH_TO_FILE,DELAY_MS
# Comment lines starting with # are ignored

The delay (in milliseconds) is optional. If omitted, no pause is inserted between tracks.

[!WARNING] The pre-delay is implemented as a blocking sleep on the UI thread. Setting a long delay will cause the device to appear frozen for that duration. There is no way to interrupt it other than resetting the device.

Example:

# Playlist file
/SAMPLES/TeslaChargePort_US.C16
/SAMPLES/TeslaChargePort_EU_AU.C16,100

This plays the US file, then pauses 100 ms, then plays the EU/AU file.

When a new capture file is added to an empty playlist, a new playlist file is created automatically with the name PLAY_XXXX.PPL in PLAYLIST/. The playlist is not saved to disk until you press the Save button.

Metadata fallback: If a capture file has no matching .TXT metadata file, the current transmit frequency and a sample rate of 500,000 Hz are assumed.

Settings Persistence

Settings are saved to tx_replay.ini.