feat(rc_smoothing): update filter dropdown for 1EURO; add beta spinner (semver 0.5.0)

[nerdCopter]

AI Generated issue-ticket

Companion to emuflight/EmuFlight#1247 (1€ adaptive RC smoothing filter).

Gate all changes on firmware semver 0.5.0 (exact version TBD at firmware PR merge — update when confirmed).

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Firmware-only testing (CLI, no configurator changes required)

No configurator changes are needed to flight-test the firmware PR. Enable 1EURO with two commands:

set rc_smoothing_type = FILTER
set rc_smoothing_input_type = 1EURO
set debug_mode = RC_SMOOTHING
set rc_smoothing_debug_axis = ROLL
save

Optional — only tune beta if needed (default works for most pilots):

set rc_smoothing_1euro_beta = 5   # default; increase to 8-10 for 50 Hz links only

fc_min, fc_max, and deriv_hz are CLI-only developer parameters — not MSP-exposed, no configurator UI required.

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One new MSP byte

N+2 is repurposed from a dead/reserved byte (was rc_smoothing_derivative_cutoff in master, unused) to carry rc_smoothing_1euro_beta. All other bytes in the RC smoothing block are unchanged from master.

N+4 remains a dead/reserved byte — fc_min is CLI-only by design.

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Problem with current configurator UI

The configurator currently shows controls that are wrong or misleading when 1EURO is selected:

• N+1 → "input cutoff (Hz)" spinner — correct for PT1/PT2; ignored by firmware when 1EURO is active
• N+2 → "derivative cutoff (Hz)" spinner — mislabels beta as a cutoff Hz value for 1EURO users
• N+4 → "derivative type" dropdown — dead byte; this control should be removed entirely
• Filter dropdown — shows BIQUAD (index 1) and PT4 (index 4); both are gone from firmware

Without fixes a pilot selecting 1EURO will see their beta value displayed as "derivative cutoff Hz" with no way to understand what it means.

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Required changes (semver ≥ 0.5.0)

1. RC smoothing filter dropdown

Index	Old label	New label	Action
0	PT1	PT1	no change
1	BIQUAD	1EURO	rename
2	PT2	PT2	no change
3	PT3	PT3	no change (was removed in an earlier edit, now restored)
4	PT4	—	remove

Show the legacy list on firmware older than 0.5.0 to avoid breaking existing configs.

2. Remove N+4 "derivative type" control

The N+4 derivative type dropdown is a dead byte. Remove it from the UI entirely.

3. Show/hide controls by filter type (firmware ≥ 0.5.0)

When filter = 1EURO:

• Hide N+1 "input cutoff" spinner (ignored by firmware)
• Hide N+2 "derivative cutoff" spinner
• Show 1€ Beta spinner (reads/writes N+2):

Label	Byte	Range	Default
1€ Beta (×0.001)	N+2	1–20	5

When filter = PT1, PT2, or PT3:

• Show N+1 "input cutoff" spinner as normal
• Hide the 1€ Beta spinner (N+2 must not be shown as "derivative Hz" for these types)

4. Beta spinner detail

Beta is stored as a uint8 (1–20). Displayed value is the raw integer; firmware divides by 1000 on read. A spinner labeled "1€ Beta (×0.001)" with range 1–20 and default 5 is sufficient.

[nerdCopter]

AI Generated comment

Help tip text — UI copy spec

Filter dropdown — 1EURO entry tooltip

Adaptive filter — cutoff frequency rises automatically with stick speed, then returns to a low floor at rest. Recommended for most pilots.

1€ Beta spinner tooltip

Controls how aggressively the filter opens during fast inputs. Default 5 suits most flying styles. Lower (3) for smoother cinematic feel; higher (8–10) for racing or fast freestyle.

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CLI-only parameters — for PR description and release notes only, no UI required

Parameter	Default	Note
rc_smoothing_1euro_fc_min	0 (auto)	Auto scales with RC link rate — leave at 0. See PR for per-protocol values.
rc_smoothing_1euro_fc_max	200	Safety ceiling only — irrelevant at default beta.
rc_smoothing_1euro_deriv_hz	10 (= 1.0 Hz)	Per 1€ spec — do not change.

These are intentionally not in the Configurator UI. CLI users who need them will find them in the firmware PR description.

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Beta by flying style — for release notes / Configurator help text

Style	Beta
Cinematic / smooth	3
General freestyle (default)	5
Racing / fast freestyle	8–10