# Dasung Paperlike display

FDS includes `dasungd` for the configured Dasung Paperlike 13K grayscale monitor.
The controller starts during early boot and remains supervised in the base system,
including console-only use. No GUI or ENVIRONMENT cartridge is required.

The supplied profile uses the dedicated monitor's EDID and USB companion identity,
with raw mode 1 and contrast 4 as startup defaults. It is specific to that monitor;
do not use its identity as a blanket match for other CH340 USB devices.

## Inspect the controller

The controller's socket is restricted to root. From a root maintenance console
on FDS:

```sh
dasungd status
dasungd query
```

`status` reports whether the monitor is connected and responsive, the age of its
last reply and cached parameters. `query` requests current values. To refresh
the display or adjust contrast:

```sh
dasungd refresh
dasungd set contrast 4
dasungd set mode 1 --save
dasungd forget mode
```

A successful set means the command was sent; use query/status to read back the
result. The grayscale model uses raw numeric modes. Saved overrides in
`/run/dasungd/settings.json` survive a daemon restart during the same boot, but
not power loss. Image configuration defaults are in `/etc/dasungd.toml`.

## Diagnose a connection problem

Inspect `/run/log/dasungd/current` and the reported status. Discovery requires
the configured DRM EDID and matching USB companion topology. An ambiguous match
is rejected. Set `usb_path` only after identifying the intended device topology.

FDS uses the daemon for USB control. Its configuration disables the original
workstation-specific display hotplug procedure. Video mode and cabling are part
of the machine's boot/display configuration. The detailed protocol, build
rationale and physical display procedures are in the
[developer reference](developer/dasung.md).