# Design Decisions

## Build Approach

Wooden case with salvaged laptop lid (screen + hinge) as the canopy. Approximate briefcase dimensions, with the display panel setting minimum width and depth.

## Salvage Exclusions

- **Webcam:** Scrapped. Proprietary pinout, not worth reverse engineering.
- **Keyboard/trackpad:** Proprietary connectors, not reusable.
- **RAM:** DDR3L soldered, wrong generation.
- **SSD:** Owner repurposed.
- **WiFi card:** Intel 7265NGW — OPi3B has built-in WiFi+BT, no external card needed.

## Case Orientation & Nomenclature

User sits at the **stern**, facing the **bow**. Hinge axis runs port-to-starboard along the bow edge.

### Base (wooden enclosure)

| Term | Surface | Notes |
|------|---------|-------|
| **Deck** | Top | Keyboard, controls, SBC access |
| **Keel** | Bottom | Sits on table |
| **Bow** | Back edge (spine side) | Power input, heat exhaust, farthest from user |
| **Stern** | Front edge (lip side) | User-facing, keyboard near here |
| **Port** | Left (facing bow) | |
| **Starboard** | Right (facing bow) | |

### Canopy (laptop lid + screen)

| Term | Surface |
|------|---------|
| **Canopy dorsal** | Outside of lid |
| **Canopy ventral** | Screen side |

### Bow Wall Functions

- Power input (5V USB-C for charging)
- Exhaust fans blowing away from user
- Heat management surface

## Carry Handle

Stern edge (lip). Screen is lightweight, hinge is rigid, and a lid latch is planned — so the canopy-open-under-gravity concern is handled. Keeps the bow wall dedicated to power input and exhaust.

## Power System

IP5389 power bank board (preliminary). All-in-one: charging, BMS, USB-C PD output. See [power-system.md](power-system.md) for details.

## Display Connection

The Orange Pi 3B has a **native eDP port** in addition to HDMI. This means:

- The Innolux N156HGE-EAB panel (30-pin eDP) may connect directly — bypassing the external controller board
- Needs verification: the OPi3B's eDP connector type and pinout must match the panel
- If compatible, saves ~$24 and eliminates an external component
- If not, fallback is the eDP-to-HDMI controller board (already ordered)

See [sbc-selection.md](sbc-selection.md) for eDP compatibility notes.

## Video Output

Mechanical HDMI A/B switch (passive, no power). Routes OPi3B's single HDMI to either the internal display (via eDP or eDP-to-HDMI controller) or a panel-mount HDMI jack on the starboard side. DisplayLink doesn't work on ARM — no drivers exist. Dual simultaneous display is not possible on the OPi3B (single HDMI output).

## Input Device

ThinkPad TrackPoint keyboard (specific model TBD based on availability). Chosen for built-in TrackPoint pointer and 15.6" deck space compatibility.

## Carry Handle

Stern edge (lip). Screen is lightweight, hinge is rigid, and a lid latch is planned — so the canopy-open-under-gravity concern is handled. Keeps the bow wall dedicated to power input and exhaust.
