julian
bf37106c5c
The reader on hand is a GEE-QR-ER80 QR/DataMatrix/1D barcode access reader (not an EM4100 prox-card reader as first guessed). Interfaces: Wiegand 26/34, RS-232, RS-485, USB, TCP/IP; 4-15 VDC; Linux-supported. Variant on hand: -Q-W (QR scanner, Wiegand/RS-232/485). This is the QR-ticket scanner the design already needed: a host-side reader whose scans become read-bus events consumed by the (already-built) exit flow and QR-permit path. Prefer RS-232/485 over Wiegand (Wiegand can't carry a variable-length QR string; autonomy is moot with the no-ACL Dingtian). New source + entity pages; updated ticket-encoding, entry-exit-readers, index. Open (blocks the adapter): the RS-232/485 frame + baud (ASCII CR/LF expected).
58 lines
3.1 KiB
Markdown
58 lines
3.1 KiB
Markdown
---
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type: concept
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tags: [parking, domain, business, devices, entry-flow]
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sources: []
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updated: 2026-06-15
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status: open
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---
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# Ticket Encoding & Scanning
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How a transient [[parking-session]]'s **ticket id** is printed, carried by the customer, and read
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back at the pay station and exit. This is the **physical backbone of the transient flow** — the
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thing that links entry → pay → exit when there's no plate.
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## The ticket id is the session key
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At entry the system mints a `vehicle_entry` event with a **ticket id** (`identity`) and prints a
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ticket the customer keeps. That same id is read back later to find the session. Properties the id
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must have:
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- **Opaque + unguessable** — a random id (not a sequential count an attacker could iterate to claim
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someone else's cheaper session). Sequential **physical** stock numbering is a separate
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reconciliation aid ([[reconciliation]] pre-numbered stock), not the scan key.
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- **Single logical session** — scanning it at the pay station finds the open session; after payment
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it's the proof-of-paid the exit checks.
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## Encoding: QR (preferred) — printed by the booth dispenser
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- The [[rongta-printer]] prints the ticket id as a **2D barcode (QR)** plus human-readable text and
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entry time. QR over 1D barcode: denser, tolerant of crumpling/partial reads, easy for a cheap
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camera/imager to read.
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- **Scan points** (both host-side reads — [[entry-exit-readers]]):
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- **Pay station** — customer scans the ticket → host finds the session → shows fee → takes
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payment ([[tariff]], pay-on-foot) → appends `payment`.
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- **Exit lane** — customer scans the (now paid) ticket → host validates paid + within
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`gracePeriodExit` → `vehicle_exit` → `pulseOpen`.
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- The **scanner is a device behind an adapter** ([[device-adapter-pattern]]): a new `ReaderDevice`
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kind (QR/barcode imager) — likely the same `IdentitySource = "ticket"` / `"qr"` path. Keeps the
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app device-agnostic; hardware model is procurement ([[bom]], [[open-questions]]).
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- **On hand:** the **[[gee-qr-er80]]** QR access reader (`-Q-W`: QR scanner, Wiegand/RS-232/RS-485,
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Linux-supported) — the concrete scanner for this path. A serial `ReaderDevice` adapter feeds the
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`read` bus; pending the reader's RS-232 frame/baud (see [[gee-qr-er80]] open questions).
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## Ticketless alternative (plate as the ticket)
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Where the [[opencv-anpr-service|vision service]]/LPR captures the plate, the **plate can be the
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session key** instead of a printed ticket — drive in, plate read, drive to pay station and enter
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plate (or it's looked up), pay, exit by plate. No paper. The two can coexist per lane
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([[entry-exit-readers]] "both share a relay"); a printed QR ticket is the fallback when a plate
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isn't captured or is low-confidence (recognition is advisory — [[opencv-anpr-service]]).
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## Open
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- QR symbology/error-correction level + what else prints (site name, tariff summary, help number).
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- Scanner hardware (imager model; same unit at pay station and exit?).
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- Lost/damaged ticket → the lost-ticket path ([[parking-session]], [[tariff]] admin-arbitrary
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amount).
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