ADAM’74, a retro display for 8-bit computers #VintageComputers #Retrocomputers

The Adam74 is a little project that tries to act as a little terminal that a hobbyist might enjoy using for a small 8-bit computer they’re experimenting with.

It relies on 7 pins to represent a 7-bit ASCII character and another pin that the connected device strobes in order to tell the Adam74 that there is a character waiting on the input pins to buffer and display. The prevalence of easy-to-interface small LCD displays and inexpensive microcontrollers to drive them made this project a no-brainer.

Like a terminal, the Adam74 handles wrapping of text, scrolling. It also handles many control codes like carriage return and bell. Other control codes are re-interpreted to give a simple cursor control interface, etc.

In doing research on the early terminals it was no surprise that I would stumble upon the ADM-3A terminal. And it will not surprise you that I drew inspiration from this machine for both the general shape of the acrylic stand I designed for it as well as the name itself.

The “74” in Adam74 is meant to suggest the era: sometime around 1974.

Here are the parts needed to populate the PCB:

  • Teensy 4.0 (PJRC)
  • Color 320×240 ILI9341-based LCD display (PJRC and other places)
  • 74LVC245 level shifter (Adafruit and other places)
  • Buzzer (Adafruit and other places)
  • 100 ohm, 1/4 Watt resistor (2×)
  • 0.1uF ceramic capacitor (3×) (Adafruit and other places)
  • 1N4148 small signal diode (Adafruit and other places)
  • 0.1″ male header pin strip (Adafruit and other places)
  • 20 pin (2×10, 2.54mm pitch) IDC male connector (optional)

The source code as well as Gerber files (and an SVG file you can use to cut the acrylic stand) are up on the EngineersNeedArt GitHub repo and the project described here.

 


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1 Comment

  1. Ricardo Bánffy

    Real shame the display is only 320×240. With a 640×480 one it’d be able to display a full 80×24 characters, just like a *real* ADM-3A.

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