Tinkerer and classic expertise fanatic Jim Shortz has constructed a home-brew implementation of traditional Nineteen Seventies reminiscence sport Simon — utilizing a period-appropriate Intel SDK-85 improvement equipment, purchased at a ham meet.
“Just a few weeks in the past, I discovered an Intel SDK-85 Single Board Laptop [SBC] at a ham-fest,” Shortz explains. “I’m a sucker for something with a keypad and seven phase shows. Having had a Heathkit ET-1 disappear in entrance of me, I made positive to behave on this one as rapidly as potential. I did not even know what it was, however I knew I wanted it. It is an Intel 8085 {hardware}/software program improvement equipment from the late Nineteen Seventies. It is aimed on the hobbyist/training market. It sports activities a tremendous guide, beneficiant 36 GPIO [General-Purpose Input/Output] ports and a meager 256 BYTES of RAM.”
The Intel System Improvement Equipment 85 (SDK-85) was launched in 1976 because the successor to the SDK-80, changing the latter’s Intel 8080 processor with an Intel 8085. Along with a more moderen processor working at a better clock pace — 3MHz to 2MHz on the SDK-80 — the SDK-85 supplied an on-board six-digit show, enter keyboard, and assist for 512B of RAM and as much as 4kB of ROM. The gadget served as an illustration of the 8085’s capabilities — which, apparently, contains the flexibility to play a sport of Simon.
“I seemed for an issue house that was properly matched to the SDK-85 and its apparent emphasis on {hardware} integration. The reply turned apparent – recreate the legendary Simon digital sport from 1978,” Shortz explains, referring to Ralph Baer and Howard Morrison’s iconic sound-and-color-matching handheld gizmo, programmed by Lenny Cope.
“That is the place different historical past took over. I think about myself as a lowly hobbyist inventor in my basement. I might afford an SDK-85, however no teletype, and definitely not a ‘actual’ pc. I’d do that with the books, graph paper, pencils, and my trusty HP calculator.”
The {hardware} lives on a wire-wrapped daughterboard, in order to not harm the SDK-85. (📷: Jim Shortz)
What adopted was painstaking reverse-engineering of the hand held, purely from video recordings — with no bodily model of the sport handy — aided by just a few concessions to construct what Shortz admits is a “simplified model of the sport,” together with the lack of selectable problem ranges.
“I made a decision on a indifferent daughter board that may home the 4 push button switches, lights, and speaker,” Shortz explains of his implementation of Simon’s {hardware}, having determined to go away the classic SDK-85 in unique situation. “The daughter board connects to the SDK-85 utilizing a ribbon cable into an IDC header I put in on the port 0/1 connector. The switches I had on-hand have been panel-mount kind, so I drilled by means of the board to mount them — another excuse to maintain these on a daughter board.”
The software program was written by hand on paper, then fastidiously typed in to the demonstrator. (📷: Jim Shortz)
“The board was wire wrapped on a scorching Saturday afternoon and doesn’t signify my finest work,” Shortz provides. “I accomplished the board in its entirety earlier than attending to work on the software program. I wrote the code out on graph paper utilizing a mechanical pencil. The mnemonics began close to the center of the web page. This left room to place the addresses and hex bytes on the left hand aspect of the web page, similar to an assembler program’s itemizing file would use.”
Shortz’ full mission write-up is out there on Hackaday.io, although he readily admits that “the [Intel] 8085 could be a horribly costly selection for a client product with thousands and thousands of items.”