Continuously rotating file carousel over FSK radio. Transmit files from an inbox folder; receive and reassemble them on the other end. Built for HackRF TX and RTL-SDR RX on Windows (MSYS2/MinGW64).

• Continuous carousel — files cycle endlessly, smallest-first
• Direct FSK at user-selectable baud rates (default 12500)
• AFSK mode (Bell 202: 1200/2200 Hz)
• Callsign tagging — receiver identifies the transmitting station
• Qt6 GUI for both TX and RX with progress bars, cycle tracking, kbps
• Graceful recovery — receiver picks up partial files on next rotation
• PID CAROUSEL STATUS — real-time carousel position embedded in every data packet

pacman -S mingw-w64-x86_64-gcc mingw-w64-x86_64-hackrf \
          mingw-w64-x86_64-rtl-sdr mingw-w64-x86_64-qt6-base
make

Outputs go to build/. DLLs (libhackrf.dll, librtlsdr.dll, Qt6 DLLs, etc.) and the platforms/ folder must live next to the EXEs.

build/file_tx.exe -F inbox -f 145100000 -b 12500 -k -c MYCALL

build/file_rx.exe -f 145100000 -b 12500 -k -o outbox

Received files land in outbox/. Press Ctrl+C to stop.

build/file_tx_gui.exe
build/file_rx_gui.exe

Both GUIs show per-file progress bars, carousel position, kbps, and elapsed time.

Sent at the start of each file and every 100 chunks within large files.

type(1) | cs_len(1) | callsign(N) | file_count(1) | [id(1) | name_len(1) | name(N) | size(4)]*

type(1) | file_id(1) | chunk_id(2) | total_chunks(2) |
carousel_total(2) | carousel_pos(2) | data(≤500) | CRC(2)

• file_id: unique ID per file in this carousel
• chunk_id: 0-based chunk index
• total_chunks: chunks in this file
• carousel_total: total chunks across all files in cycle
• carousel_pos: current position (0-based, wraps)

Each chunk carries up to 500 bytes of file data. CRC-16 protects the payload. HDLC framing with NRZI encoding and bit-stuffing.

1. TX scans the inbox folder, sorts files smallest-first
2. FILE_LIST packet announces available files and callsign
3. Files are chunked into 500-byte pieces, each wrapped in FILE_DATA + HDLC
4. Data modulates as direct FSK (±deviation) or AFSK (mark/space tones)
5. RX demodulates, validates CRC, writes chunks to .part temporary files
6. On file completion, .part renamed to final filename
7. Carousel repeats — partial files fill in gaps with each rotation

• Direct FSK: -k mode, 12500 baud, ±6250 Hz deviation, 2 Msps
• AFSK: Bell 202, 1200 baud, 1200/2200 Hz mark/space, 2.4 Msps

FSK/
  *.cpp, *.h, Makefile   — source
  build/
    *.exe, *.dll         — binaries & runtime
    platforms/qwindows.dll
    inbox/               — files to transmit
    outbox/              — received files