The Tandy Color Computer came with analog joysticks, quite unlike most computers and consoles of the early 1980s. Many games of the era actually worked best with digital input, so [Gadget Reboot] whipped up a converter board to allow Nintendo gamepads to work with the computer.
The build relies on an earlier breakout board that [Gadget Reboot] built in order to read early Nintendo gamepads and output a digital 5 V signal. Meanwhile, the Tandy Color Computer is expecting variable o-5 V signals from the X and Y axis pots in its standard joysticks. To convert the gamepad button presses into voltages for the CoCo, the build uses a CD4066 analogue switch IC. When no controller buttons are pressed, the 4066 is set up to output 2.5 V on both the X and Y axes. Pressing up or down, or left or right on the D-pad, outputs 0 V or 5 V respectively as required. This essentially lets the controller’s D-pad act as a digital joystick for a computer that never actually had one.
It’s a neat hack that might make playing certain games on the Color Computer significantly easier. It’s also just neat to interface a different controller to the old hardware. In the early 80s, computers were simple enough that this could all be achieved with a minimum of dumb circuitry.
Thanks to [AnotherMaker] for the tip!