# id5100 — Decisions

Format: `YYYY-MM-DD: <decision> — <why>`

- 2026-06-14: Pure-stdlib `termios` instead of pyserial — system Python is PEP-668
  externally-managed; per the escalation-brake rule, `--break-system-packages` for
  one dependency is the wrong trade. `termios` is zero-install and reusable.
- 2026-06-14: Layered as codec (`civ.py`) / transport (`radio.py`) / CLI (`cli.py`)
  — the codec is pure and unit-testable; web UI / HA-MQTT front ends bolt onto the
  transport without touching byte plumbing.
- 2026-06-14: TDD the codec against the real probe capture (`00 00 30 47 01` ↔
  147.300000 MHz) — gives a hardware-true vector, not a made-up one.
- 2026-06-14: Cable lands on **[SP2]** (= CI-V), 9600 baud, addr 0x8C — verified
  live, not assumed.

- 2026-06-14: Web panel = stdlib `http.server` + single `panel.html`, no framework
  — keeps the no-deps promise; the UI is one self-contained file. One shared `Radio`
  guarded by a lock (CI-V is half-duplex; concurrent transactions would interleave).
- 2026-06-14: `transact()` returns as soon as the radio's reply frame parses instead
  of always burning the full timeout — dropped a full status poll from ~3.6s to ~0.2s,
  making a ~1 Hz live S-meter poll viable.
- 2026-06-14: Aesthetic = industrial instrument faceplate (amber VFD via DSEG7 font,
  LED S-meter, illuminated mode buttons) — matches the radio-gear domain and the
  Sethian dark/orange brand. Verified by headless screenshot.

## Deferred / Rejected

- **Full software control-head replica** — rejected: the detachable head talks a
  proprietary, undocumented bus to the main unit; CI-V exposes operating functions
  only (no menu/LCD mirror). Not worth reverse-engineering.
- **pyserial** — rejected (see above).
- **DV mode set** — deferred: 0x17 unverified on this radio; don't ship set_mode('dv')
  as trusted until confirmed against the manual's CI-V table or the live rig.
- **RS-MS1A data-jack protocol (D-STAR DR/callsign/messaging)** — out of scope for
  this CI-V layer; separate effort if wanted.