libg2sdrk

Kotlin driver for the ANAN-G2 / Saturn amateur-radio SDR transceiver, speaking the openHPSDR Protocol 2 over UDP. Pure Kotlin — no NDK, no native libraries, no root. Built for Android but the wire codec is Android-free and JVM-testable.

Maintained by Isak — PU3IAR. Brought to you by id.qsl.br, a platform with tools for amateur radio operators. YouTube: @qraisak

Features

• G2Protocol — the openHPSDR Protocol 2 frame codec, free of any Android dependency and unit-tested on the JVM:
  • UDP discovery (board id, MAC, gateware, DDC count) and the General / RX-specific / TX-specific / high-priority command packets.
  • RX: DDC IQ parsing (24-bit big-endian, 238 samples/packet, source ports 1035+), for 1 or 2 receivers, at 48/96/192/384 kSps.
  • High-priority C&C: run/MOX, DDC and DUC frequencies (Hz), TX drive, open-collector outputs, step attenuators, and the Saturn Alex filter words — four 16-bit registers (TX LPF + antenna + T/R; RX1/RX2 band-pass) computed from frequency, since the gateware never auto-selects filters.
  • TX: 240-sample 24-bit IQ packets for the fixed 192 kSps DUC, and telemetry decode (PTT/dot/dash, PLL lock, ADC overload, exciter / forward / reverse power, supply voltage).
• TxInterpolator — polyphase FIR (Blackman-windowed sinc) expanding the 48 kSps modulator IQ to the 192 kSps DUC rate with images below −60 dBc.
• G2Client — UDP transport and streaming lifecycle:
  • LAN discovery (or a fixed radio IP), RX accumulation into display blocks and a power spectrum, delivered through the same callback contract as the sibling clients so a host app can drive any device.
  • A wall-clock-paced TX sender (800 packets/s) that only consumes whole packets of queued audio, and a keepalive that satisfies the radio's 1-second activity watchdog when armed.

Validation

The wire contract is pinned by JVM tests written against two independent ground truths: the Thetis reference client (ChannelMaster/network.c) and the radio-side p2app server that runs inside the ANAN-G2 (Saturn/sw_projects/P2_app), including the p2app reference values for the Alex filter registers.

Credits and references

Faithful port of the reference implementations and the openHPSDR documentation:

• Saturn / ANAN-G2 project (hardware, FPGA, p2app radio-side server) — Laurence Barker (G8NJJ) and contributors: https://github.com/laurencebarker/Saturn
• Thetis console (reference Protocol 2 host client) — the Thetis maintainers and the openHPSDR community: https://github.com/ramdor/Thetis
• openHPSDR Ethernet Protocol (Protocol 2) specification — the openHPSDR project and TAPR.

License

GNU General Public License v2 or later — see LICENSE. Kotlin port © 2026 Isak Ruas isakruas@gmail.com.