FreeTRX/MANUAL.md

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.

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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]
Green (hold)	Open Messages (DMR SMS) — 🟢 [FreeTRX]

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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.

Shut-off animation — 🟢 [FreeTRX]

Powering off collapses whatever is on screen towards the middle — squeezed to a line, then a dot — like an old CRT switching off, in place of the "Power Off" message. (Once the animation starts, the power-off is committed.)

Theme presets — 🟢 [FreeTRX]

Pick a colour theme on the radio at Menu → Options → Display Options → "Theme" (◀/▶ to change; the screen updates live):

• Custom — the theme edited via the CPS or the on-radio colour editor (default).
• BASIC 80s — a Commodore-64 look (light blue on blue).
• Terminal — a green terminal (green-on-black at night, black-on-green by day).
• Vertexic — amber/orange (black-on-amber by day, amber-on-black at night).
• Red — black-on-red by day, red-on-black at night.
• Neon 80s — an 80s-synthwave palette with several neon colours (cyan, magenta, violet, green, yellow) across the UI over a dark background.
• Pride — the background is painted as a rainbow pride flag; body text is black over the stripes, and the menu title, header and notifications use white boxes so they stay readable. (Text drawn directly over the brightest stripes has lower contrast than a solid-background theme — that's inherent to a rainbow background.)

Editing colours in the CPS only affects Custom; the built-in presets are fixed. Every element (S-meter, frequencies, menus) follows the selected theme.

Mute indicator — 🟢 [FreeTRX]

While muted, the red LED flashes (0.5 s every 2 s). See Mute below.

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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.

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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]

There are no scan lists. Unlike the vendor CPS, OpenGD77 scans the channels of the currently selected zone — so a zone is the scan list. To scan a particular set of channels, put them in a zone and select it. The All Channels virtual zone scans every channel in the codeplug.

• Start/stop: long-press UP on the Channel or VFO screen (RED stops).
• Exclude a channel: Menu → Channel details (or SK2 + green on the Channel screen) → Zone Skip (skipped when scanning a normal zone) and All Skip (skipped when scanning All Channels).
• Settings: Menu → Options → Radio options → Scan delay, Scan dwell, Scan mode (Hold / Pause / Stop) and Scan On Boot.

Note: in the codeplug these two skip flags reuse the old "Auto Scan" and "Lone Worker" bits, so a vendor CPS may label them differently — set them on the radio to avoid confusion.

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).

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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.)

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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).

Contacts list — 🟢 [FreeTRX]

Menu → Contacts lists all contact types together under the title "Contacts" (instead of defaulting to the group filter). Press # to cycle the filter: all → groups → private → all-call → all.

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.

Text messages (SMS) — 🟢 [FreeTRX]

Send and receive DMR text messages, compatible with BrandMeister, hotspots and OEM radios (Motorola TMS format on transmit; TMS and Anytone/"DMR standard" decoded on receive).

Open it from Menu → Messages, or hold GREEN on the channel/VFO screen. The hub offers New message, Inbox, Sent, Quick text and Options.

Composing: in the recipient field, either type the destination DMR ID with the number keys and press DOWN to move on to the message, or press GREEN to pick a recipient from your private-call DMR contacts (selecting one drops you straight into the message text). Type up to 160 characters with multi-tap on the keypad (LEFT/RIGHT move the cursor, SK2+LEFT deletes), then press GREEN to send. Sending only works on a DMR channel; progress is shown as notifications ("Sending", "Sent", "Delivered"). With Wait for ACK enabled (default), a missing delivery report pops up a resend prompt.

Receiving: a popup with a chime shows the sender and a preview — GREEN opens the message, SK2+GREEN starts a reply, RED dismisses. The inbox and sent box keep the last 8 messages each and survive power cycles; unread messages are marked *. In a message view, GREEN replies (inbox) or re-edits/resends (sent), SK2+RED deletes. The radio automatically answers delivery-report requests from other radios.

Quick texts: up to 8 editable templates (GREEN uses one in a new message, SK2+GREEN edits, SK2+RED deletes).

Options: Wait for ACK (delivery confirmation) and My ID only (ignore messages not addressed to your DMR ID). PTT is locked out for the second or two a message is on air; hotspot mode is unaffected.

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About & versioning — 🟢 [FreeTRX]

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

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