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+# inventory
+
+A demo inventory application for the Psion Workabout MX: scan UPC barcodes, and
+(Phase 2) keep stock counts in a database file, adding stock or consuming it by
+scanning.
+
+Written in PLIB C, built with the TopSpeed compiler (`tsc /m scan`).
+
+## Phases
+
+- **Phase 1 (this commit): scan and validate.** Reads barcodes from the scanner
+  and prints each one, flagging whether it is a valid UPC-A.
+  Modules: `upc` (validation), `bcode` (scanner input), `scan` (the demo).
+- **Phase 2 (next): inventory database.** A DBF file keyed on UPC holding a
+  quantity and a name. Scan to add stock (increment, or create on first sight),
+  scan to consume by a quantity unit. Built on the SIBO `Dbf*` API.
+
+## Build
+
+```
+tsc /m scan
+```
+
+Produces `scan.img`. `scan.pr` compiles `upc.c`, `bcode.c` and `scan.c` and
+links them.
+
+## How the scanner is read
+
+On the Workabout the barcode module decodes the label in hardware and sends the
+result as an RS232 stream, so there is no special barcode driver call: the app
+opens the serial port and reads it. The scanner is on the top internal slot,
+which is port **D**, so the device is `TTY:D` (`bcode.c`).
+
+The scan loop is asynchronous: it waits on the scanner and the keyboard at the
+same time, so a scan is processed immediately and Esc quits at any point.
+
+## Things to confirm on the device
+
+Because this cannot be compiled or run off-device, these points are written to
+the SDK docs but may need adjusting once you build and test:
+
+- **Serial line settings.** `bcodeOpen` opens `TTY:D` with the default mode. If
+  the scanner needs a specific baud/parity/framing, configure the channel with
+  `p_iow(chan, P_FSET, &config)` (E_CONFIG, `p_config.h`) after opening.
+- **Terminator.** `BCODE_TERM` in `bcode.h` is set to CR (`0x0D`), the common
+  case. Change it if your scanner suffixes LF or something else.
+- **Esc key code.** `KEY_ESC` in `scan.c` is `27`; adjust if the console
+  delivers a different code.
+- **`CON:` async read.** Phase 1 reads single keystrokes asynchronously from
+  `CON:`; if that behaves differently on your unit, the keyboard handling in
+  `scan.c` is where to look.