I think the broad idea isn't to directly, for example, program a floppy disk drive (to boot a PC from BIOS) driver from such a front panel (a gargantuan task), but to gradually bootstrap your way up there.
For example, you could build yourself a makeshift hex keyboard and load a driver for that keyboard onto an ATmega. Good! from that point on, you can enter bytes faster.
Then, you hook a few seg7 together to have some kind of display. Even better!
For example, you could build yourself a makeshift hex keyboard and load a driver for that keyboard onto an ATmega. Good! from that point on, you can enter bytes faster.
Then, you hook a few seg7 together to have some kind of display. Even better!
... and so on, until you can drive that FDD.