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# Ground Station
Orange Pi Zero 3W supervisor and kiosk display for the custom OpenIPC/WFB ground station.
## Components
The ARM64 artifact intentionally contains two executables:
- `groundstation-linux-arm64` — the long-running root supervisor. It owns the GX12 UART, logging, RC state, video lifecycle, and starts the display process.
- `groundstation-display-linux-arm64` — the unprivileged X11 kiosk renderer. It runs as `orangepi` on `DISPLAY=:0`; the supervisor owns it during normal use.
Current capabilities:
- receives framed GX12 RC channel data at 115200 8N1;
- validates protocol version, frame length and CRC-16;
- logs channel changes instead of every frame;
- starts/stops `fpv-video` from the configured CH6 power/lifecycle control;
- publishes immutable flight OSD snapshots — final RC channels, arm state
derived from the configured arm channel, the adaptive-link contract values
(operator target table, temporary CH6 maxPower ceiling, requested runtime
level, VTX acknowledgment, observed link — pending/unknown until their
producers exist) and decoded-video presence — to a tmpfs state file
without ever blocking the UART, WFB or video paths; unchanged state is
republished as a heartbeat and the file is removed on shutdown;
- starts an independent kiosk display before video, tolerates temporary X11 downtime without restarting the supervisor, and stops deterministically on shutdown;
- keeps the fullscreen fallback/menu canvas below `fpv-video`, showing `Brak połączenia WFB` only while video is absent;
- maps a transparent, input-transparent OSD overlay above `fpv-video` as the flight OSD rendering surface: it never intercepts video input, and it punches its output shape only around the text it draws;
- renders a deliberately minimal Viture OSD on that overlay while decoded video is present — the arm state and one compact adaptive-link line showing the target table, the CH6 maxPower ceiling, the requested runtime level and the applied VTX state, with explicit pending marks until real producers arrive — refreshing on a slower cadence than the video so the pilot stream keeps priority; a stale snapshot (dead UART) stops rendering instead of freezing telemetry over live video.
Future MIPI/touch targets use their own templates rather than sharing one global layout. The flight OSD renders on the existing transparent layer above video, preserving the pilot stream's priority.
## Installation on Orange Pi
Extract the artifact and install **both** files:
```bash
sudo install -m 0755 groundstation-linux-arm64 /usr/local/bin/groundstation
sudo install -m 0755 groundstation-display-linux-arm64 /usr/local/bin/groundstation-display
sudo systemctl restart groundstation
```
Check logs:
```bash
systemctl status groundstation --no-pager
journalctl -u groundstation -b --no-pager -n 80
```
Do not run `groundstation-display` by hand during normal operation. It needs the X11 user/session environment and is managed by the supervisor. For isolated renderer debugging it supports:
```bash
groundstation-display -target x11
```
## Configuration
The service reads `/etc/groundstation/config.yml`. For the verified permanent GX12 connection, use:
```yaml
serial:
path: /dev/ttyS2
```
`/dev/ttyS0` is the Orange Pi boot/debug UART and must not be used for the permanently connected GX12.
The flight OSD is configured alongside:
```yaml
osd:
state_path: /run/groundstation/osd-state.bin
arm_index: 4 # CH5/AUX1, zero-based
armed_threshold: 0 # armed while the arm channel stays above this
vtx_table_gen: 0 # operator-selected VTX table (0 = none selected)
vtx_table_hash: 0
```
CH6 acts only as the temporary operator maxPower ceiling and static
configuration is never applied VTX state. `groundstation-display` reads the
same state file; both sides must agree on
the path (override the renderer's with `groundstation-display -osd-state
<path>` if you change `osd.state_path`). The state file carries only flight
telemetry and never any credentials or keys.
## Runtime dependencies
- X11 session on `:0` owned by `orangepi`; the kiosk waits for X11 and reconnects after display-manager restarts;
- `wmctrl` for the fullscreen/stacking kiosk window states; without it the kiosk windows map as normal windows and the condition is logged;
- `runuser` from util-linux for the unprivileged kiosk launch.