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 map the config tool fills in when you pick the X18, and it matches the bundled model file below. 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
CH16	SI	2‑position switch
CH17	SJ	2‑position switch
CH18	LS	Left side slider
CH19	RS	Right side slider

Firmware boot vs. config tool — the firmware itself only boots CH1–CH15 (sticks, S1/S2, the matrix, and SA–SH); SI, SJ and the LS/RS sliders start at channel 0 until a config is loaded. Selecting the X18 in the config tool pre‑assigns them to CH16–CH19 as shown above, and the bundled model file outputs them there too. Any control you don't use simply stays at channel 0.

X20 extras — selecting the Twin X20 keeps the X18 map and adds the middle slider S3 → CH20. With the optional 3‑axis gimbal upgrade, the twist axes land on J5 → CH21 and J6 → CH22, and the two stick‑click momentary buttons ride matrix slots 19/20 on CH7.

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 physical 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. The same matrix channel also carries up to 15 user‑defined "logical buttons" — extra PWM bands not tied to any control on the TX graphic — which you assign in the config tool's Logical Buttons panel, so the effective button count goes well beyond the physical controls.

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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 to < 1401 = Mode 2 (mid), ≥ 1401 = Mode 3 (up).

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