This project is SBC (Single Board Computer) with VGA+PS/2+SD card - think about something comparable to Sinclair ZX81, but based on Atmega2560 (Arduino Mega)

• 10x10 cm size - cheap PCB, based on Arduino Mega Pro - cheap source base parts, SysBus for connection to other boards
• VGA monitor allows for 40x25 character screen where each line can have 4bit foreground and 4bit background colors. (later 320x200 graphic with fore/background colos for each whole line). It can use also projectors or any conversion cabel (I hope, I tested one and it worked)
• PS/2 keyboards are still manufactured and use even with new motherboards, so it is easy and cheap get one.
• This computer use FORTH for it operating system. It allows for interactive developement of functions (aka "words") and programs and allow for GPIO pins manipulation (and more) so Blink and similar LED+buttons can be made immediately on whim without compiling and uploading.
• this also helps with testing any components connecterd to the SBC
• SD card allows for simple data and programs storage which is compatible with common PC/NB (usal FAT SD card).
• external RAM expands atmega2560 8kB RAM to full 64kB RAM which allows for uploading large programs dynamically
• internal FLASH is 256kB which allows for large buildin libraries

FORTH allows for programs both in FLASH (compiled in) and in RAM (typed in or uploaded from SD at runtime). It is based on stack, all functions get argument(s) from stack and return result(s) to stack so it is easy to test each single function interactively and be sure it works. This lead to faster developement.

It is also easy to add new "words" to the FORTH, be it written in C/C++ or composed in FORTHlike style, so everybody can improve this computer for his/her own needs.

(I was working on 8bit computer, and needed graphic card and keyboard interface for input/output, so I placed this module on single board for developement and it turns out, that it is interesting on its own as SBC. The SysBus connector on its back if for 8bit comp, for SBC it can be ignored (maybe hardwired to add another 128lB of slow RAM))

Project is hosted on GitHub, for this HW version use branch MHF-001

https://github.com/githubgilhad/MegaHomeFORTH/tree/MHF-001