parking_solution/wiki/entities/dingtian-relay.md

---
type: entity
tags: [parking, hardware, access-control, relay]
sources: []
updated: 2026-06-14
---

# Dingtian Relay Controller

A network **relay + input** board (the unit on hand is the **4-channel** variant: 4 relays + 4
inputs). Chosen to drive the entry/exit lane because — unlike the [[uhppote-controller]] — its
**inputs are independent of its relays**, which solves the [[access-controller-button-flow]]
blocker (a button on an input does not auto-open a relay; the host decides).

SDK: `dingtian/4ch/sdk_v2_0_0/` (programming manual, examples). MIT-compatible use; no vendor
runtime needed.

## ⚠️ The one gotcha: `input_link_relay`

By **default the device links each input to auto-fire its matching relay** (`input_link_relay: 1`,
`on_action_on: [[0],[1],…]` in the config) — i.e. the *same* auto-open problem as the UHPPOTE.
The difference: **it is configurable.** Set `input_link_relay: 0` (or clear the action mappings)
so an input only *reports* and the host commands the relay. **This config step is mandatory** for
the ticket-first entry flow. See [[autonomous-direction]].

## Protocol (Dingtian string — what we use)

Transport options: UDP/TCP string, UDP binary, HTTP CGI, Modbus, MQTT. We use **HTTP + UDP** —
see [[dingtian-vs-mqtt]].

- **Relay control — UDP *binary*, port 60000 (authenticated):** the driver's `pulseOpen` sends a
  binary "write relay with jogging" frame carrying the `relay_pw` (the only relay option with a
  password). Frame (verified on hardware):
  `FF AA <session> 03 <pwLo> <pwHi> <relayByte> <jogLo> <jogHi>` — relayByte bit0=on, bits1-7=
  channel-1; jog is 100 ms units, LSB-first; password 16-bit LSB-first (0 = none). The relay jogs
  ON then auto-releases, so we never time a close ([[barrier-not-a-door]]). *(The simpler string
  protocol — `1`+ch on, `2`+ch off, `11*` jog — works too but has no auth; we use it only for the
  read-only status query.)*
- **Status / inputs — send `00`** → `「relays」:「inputs」:「count」`, e.g. **`0000:1111:4`** (4ch:
  relays off, inputs high). `0` = OFF/Low, `1` = ON/High. Poll-based.
- **Input push — `input_link_url`:** device **HTTP POSTs to a host URL on input change** — the
  push path for button events without a broker.
- **Discovery:** UDP multicast `224.0.2.11:60000`, send `\x05\xAA` (devices reply). Defaults:
  IP `192.168.1.100`, UDP `60000` (binary) / `60001` (string).
- Binary protocol (port 60000) adds optional **password** + multicast; bitmask relay/input maps.

## Driver & config API

The `dingtian` driver ([[device-registry]]) implements three capabilities:
`AccessControlDevice` (relay pulse/latch over UDP), `InputDevice` (read inputs + poll-based
press/release events ~50 ms), and `PreconditionDevice` (below). Config fields include a separate
**`httpPort`** — the device's web/config API is on a configurable HTTP port (default **80**),
distinct from the UDP control port 60001.

### Precondition: input_link_relay must be OFF

The driver reads the device's JSON config (`GET /api/v2/config.cgi`) and **checks
`input_link_relay`**; if enabled it reports a fixable issue, and `fixPreconditions()` writes the
correction (`POST /api/v2/config_set.cgi`) — setting the flag to 0 and clearing `on_action_on`,
preserving everything else (network, etc.). This is the generic [[device-registry|precondition]]
capability: the app doesn't own full device config (that's the vendor web UI), only the few
settings our flow depends on.

> **Write gotcha (cost real debugging):** the GET config payload **omits** a `"command"` field, but
> the set endpoint **requires `"command":"setconfig"`** injected right after `"status"`. Without it
> the POST returns/looks like success but silently does nothing (and the device may reset). With it,
> POST returns `{"status":0}` and the change sticks. JSON node order must be preserved.

