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Fabian Plaimauer edited this page Jul 23, 2026 · 1 revision

Select Eyes to Detect (enabled_eye)

"Select eyes to detect" (Both / Left only / Right only) is a genuine, persistent device-level property — the same platmod-property family as the display area — not merely a calibration input. Source of truth: crates/tobii-protocol/src/frame.rs (op codes), crates/tobii-protocol/src/commands.rs (EnabledEye, payload/parse), crates/tobii-usb/src/connection.rs (get/set_enabled_eye), memory note et5-enabled-eye-op.

Ops

Op Dec Name Request payload Response
0xc62 3170 get_enabled_eye empty 00 00 02 00 00 00 04 00 00 00 0N
0xc58 3160 set_enabled_eye 00 00 02 00 00 00 04 + BE32(value) ack

SET (0xc58) is a LOWER op code than GET (0xc62) — the inverse of the display-area and calibration convention. This is real; do not "correct" it.

Msg-class/tag 0x51 like display-area, 3 s timeout. Both are version-gated on [dev+0x1a0] >= 0x10007; older firmware returns NOT_SUPPORTED (err 2), and get_enabled_eye then returns None. [CODE-VERIFIED] op codes / gating (native disasm); [CONFIRMED] live that both ACK and round-trip.

Wire enum (1-based)

1 = LEFT      2 = RIGHT      3 = BOTH        (0 folds to BOTH)

This is the C-API tobii_enabled_eye_t {LEFT=0, RIGHT=1, BOTH=2} plus 1 — the response integer is NOT the C-API value; remap with C-API = wire − 1. EnabledEye::{Left,Right,Both} encodes exactly 1/2/3. [CONFIRMED] — commands.rs::to_wire/from_wire, enabled_eye_wire_round_trips.

The hardware-captured BOTH GET response is:

00 00 02 00 00 00 04 00 00 00 03
                        ^^^^^^^^^^ BE32 value = 3 (BOTH)

parse_enabled_eye reads the trailing BE32. [CONFIRMED] — commands.rs::enabled_eye_payload_and_parse_match_device, connection.rs::get_enabled_eye_parses_device_response.

Enum landmine: this property's wire enum (1=L,2=R,3=B) is a different numbering from the cal_add_point (0x408) eye argument (0=both,1=L,2=R, see Calibration). Same integer ≠ same eye across contexts. Never share a constant between the two.

Semantics: persists, but takes effect only on (re)calibration

Hardware-verified 2026-07-20 [CONFIRMED] (memory et5-enabled-eye-op):

  • A standalone SET is acked and PERSISTS across reboot — a fresh-session GET returns the value that was set.
  • BUT a standalone SET does NOT change live detection. Both eyes keep reporting validity == 0 in the gaze stream regardless of the setting.
  • The property only takes effect when the tracking model is rebuilt, i.e. via tobii_calibration_start(enabled_eye), which happens on (re)calibration. The vendor app never SETs it standalone; it persists the choice host-side per profile and re-applies by recalibrating.

Consequence: setting enabled_eye alone stores a preference but the tracker keeps detecting both eyes until a calibration is run. Whether a standard calibration (which drops the eye arg on the wire, Calibration) is enough to apply the selection is unresolved — a Windows-VM capture of toggling Left/Right/Both settles it. [HYPOTHESIS].

API / CLI

Connection::get_enabled_eye() -> Option<EnabledEye>, set_enabled_eye(eye) -> bool (acked?). CLI: tobii enabled-eye [both|left|right] — sets (if an arg is given) then reads back. [CONFIRMED] — connection.rs, main.rs::enabled_eye_cmd.

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