KrustyPlanet/cyberdeck
6
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

document display architecture research and settled design decisions

Browse source 
- eDP direct connection ruled out: undocumented pinouts, voltage mismatch risk,
  community consensus favors controller boards
- MIPI DSI ruled out: 2-lane 15-pin, can't dual-display with HDMI on Linux,
  and the salvaged panel is eDP
- Chosen path: HDMI -> eDP-to-HDMI controller board -> salvaged panel
- Mechanical HDMI A/B switch retained as fallback for external display
This commit is contained in:
BarnacleBoy 2026-05-27 01:12:00 +00:00
parent ce2d3be1e1
commit e53c928e44
2 changed files with 21 additions and 9 deletions
Download patch file Download diff file Expand all files Collapse all files

25
docs/design-decisions.md
View file

@ -50,14 +50,27 @@ IP5389 power bank board (preliminary). All-in-one: charging, BMS, USB-C PD outpu
## Display Connection
The Orange Pi 3B has a **native eDP port** in addition to HDMI. This means:
**Chosen path:** HDMI → eDP-to-HDMI controller board → Innolux N156HGE-EAB panel.
- 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)
The Orange Pi 3B has a native eDP port and a MIPI DSI port, but neither is used. Here's why:
See [sbc-selection.md](sbc-selection.md) for eDP compatibility notes.
### eDP Port — Investigated, Ruled Out
The 30-pin eDP ZIF connector on the OPi3B underside could theoretically drive the salvaged laptop panel directly. In practice, eDP pinouts vary between manufacturers for the power and backlight signals despite VESA's standard for the data lanes. A panel expecting 12V on a pin the SBC sends 3.3V won't light. Send 12V where 3.3V is expected and you get smoke.
Orange Pi does not publish schematic-level documentation for the eDP connector pinout. Tracing it manually (multimeter + RK3566 datasheet) is possible but finicky, and the salvaged panel's exact pinout would need cross-referencing too. The $35 controller board was the right call — it's the proven approach the entire laptop-reuse community uses.
### MIPI DSI Port — Investigated, Ruled Out
The 3B has a 2-lane MIPI DSI port on the back edge (15-pin FFC, Raspberry Pi-compatible form factor). Supported panels include several 5" and 7" Pi-style DSI touchscreens, enabled via the `raspi-7inch-touchscreen` overlay in `/boot/orangepiEnv.txt`. However:
- Enabling DSI **disables HDMI** — the RK3566 can't drive both simultaneously under Linux on the OPi3B (confirmed by community testing and manufacturer)
- The 15.6" salvaged panel is eDP, not DSI — a different interface entirely
- No practical path to use it for the primary display
### Result
The salvaged panel connects via its matched eDP-to-HDMI controller board. The OPi3B's HDMI output drives the controller board. The MIPI DSI and eDP ports remain unused and unpopulated internally.
## Video Output

5
docs/port-layout.md
View file

@ -49,14 +49,13 @@ User-facing. Clean for typing.
|-----------|------------|
| Powered USB hub (10-port) | Decased, wired internally. Feeds all USB-A and USB-C data ports. |
| HDMI A/B switch (mechanical) | Passive toggle. OPi3B HDMI in, two outputs (internal display + starboard panel jack). |
| eDP-to-HDMI controller | Connected to A/B switch output A. Drives internal display — **may be unnecessary if native OPi3B eDP works with panel** |
|| eDP-to-HDMI controller | Connected to A/B switch output A. Drives internal display. |
## Constraints
- OPi3B has **one HDMI output**. The A/B switch selects internal or external — not both simultaneously.
- OPi3B has a **native eDP port** — if the Innolux N156HGE-EAB panel pinout matches, the external controller board is not needed.
- The internal display uses an eDP-to-HDMI controller board (matched to the salvaged panel). The native eDP port on the OPi3B is unused — direct connection was investigated but ruled out due to undocumented pinouts and voltage mismatch risk.
- 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 dual-HDMI SBC.
- USB-C on the OPi3B is **power only** — no DisplayPort alt mode. All video goes through HDMI or native eDP.
- Built-in WiFi 5 + BT 5.0 on the OPi3B — no USB dongles needed for wireless connectivity.
- Two native USB 3.0 ports available for direct connections (keyboard, mouse) without hub contention.