# Workabout MX barcode scanner — API notes (reverse-engineered)

There is no official SDK documentation for the Workabout MX integral laser scanner.
The Psion SIBO C SDK and I/O Devices Reference predate the MX and describe only the
older *external* barcode modules (wands / wand-emulation), not the integral laser.
These notes are reverse-engineered from device behaviour and from the Workabout MX
ROM `w2mx_v7.20f_eng.bin` (strings), so treat unconfirmed items as such.

## Hardware

- Integral **laser** scanner, Symbol engine. The demo (`DEMMAN.APP`) reports
  `Type: Laser 1223` (some units `1222`).
- It is a **decoded** scanner: it decodes in hardware and lights a green good-read
  LED. It does **not** emit an undecoded (HHLC) signal.
- Trigger: the keyboard **scan key**, which the Window Server reports as key
  code **368**. The key alone does not fire the laser from an arbitrary app; the
  scanner software arms/reads the engine.

## Device driver and ports

`LLDEV` on the device lists a logical driver **`wl2`** (`units=1`). The scanner is
reached through this driver. The demo's "Select Scanner" screen lets you pick both
a **decoder type** and a **port** (device driver + unit letter):

- Port device drivers offered: **`TTY`**, **`WLS`**, **`WL2`**.
  The MX integral laser uses **`WL2`**.
- Units seen in the ROM: **`WL2:A`** and **`WL2:D`**.

Decoder types (from the demo, "chosen from those used in standard Workabout
products"):

| Decoder | Meaning |
| --- | --- |
| `Generic` | External non-configurable reader |
| `Symbol1` | Workabout standard scanner |
| `Datalogic` | Workabout CCD |
| `HP` | Workabout Wand |
| **`Symbol2`** | **Workabout MX scanner (the integral laser)** |

## Opening the device

```c
VOID *h;
INT  err = p_open(&h, "WL2:D", (UINT)-1);
```

Observed results:

| Call | Result | Meaning |
| --- | --- | --- |
| `p_open("WL2:D", -1)` | `0` | **opens** — this is the integral-laser unit |
| `p_open("WL2:A", -1)` | `-9` (`E_GEN_INUSE`) | in use — held by the resident scanner software |
| `p_open("WL2:B" / ":C")` | (untested) | — |

`WL2` has a single unit, so only one process may hold it. `WL2:A` is permanently
`-9` even with the demo closed, indicating a resident holder; `WL2:D` is the unit
an application opens.

## The 11-byte parameter block

The scanner is configured by an **eleven-byte parameter block**. The application
interprets these bytes and converts them into commands for the selected decoder
(so the same block means different wire commands for `Symbol2` vs `HP`, etc.):

| Byte | Parameter |
| --- | --- |
| Param0 | Decode security |
| Param1 | Code type (symbology select) |
| Param2 | Decode options A |
| Param3 | Decode options B |
| Param4 | General parameters |
| Param5 | ITF length 1 |
| Param6 | ITF length 2 |
| Param7 | Preamble |
| Param8 | Postamble byte 1 |
| Param9 | Postamble byte 2 |
| Param10 | General decode options |

The preamble/postamble bytes mean decoded output may carry configurable leading /
trailing characters — parsing code must account for them.

## Access model

Applications do not drive `WL2` byte-by-byte themselves; they use the ROM library
**`SCANNER.DYL`** (used by `SCANAPP.APP` and `DEMMAN.APP`). That library opens the
port, converts the 11-byte block to decoder commands, configures and enables the
engine, and returns decoded scans.

## Paths that do NOT work for the integral laser

Recorded so they are not retried:

- **`bar*.ldd` decoders (`BAREAN`, `BARC39`, …) + `BAR:` device.** These are
  software decoders for the *external* wand modules. Loading `BAREAN.LDD` and
  opening `BAR:A`/`BAR:B` returns `-41` (`E_FILE_DEVICE`, "no interface found in
  slot") — the integral laser is not a `BAR:` expansion interface. `BAR:D`/`BAR:E`
  return `-38` (`E_FILE_NAME`, invalid unit).
- **`TTY:D` serial reads.** Opening `TTY:D` powers the laser (it fires briefly),
  but no decoded bytes ever arrive on the serial channel — not with default
  config, not after `P_FSET` to 9600/8/1, not with `P_OBEY_DSR` cleared, not with
  the intelligent-reader escape commands (`<Esc>-y1J` / `<Esc>-y1K`), not reading
  one byte at a time. The integral laser's decoded data is not on `TTY:D`.

## Open gap (not yet solved)

Opening `WL2:D` succeeds, but the scanner does not start scanning on a bare open —
it requires an **initialisation sequence** (set decoder type, write the 11-byte
parameter block as decoder commands, enable the engine) before a read returns
data. That sequence is the function-code / control protocol of the `WL2` driver
and is implemented in the binary `SCANNER.DYL`; it is **not** present in any ROM
strings or in the SDK.

To close it, one of:
1. The **Workabout MX C SDK** scanner header / `SCANNER.DYL` category definition
   (what `SCANAPP` was built against) — the clean answer.
2. Disassembly of `SCANNER.DYL` / `SCANAPP` from the ROM to extract the `WL2`
   init sequence — large, uncertain effort.

## Error codes seen (from `epocdefs.h`)

| Value | Name | Meaning |
| --- | --- | --- |
| `-9` | `E_GEN_INUSE` | device already open / in use |
| `-32` | `E_FILE_EXIST` | (LDD) already loaded |
| `-38` | `E_FILE_NAME` | invalid device name / unit |
| `-41` | `E_FILE_DEVICE` | device / interface not present |