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FreeTRX/MANUAL.md
Marcus Kida 5ae4fa70bd docs: add MANUAL.md user guide (OpenGD77 vs FreeTRX features tagged) 
New user-facing feature & usage guide covering inherited OpenGD77 features and
FreeTRX additions, each marked [FreeTRX] or [OpenGD77]. Documents the spectrum
scope (VFO sweep, hold #), channel add/delete, mute, screen dimming, the S-meter
and 7-seg font, plus a button reference. Linked from the README.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-07-10 13:01:01 +02:00

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FreeTRX — User Manual

Feature and usage guide for FreeTRX (a fork of OpenGD77) on the TYT MD-UV380 / Retevis RT-3S and Baofeng DM-1701 / Retevis RT-84.

How to read this manual

Each feature is tagged so you can tell what is unique to FreeTRX and what is inherited from upstream OpenGD77:

  • 🟢 [FreeTRX] — new or noticeably changed in FreeTRX.
  • ⚪ [OpenGD77] — inherited from upstream OpenGD77, documented here for convenience. For exhaustive coverage of upstream behaviour, see the official OpenGD77 user guide.

Most day-to-day operation (VFO/Channel, FM, DMR, scanning, hotspot, CPS sync) is standard OpenGD77. This manual focuses on how to reach each feature and marks clearly what FreeTRX adds or changes.

Buttons at a glance

The MD-UV380 / RT-3S has PTT, SK1 (upper side key), SK2 (lower side key), the top / orange button, and a keypad with green (✓ / menu), red (✗ / back), arrows, 0–9, * and #.

Control Action
Green Menu / confirm
Red Back / exit
Top / orange button Open the quick menu (VFO or Channel) — ⚪ [OpenGD77]
SK1 (hold) Show frequency / secondary info
SK2 (hold) Modifier for other keys
SK2 (short tap) Toggle mute on VFO/Channel — 🟢 [FreeTRX]
SK2 (extra-long) Monitor / open squelch — ⚪ [OpenGD77]
SK1 + SK2 Reverse repeater — ⚪ [OpenGD77]
# (hold, VFO) Toggle the spectrum scope — ⚪ [OpenGD77]
SK2 + green (Channel) Open Channel Details editor — ⚪ [OpenGD77]

Display & UI

Segmented S-meter — 🟢 [FreeTRX]

The signal meter under the top status bar is drawn as discrete blocks: 9 green blocks for S1–S9 (4 dB each) and 6 red blocks for S9+10…+60 (10 dB each), with a scale-label row beneath (S1 S3 S5 S7 S9 / +20 +40 +60). The leading block fills proportionally.

7-segment "LED" frequency font — 🟢 [FreeTRX]

On the VFO and the SK1-held frequency view, the frequency is rendered in a 7-segment "LED" style (lit segments only). "MHz" matches the frequency colour (green on RX, red on TX).

Screen dimming — 🟢 [FreeTRX]

Optionally dims the backlight after inactivity to 100 / 50 / 30 / 15 % of the configured brightness (only in Auto backlight mode). Any activity restores full brightness. Set it in Menu → Options → Display Options → Screen Dim.

Main-menu icons — 🟢 [FreeTRX]

Each top-level menu entry has a small icon next to it.

Mute indicator — 🟢 [FreeTRX]

While muted, a bold "M" appears in the status bar (just left of the battery) and the red LED flashes (0.5 s every 2 s). See Mute below.

Audio

One-tap mute — 🟢 [FreeTRX]

  • A short tap of SK2 on the VFO/Channel screen toggles the speaker mute on/off. (Exception: while a DMR QSO is on screen, SK2 keeps its "set TX talkgroup to the incoming one" role.)
  • Turning the volume knob fully down also counts as muted.
  • Mute is shown by the "M" indicator and the flashing red LED (above).
  • Mute is also available in the Channel/VFO quick menu.

Operating

VFO & Channel modes — ⚪ [OpenGD77]

Switch between direct-frequency VFO mode and stored Channel mode with the mode toggle. Most operating happens here.

Spectrum scope (VFO sweep) — ⚪ [OpenGD77]

A real-time signal-strength-vs-frequency graph centred on the VFO frequency.

  • Enter/exit: in VFO mode, hold # (long press). Hold # again to leave.
  • Left / Right: move the centre frequency across the band.
  • Up / Down: change the sweep span / step (zoom in / out).
  • SK2 + Up/Down: adjust gain; SK2 + Left/Right: adjust the noise-floor reference (how the trace fills the screen).
  • The gain / noise-floor / step settings are remembered.
  • The scope is VFO-only (not available in Channel mode).

Scanning — ⚪ [OpenGD77]

Channel and VFO scanning with hold/pause behaviour, per the upstream OpenGD77 controls.

Quick menu — ⚪ [OpenGD77] (with 🟢 [FreeTRX] additions)

Press the top / orange button to open the quick menu for the current screen (VFO or Channel). It holds filters (FM/DMR), Talkaround, Roaming, Mute, VFO↔Channel copy, and — on the Channel screen — the FreeTRX new channel / Delete Channel items (see below).

Channels & zones

Channel Details editor — ⚪ [OpenGD77]

Edit an existing channel's parameters (name, frequencies, tones, power, bandwidth, timeslot, colour code, groups, …). From the Channel screen, press SK2 + green. Press green to save.

Create & delete channels on the radio — 🟢 [FreeTRX]

No PC/CPS required. Open the Channel quick menu (top/orange button) and scroll to the bottom:

  • New channel — creates a blank 145.500 MHz FM channel in the first free slot, adds it to the current zone, and opens Channel Details to edit it. The new channel is immediately selectable in the zone.
  • Delete Channel — deletes the selected channel after a confirmation (green confirms, red cancels). It is also removed from every zone that referenced it. The last remaining channel can't be deleted, and read-only/APRS channels are protected.

Back up your codeplug (via the CPS) before bulk edits — changes are written straight to the radio and there is no on-device undo.

Zones — ⚪ [OpenGD77]

Select zones from Menu → Zone. The virtual All Channels zone lists every channel. (On-radio zone editing is planned for a future FreeTRX release.)

DMR

DMR operation — ⚪ [OpenGD77]

Talkgroups/contacts, timeslots, colour codes, RX groups, and hotspot mode, all per upstream OpenGD77. The AMBE voice codec is merged in at flash time (see TOOLS.md).

DMR reliability fix — 🟢 [FreeTRX]

FreeTRX resolves a hard-fault (freeze needing a battery pull) on the DMR path that affected recent self-built OpenGD77 revisions — the codec is called through C function pointers instead of inline assembler that modern GCC miscompiled.

About & versioning — 🟢 [FreeTRX]

Menu → Firmware info shows the FreeTRX version (semantic versioning, e.g. FreeTRX v0.4.0) alongside the git commit ID. Pre-1.0 builds are published as pre-releases. See CHANGELOG.md for the full history.

Building, flashing and tools are covered in TOOLS.md; the project overview is in README.md.