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docs(g6_03): trial-params (0x08) re-layout — gain int16 + duration field #65

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docs(g6_03): trial-params (0x08) re-layout — gain int16 + duration field #65

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11 changes: 5 additions & 6 deletions docs/development/g6_03-controller.md
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Original file line number Diff line number Diff line change
Expand Up @@ -270,7 +270,6 @@ G6 collapses G4's two wires (host→Host.exe and Host.exe→controller) into one
| Opcode | G4 | G6 | Note |
|---|---|---|---|
| `0x01` | DISPLAY_RESET (reset FPGA display) | SYSTEM_RESET (reboot MCU) | Deliberate repurpose; a G4 client's display-reset triggers a full reboot + link drop. |
| `0x08` | trial-params: `gain` int16 + trailing `runtime` | trial-params: `gain` int8, no runtime, `rate` int16 | Same intent, different payload layout; G4 12-byte frame misparses. Reconciliation open. |
| `0x32` | stream-frame with `aox/aoy` header bytes (also dual-used as setAO) | stream-frame, 3-byte header, no `aox/aoy` | Different header; G4 `setAO`-via-`0x32` overload absent (G6 uses `0xA0`). |

### Per-command wire formats
Expand Down Expand Up @@ -336,7 +335,7 @@ Recognized only to produce an explicit rejection. Grayscale mode is inferred fro

Selects the display mode (2/3/4), opens the named SD pattern, and arms the refresh timer.

**Command:** `[len, 0x08, mode, pat_id_lo, pat_id_hi, rate_lo, rate_hi, gain, init_lo, init_hi, …]`
**Command:** `[len, 0x08, mode, pat_id_lo, pat_id_hi, rate_lo, rate_hi, init_lo, init_hi, gain_lo, gain_hi, dur_lo, dur_hi]`

Payload bytes after the command byte:

Expand All @@ -345,11 +344,11 @@ Payload bytes after the command byte:
| 0 | `mode` | uint8 | 2 = Open Loop, 3 = Show Frame, 4 = Closed Loop |
| 1–2 | `pattern_id` | uint16 LE | 1-based SD pattern index |
| 3–4 | `frame_rate` | int16 LE | Hz — frame-advance rate for Mode 2. Negative values play in reverse. Sign is ignored in Modes 3 and 4. |
| 5 | `gain` | int8 | Mode 4 velocity scale: actual gain = `gain / 10` fps/V (e.g. `−20` → −2.0 fps/V) |
| 6–7 | `init_pos` | uint16 LE | Initial frame index (0-based) |
| 8+ | reserved | — | Legacy G4 fields; accepted and ignored |
| 5–6 | `init_pos` | uint16 LE | Initial frame index (0-based) |
| 7–8 | `gain` | int16 LE | Mode 4 velocity scale: actual gain = `gain / 10` fps/V (e.g. `−20` → −2.0 fps/V) |
| 9–10 | `duration` | uint16 LE | Controller-run trial length, in 10 ms ticks. `0` = no auto-stop; the controller reverts to ALL_OFF on its own when the duration elapses. |

Minimum payload: 8 bytes (offsets 0–7). Full G4-legacy form sends 12 param bytes (`length = 0x0D`).
Frame length is always `0x0C` (12 = cmd + 11 param bytes); all 11 param bytes are required.

**Response (success):** `[0x02, 0x00, 0x08]`

Expand Down