Windows: keyboard scans¶

A scanner with mode: keyboard types each scan into the focused window, like a USB keyboard-wedge scanner. On Windows emupos does this with SendInput. No permission or setup is needed, with the limits below.

Click the POS window during the countdown¶

emupos scan counts down before it types. On macOS and Linux X11 emupos cancels the scan when the terminal still has focus; on Windows it cannot tell, so if the terminal is still focused, the barcode and its Enter are typed into the terminal and run as a command. Click the POS window before the countdown ends, or give yourself more time with --countdown 10.

Run emupos and the POS at the same privilege level¶

Windows discards keystrokes sent to a window that runs with higher privileges than the sender. A POS started with Run as administrator does not receive scans from an emupos that runs as a normal user, and Windows still reports the keystrokes as accepted, so emupos cannot detect these lost scans: emupos scan reports success and nothing arrives. Run both as a normal user, or both as administrator.

If Windows does report refused keystrokes (for example while the lock screen or a UAC prompt is showing), emupos run prints a warning and the scan is not reported as delivered.

Keyboard layouts¶

emupos presses the keys that type each character on a US keyboard, with the virtual-key code and scan code a real keyboard sends, so browsers see KeyboardEvent.code values such as Digit5 and KeyA. The window's active keyboard layout decides which characters come out, exactly as with a real scanner: with the Arabic (101) layout, digits stay ASCII digits but letters become Arabic letters.

emupos scan --unicode (or "unicode": true in the API) types the exact characters whatever the layout. These characters carry no physical key: a browser reports an empty code and, on key up, key Unidentified. An application that reads key positions or key codes does not see the keys a scanner would press; use --unicode only for applications that read the typed text.

Serial mode instead¶

A serial scanner writes each scan to a COM port that the POS opens, with no keyboard involved; see windows-serial.md.