It’s very probably that any of you who’ve constructed a keyboard have executed so utilizing a key matrix related to a microcontroller or, when you’re old skool, a microprocessor. The CPU can scan the keyboard matrix with ease and relay no matter is typed both to the software program it’s working or to a bunch pc. Nevertheless, there was a time when out there processors weren’t thought of highly effective sufficient to do all this and likewise carry out a helpful job, so the keyboard would have its personal decoder chip to output ASCII over a parallel interface. It’s an period [John Calhoun] goes again to with Adam74a small ASCII terminal that receives its enter from this 7-bit parallel port.
Rather than a forest of TTL chips that will have adorned the originals, this engaging curved laser-cut acrylic housing homes an LCD show and a Teensy microcontroller board. There’s a stage change for the traditional 5 volt logic and naturally a small buzzer for the fundamental BEL character. Today, when the parallel interface is comparatively uncommon, it describes the reinvention of alternate floor traces in a ribbon cable to reduce crosstalk. If you wish to strive your individual, every little thing might be discovered on GitHub.
All in all, it’s a enjoyable solution to reinvent an outdated concept.