## Input push (no polling) — the chosen architecture

The device **pushes** button events to the backend; the backend decides. **No polling.** The
driver's `configureInputPush()` writes the device's `input_link_url` config to point each input at
the backend: input N HTTP-GETs `…/api/devices/dingtian/<deviceId>/input/<N>/on` (and `/off`) on
press/release. The backend ([[fastify]] route `routes/devices.ts`) translates each push into an
internal device event ([[device-input-flow]]); the entry flow then prints a ticket and commands
the relay via UDP. See [[device-input-flow]] for the full path + trust model.

> The input-poll path in the driver (`onInput`) remains as a dev/fallback aid, but **push is the
> real path** — lower latency, and it can be authenticated (the device supports Basic/Digest +
> HTTPS on the push), unlike the open UDP control direction.

## Hardening (`harden()`) — and why HTTP auth is not a boundary here

On assign the driver runs `harden()` (the [[device-registry|HardenableDevice]] capability):
1. **`relay_pw`** — set a random relay password so binary relay commands (UDP 60000) need it.
2. **Disable unused channels** — set `p:255` on rs485/can/tcp×2/mqtt; keep only UDP1 binary
   (relay control) + UDP2 string (status read).
3. **Rotate the `admin`/`admin` web login** — `GET /userset.cgi?<old_u>&<old_p>&<new_u>&<new_p>&`
   (response `&0&…&` = success, verified on hardware). The new password is stored back in
   config (`webUser`/`webPassword`) so a re-run can rotate again (the device checks the *old*
   creds). This step is **best-effort** — a failure logs and does not fail the assign.

> ⚠️ **The device CGI API is UNAUTHENTICATED.** Verified on hardware: `GET /api/v2/config.cgi`,
> `/`, and even `/userset.cgi` all return **200 with no credentials**. The `admin`/`admin` login
> gates only the interactive **browser UI** — the CGI control plane (read/write full config, fire
> relays, change the password) bypasses it entirely. The `http` config block has **no** setting to
> require Basic/Digest on inbound requests; the only inbound gate is `session_en`, which **bricks
> the config-read API on this firmware** (the factory-reset incident — *do not enable it*). So
> **rotating the login is cosmetic** (stops a casual browser reaching settings); it is **not** a
> boundary. On this flat, no-VLAN network the device control plane is effectively open — the
> **signed event log is the real anti-fraud guarantee**. See [[device-input-flow]].

> ⚠️ **`session_en` must stay OFF.** Enabling the HTTP CGI session check makes the config-read API
> drop connections (ECONNRESET), locking out the API the driver depends on — recoverable only by
> factory reset. `harden()` deliberately never touches it.

## Status — VERIFIED on hardware (DT-R004, sw V3.1.5461A, 10.0.10.172)

- ✅ status read (`0000:1111:4`), relay pulse, input press/release events (active-LOW, idle HIGH).
- ✅ **`input_link_relay` disabled via the driver** → pressing an input reports the event and
  **fires NO relay** (`0000` after presses). The [[access-controller-button-flow]] blocker is
  **solved**.
- ✅ **Input HTTP-push end to end** — configured the device via `configureInputPush()`, then real
  button presses (all 4 inputs) **pushed to the backend** (`/input/N/on` + `/off` per press,
  source = the device IP). No polling. Host-in-the-loop entry (`button → backend → ticket →
  backend opens relay`) is real.
- ✅ **Web-login rotation** — `userset.cgi` rotates `admin`/`admin` (response `&0&/&`; wrong old
  password → `&2&/&`). Confirmed the device validates the old creds. **Also confirmed the CGI API
  needs NO auth** (config dump + `userset.cgi` return 200 unauthenticated) → rotation is cosmetic.
- ⬜ Next: wire the actual entry flow (input event → signed event + print ticket → `pulseOpen`).