---
type: concept
tags: [parking, architecture, devices, configurable]
sources: [parking-system-architecture]
updated: 2026-06-15
---

# Device Registry (selectable drivers)

How the system goes from "device-agnostic in principle" ([[device-adapter-pattern]]) to
"**admin picks the device at setup**" in practice. A **registry** holds a catalog of supported
**drivers**, grouped by category; the [[first-run-setup]] UI reads it so an
operator can choose a device per lane and fill in its connection config.

> Implementation-derived (from `packages/devices`), not the source doc.

## The four categories

| Category | Examples (drivers) | Interface |
| --- | --- | --- |
| **access** | ZKTeco, ESP32 relay (also UHPPOTE) | `AccessControlDevice` — intent-only relay ([[barrier-not-a-door]]) |
| **reader** | Wiegand-into-controller, TCP/IP reader | `ReaderDevice` — RF/optical; two paths ([[entry-exit-readers]]) |
| **camera** | Hikvision, Dahua | `CameraDevice` — entry/exit snapshot-on-event |
| **printer** | (ticket dispenser / booth printer) | `PrinterDevice` |

## How a driver is described

Each driver declares: a stable `id`, its `category`, a human `label`/`description`, the
`transports` it uses (`tcp-ip`, `wiegand`, …), a list of **`configFields`** (host, port,
credentials, selects — what the setup UI renders), and a `create(config)` **factory** that
validates config and returns a live adapter. Adding hardware support = registering one more
driver; **no business-logic change** — this is the [[device-adapter-pattern]] made selectable.

## Why a registry (not hard-coded wiring)

- The admin chooses between **multiple devices per category** at install time, per lane
  (mirrors the "mixable per lane" principle — see [[trust-boundary]], [[entry-exit-readers]]).
- Config is **validated against the driver's declared fields** before persisting.
- Selections persist in the `lane_devices` table and drive runtime adapter construction.
- Drivers may optionally implement **[[device-discovery]]** (`discover()`), so the admin can scan
  the LAN instead of typing connection details — no current driver uses it (the UHPPOTE did,
  before removal; the [[dingtian-relay]] uses a fixed IP).

Cameras are modelled as **snapshot-on-event**: the host requests an image at entry/exit; it's
stored and referenced from the signed event as an **independent record** — a fraud-control input
to the [[append-only-event-chain]] (cf. [[lpr-camera]] as the recognition-based identity source).