Transmitter Setup

Transmitter Setup

NaviCore decodes a standard FrSky SBUS stream. It ships with metadata for three transmitter models, and a ready‑made model file for the X18 so you don't have to build the channel map by hand.

Pick your model in the config tool under Config → Transmitter. The model drives which SVG is shown, the default channel assignments, the control labels, and which controls appear in the calibration wizard. (The firmware itself is model‑agnostic — every control is gated on its assigned channel, so unused controls just sit at channel 0.)

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Supported models

Model	Notes
FrSky Tandem X18 (default)	Full‑size. 10 switches, 2 knobs (S1/S2), 2 side sliders (LS/RS).
FrSky Twin X‑Lite	Handheld. 6 switches (SE/SF momentary), 2 knobs, no sliders, 4 face buttons.
FrSky Twin X20	X18 layout plus an S3 middle slider and, with the optional 3‑axis gimbal upgrade, J5/J6 twist axes and two stick‑click momentary buttons (matrix slots 19/20). Enable via the 3‑axis gimbals checkbox on the Transmitter tab.

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Default channel map (X18, Mode 2)

This is the layout the firmware defaults to. You can override any of it per‑control via calibration, so a custom mixer setup still works.

Channel	Control	Role
CH1	J1	Aileron — right‑stick X
CH2	J2	Elevator — right‑stick Y
CH3	J3	Throttle — left‑stick Y
CH4	J4	Rudder — left‑stick X
CH5	S1	Rotary knob
CH6	S2	Rotary knob
CH7	Button matrix	All matrix buttons, multiplexed (see below)
CH8	SA	3‑position switch
CH9	SB	3‑position switch
CH10	SC	3‑position switch
CH11	SD	3‑position switch
CH12	SE	3‑position switch — mode selector by default
CH13	SF	2‑position switch
CH14	SG	3‑position switch
CH15	SH	2‑position switch

Disabled by default (channel 0 — assign in the tool if your build has them): SI, SJ, sliders LS/RS, X20 S3 slider, X20 J5/J6 twist axes.

The button matrix (CH7) carries every physical button as a distinct PWM band — pressing a button drives CH7 to that button's value, and NaviCore decodes which one. That's why a single channel can serve ~20 buttons. The default band table (B1–B6, the T1–T6 trims as Left/Right or Up/Down, and the X20 stick‑clicks) is built from measured X18 values; calibrate to lock the bands to your radio.

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Loading the X18 model file

The repo bundles a matching transmitter model so your radio outputs exactly the channel map above:

1. Find model/r2 web gui.bin in the repository (~2.4 KB).
2. Copy it to the MODELS/ folder on your transmitter's SD card.
3. On the radio, open the model select screen and load it.

This sets up the stick/switch/knob channel assignments and the CH7 button‑matrix mixer. If you use your own model, that's fine — just calibrate in the config tool so NaviCore learns your channels and matrix bands.

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Modes

A 3‑position switch selects one of three modes (Mode 1 / 2 / 3). Each mode has its own complete set of button mappings — so the same physical button can do different things in each mode, tripling your control surface. The mode switch defaults to SE (CH12) and can be reassigned (or disabled) under the config tool's binding settings.

• Switch position thresholds (SBUS counts): < 582 = Mode 1 (down), 582–1401 = Mode 2 (mid), > 1401 = Mode 3 (up).

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