add port layout and video output decisions

- Mechanical HDMI A/B switch for internal/external display toggle
- DisplayLink rejected: no ARM drivers exist
- 10-port layout split across 4 surfaces
- Port side: 4x USB-A, 1x USB-C data, 1x USB-C PD out
- Starboard: Ethernet, HDMI out, 3.5mm audio
- Bow: USB-C power input + fan exhaust
- Stern: handle, SD reader, Kensington lock
- Updated BOM with HDMI switch, panel-mount cables, SD reader
- Cost estimate now ~58

docs/design-decisions.md

@@ -40,10 +40,18 @@ User sits at the **stern**, facing the **bow**. Hinge axis runs port-to-starboar
 - 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.
 
+## Video Output
+
+Mechanical HDMI A/B switch (passive, no power). Routes OPi5's single HDMI to either the internal 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 base OPi5.
+
 ## Input Device
 
 ThinkPad TrackPoint keyboard (specific model TBD based on availability). Chosen for built-in TrackPoint pointer and 15.6" deck space compatibility.

docs/parts-list.md

@@ -24,7 +24,7 @@
 
 | Item | Specification | Source | Est. Cost | Status |
 |------|--------------|--------|-----------|--------|
-| USB hub | Powered 7-port USB 3.0 | Amazon | $15-25 | To purchase |
+| USB hub | Powered 10-port USB 3.0 | Amazon | $20-25 | To purchase |
 | USB enclosure | SATA 2.5" USB 3.0 | Amazon | $10-15 | To purchase |
 | (or) USB flash | 128GB USB 3.0 | Amazon | $15-25 | Alternative |
 
@@ -43,7 +43,13 @@
 |------|--------------|--------|-----------|--------|
 | WiFi dongle | USB, Linux-compatible | Amazon | $10-15 | To purchase |
 
-### Optional
+### Video & Case Integration
+
+| Item | Specification | Source | Est. Cost | Status |
+|------|--------------|--------|-----------|--------|
+| HDMI A/B switch | Mechanical, passive, bi-directional | Amazon | $8-12 | To purchase |
+| Panel-mount cables | USB-A, USB-C, HDMI, Ethernet, audio | Amazon | $15-25 | To purchase |
+| Panel-mount SD reader | USB 3.0 | Amazon | $5-8 | To purchase |
 
 | Item | Purpose |Source | Est. Cost |
 |------|---------|--------|-----------|
@@ -62,20 +68,21 @@
 | SBC | $104 |
 | Display controller | $24 |
 | MicroSD | $12 |
-| USB hub | $20 |
+| USB hub | $22 |
 | USB enclosure | $12 |
-| Power system (board+cells+fuse+charger) | $32-56 |
+| Power system (board+cells+fuse+charger) | $44 |
 | WiFi dongle | $12 |
-| **Subtotal** | **$206-230** |
+| HDMI switch | $10 |
+| Panel-mount cables + SD reader | $23 |
+| **Subtotal** | **$258** |
 
 ### With Optional Items
 
 | Category | Cost |
 |----------|------|
-| Base build | $206-230 |
+| Base build | $258 |
 | Heatsink/cooling | $10 |
-| Panel-mount cables | $15 |
-| **Total** | **$231-255** |
+| **Total** | **$268** |
 
 ### Future Additions
 
@@ -101,6 +108,10 @@
 - IP5389 power board + 18650 cells
 - 5A fuse + holder
 - USB-C PD wall charger (45W+)
+- Powered 10-port USB 3.0 hub
+- Mechanical HDMI A/B switch
+- Panel-mount cables (USB-A, USB-C, HDMI, Ethernet, audio)
+- Panel-mount SD card reader
 - WiFi dongle
 
 ---

docs/port-layout.md

@@ -0,0 +1,59 @@
+# Port Layout
+
+## Overview
+
+10 accessible ports + SD reader + Kensington lock, split across four case surfaces.
+
+## Port Side (Left, Facing Bow)
+
+Data connections. "Plug and unplug frequently" zone.
+
+| Port | Count | Source | Notes |
+|------|-------|--------|-------|
+| USB-A 3.0 | 4 | Powered hub | Flash drives, peripherals, keyboard, hardware |
+| USB-C (data) | 1 | Powered hub | Modern peripherals, data transfer |
+| USB-C PD out | 1 | IP5389 board | Phone charging, 5V/??W |
+
+## Starboard Side (Right, Facing Bow)
+
+Networking + AV. "Plug in and leave" zone.
+
+| Port | Count | Source | Notes |
+|------|-------|--------|-------|
+| Ethernet RJ45 | 1 | OPi5 native | Gigabit, panel-mount extension |
+| HDMI out | 1 | HDMI A/B switch | External display, switched from internal screen |
+| 3.5mm audio out | 1 | OPi5 native | Headphones, speakers, line-out |
+
+## Bow Wall (Back Edge, Spine Side)
+
+Power and cooling. No data ports.
+
+| Feature | Notes |
+|---------|-------|
+| USB-C power input | For IP5389 board charging |
+| Fan exhaust grilles | Blowing away from user |
+
+## Stern Edge (Front Edge, Lip)
+
+User-facing. Clean for typing.
+
+| Feature | Notes |
+|---------|-------|
+| Carry handle | Stern-mounted per design decision |
+| SD card reader | Panel-mount, for camera cards / quick imaging |
+| Kensington lock slot | Physical security |
+
+## Internal Components
+
+| Component | Connection |
+|-----------|------------|
+| Powered USB hub (10-port) | Decased, wired internally. Feeds all USB-A and USB-C data ports. |
+| HDMI A/B switch (mechanical) | Passive toggle. OPi5 HDMI in, two outputs (internal controller + starboard panel jack). |
+| eDP-to-HDMI controller | Connected to A/B switch output A. Drives internal display. |
+
+## Constraints
+
+- OPi5 has **one HDMI output**. The A/B switch selects internal or external — not both simultaneously.
+- DisplayLink USB graphics adapters **do not work on ARM Linux** (no drivers). Not a viable path for dual display.
+- Dual simultaneous display would require a different SBC (OPi5 Plus has 2× HDMI) or x86 board.
+- USB-C on the OPi5 is power-only in this build (consumed by IP5389 board). All USB data goes through the powered hub.