# pricegod label daemon (macOS)

One service on `localhost:7790` that drives **both** printers over raw USB:

| device | role | how |
|---|---|---|
| **Urovo D812R+** | prints TSPL labels, programs UHF chips | raw TSPL, `urovo.py` |
| **Dymo LabelWriter 450** | prints the paper label | raw raster, `dymo.py` — **no CUPS driver, no print dialog** |
| Chafon H-102 | reads tags off the shelf | *not this service* — see “Chafon” below |

It is the Mac counterpart to the Windows `daemon.cs` and keeps the same HTTP contract,
so it stays a drop-in for the PriceGod extension's `daemon.js` client.

### Two things worth knowing up front

**`UHF WRITE` commits immediately — it does not wait for `PRINT`.** `daemon.cs` assumed the
encode only fired together with `printlabel`. It doesn't. That means the Urovo can program
a chip while printing nothing, which is what makes the split flow (Urovo encodes, Dymo
prints) possible, and it lets the daemon read the chip back to *verify* an encode before
spending a label on it.

**The Chafon works over serial on macOS.** ASSESSMENT.md §4 found the gun was HID-keyboard
only on Windows. On the Mac it enumerates a CH340 bridge at `/dev/cu.usbserial-*` and the
existing Node `rfid-daemon` speaks its protocol fine, so that dead end is Windows-specific.

**No vendor SDK required.** `ASSESSMENT.md` §7 assumed the RFID encode was locked inside
the Windows-only `GTSPL_SDK.dll` and would need a USB sniff or the Java jar to recover.
It doesn't: the DLL is a managed .NET assembly, and its IL shows every RFID call is a
one-line `String.Concat` → ASCII → `WritePrinter`. The wire format below was recovered
from `ldstr` order + argument order and independently confirmed by a second decompile.

```
UHF WRITE <fmt>,<start>,<len>,<bank>,"<data>"     # the RFID encode
UHF READ  <fmt>,<start>,<len>,<bank>
UHF QUERY <fmt>,<pcStatus>,<crcStatus>
UHF GEN2 EPC|TID|USER|ACCESS|KILL <action>,"<pw>"
SET RFID  <tagType>,<rw_pos>,<void_printout>,<tryEncode>,<errHandle>,<speed>,<retry>
&DEFAULT,i        # rfidSetupDefault      &CALIBRATE,A,R    # RFIDAutoCalibration
PRINT <set>, <copy>                                # note the space after the comma
```

All plain ASCII, one command per line, CRLF-terminated. `writeUHF("H",2,12,"E",epc)`
emits exactly `UHF WRITE H,2,12,E,"<24 hex chars>"`.

## Setup

```bash
./setup.sh          # brew install libusb + venv with pyusb/pillow/segno
```

Then double-click **`start-daemon.command`** (leave it open while you work).

## Files

| File | What |
|---|---|
| `urovo.py` | Urovo USB transport + the full GTSPL command set, status decoding, fault recovery, SKU↔EPC packing. Runs standalone as a connection test. |
| `dymo.py` | Dymo LabelWriter 450 raster driver over raw USB. Runs standalone to report status/revision. |
| `label.py` | Renders the label to a 1-bit bitmap with PIL, resolution-aware (203 dpi Urovo / 300 dpi Dymo). Run standalone to dump previews to `/tmp`. |
| `daemon.py` | The `:7790` HTTP service. |

## Routes

| method | path | body / query | returns |
|---|---|---|---|
| GET | `/devices` | — | **status of Urovo, Dymo and Chafon in one call** |
| GET | `/status` | — | Urovo only: `{ok,ready,status,statusText,printer}` |
| POST | `/tag-and-print` | label fields + `{sku,releaseId}` | **Mode A in one call: Urovo programs the chip, Dymo prints the paper** |
| POST | `/encode` | `{sku,releaseId}` | programs the chip at the antenna and reads it back. **Prints nothing, costs no label** |
| POST | `/print-paper` | label fields + `size?`, `density?` | prints on the Dymo |
| POST | `/print-encode` | `{sku,releaseId,artist?,title?,genre?,style?,info?,price?,condition?,size?,w?,h?,gap?}` | Urovo one-pass print **and** encode (needs RFID stock) |
| POST | `/write-tag` | alias of `/print-encode` | same |
| POST | `/print-test` | same body — Urovo prints only, no RFID (safe on chipless stock) | same |
| GET | `/read-tag` | — | `{ok,epc,sku,releaseId,recognized}` |
| GET | `/read-raw` | — | every memory bank |
| GET | `/preview?size=large&artist=…` | — | **PNG of the label, printing nothing** |
| GET | `/profiles` | — | the media profiles below |
| POST | `/calibrate` / `/recover` | — | RFID auto-calibration / clear a latched fault |

Use `/preview` while tuning a layout — it costs no labels.

