Running the LCD Display Peripheral

emma65-lcd-display is an SDL2 window that renders a display/lcd device’s composited dot-matrix output when running the plain emma65 CLI standalone (the debugger doesn’t need it — its own LCD Display panel renders in-process). Like emma65-display and emma65-led-matrix, it’s spawned by the emulator as a child process and streams data to it over the pipe transport’s stdin, per the LCD Display External Protocol.

Building it requires SDL2 development headers (libsdl2-dev on Debian/Ubuntu, sdl2 on Homebrew), the same as emma65-display and emma65-led-matrix:

cargo build --release -p emma65-lcd-display

Configure a display/lcd device with a pipe: transport pointing at the built binary:

[[devices]]
type = "display/lcd"
address = 0xD000
geometry = "16x2"
transport = "pipe:/path/to/target/release/emma65-lcd-display"

(or the CLI equivalent — see Device configuration examples in Running the Emulator for the general --device syntax).

The window opens as soon as the emulator attaches the transport, showing a blank dot-matrix grid in the device’s configured background color before any writes occur. --pitch sets the initial on-screen dot center-to-center spacing in pixels (default 12); the window remains resizable afterward and letterboxes/scales to fit. Closing the window ends emma65-lcd-display; it also exits cleanly if the emulator process exits or is killed first, since that closes its stdin.

Whether the window can ever show true 5×10 dots is fixed by the device’s configured geometry= — only 8-character-5x10 and 16-character-5x10 have the physical common-line count a real 5×10 glyph needs (see LCD Display). On those two geometries, Function Set’s F bit still switches the active font between 5×8 and 5×10 dots at runtime, and the window resizes on the fly to match, since that changes every subsequent frame’s pixel height — no configuration is needed for the resize itself, it follows automatically from each frame message’s own dimensions. On every other geometry, a program setting F=1 has no visible effect: the font, and so the window’s size, stays fixed at 5×8 for the life of the device.