## Which flow to use

- **Mode A — separate (today, existing stock).** `POST /tag-and-print`. The Urovo programs
  the chip on an RFID label; the Dymo prints the paper; you stick the paper over the chip.
  The encode is verified *before* the paper prints, so a failed write wastes nothing.
- **Mode B — one pass (the goal).** `POST /print-encode` on direct-thermal RFID paper
  (ASSESSMENT.md §5). One label, printed and encoded together.

## The Dymo, without a driver

The LabelWriter 450 (`0922:0020`) is a bidirectional USB printer-class device, so the
daemon writes its raster protocol straight to the bulk endpoint. **No DYMO driver, no CUPS
queue, no open-window/cmd-P/cmd-W.** Command set is from DYMO's own *LabelWriter 450 Series
Technical Reference Manual*; `dymo.py` documents each command it uses.

Note the two printers differ in orientation: the Urovo's 24 mm web feeds narrow-edge-first
so the design is rotated 90°, while the Dymo's 57 mm head is wider than the label so the
same design feeds landscape and must **not** be rotated. `label.render(..., rotate=)`
handles this, and the resolution difference (203 vs 300 dpi) comes from `profile(dpmm=)`.

## Chafon, and the `:7790` collision

⚠️ The existing Node daemon at `~/Documents/pliceclogs/rfid-daemon` **also listens on
:7790**. Both cannot run at once. That daemon owns the Chafon serial protocol
(`CF [ADDR] [CMD] [LEN] [DATA] [CRC16]` @115200) plus the postal-scale and inventory
routes, none of which this service implements — so it is *not* a full replacement.

Pick one of: run this on `--port 7791`; keep the Chafon daemon for the gun and run this
one elsewhere; or fold the Chafon protocol in here. Unresolved — decide before wiring the
extension.

## Media profiles

Both shop stocks sit on a **24 mm web** and feed long-edge-first, so the landscape design
is rotated 90° onto the media. Names match the extension's size dropdown.

| profile | label face | pitch | notes |
|---|---|---|---|
| `small` | 51 × 19 mm | 51 mm | older stock; the rest of the 24 mm web is blank filler, design is centred across it |
| `large` | 55 × 24 mm | 55 mm | current stock (default) |
| `xlarge` | 64 × 34 mm | 64 mm | untested |

Each inherits `margin_mm` (default 1.5), a safe-area inset held back from every edge —
without it the design runs edge-to-edge and the least registration drift clips it.
Override per request with `size`, or `w`/`h`/`gap` directly.

## Gotchas confirmed on macOS

1. **`0x08` "out of ribbon" is a latch.** `SET RIBBON OFF` alone will *not* clear it — it
   also needs a `FORMFEED` (costs one blank label). `recover()` / `POST /recover` does this.
2. **The status byte lies for 1–3 s after a print** (transient `0x20`/`0x31`/`0x45`).
   Never judge a print by the immediate post-print byte; poll until it settles to `0x00`.
3. **`VOID0` stamps on chipless stock.** If RFID encoding is armed, every label without a
   chip gets voided. `SET RFID OFF` stops it; `/print-test` is the safe route on plain
   thermal. Note `&DEFAULT,i` appears to *arm* RFID, so don't send it casually.
4. **Bidirectional USB is required.** `UHF READ`/`QUERY` reply with raw bytes on the
   bulk-IN endpoint, so CUPS `lp -o raw` is not sufficient — hence libusb.
5. **After changing stock**, calibrate on the printer itself: hold **FEED** while powering
   on and wait for **5 beeps**.

## SKU ↔ EPC scheme (⚠ still unverified)

96-bit EPC = **6 bytes** 14-digit timestamp SKU + **4 bytes** release_id + **2 bytes**
`0xEC01` marker — ported byte-for-byte from `daemon.cs`. Confirm against an existing
Chafon-written tag before trusting it; if it differs, change **only** `epc_encode` /
`epc_decode` in `urovo.py`.