ZX Spectrum Game Loader Has Joystick Pass-Through

The first generation of home computers, back in the time of 8-bit processors, came with only ROM (Read-Only Memory) where the operating system resided. There were no built-in hard drives where you could install software. Instead, you loaded the entirety of your software into the computer's RAM. While external floppy disk drives soon became common external accessories, most computers of the era loaded software from cassette tapes. Today, you can load software onto vintage computers by playing the right audio file from a digital source, like a smartphone. TZXDuino is a dedicated hardware device for the job, and JamHamster built a version with a joystick pass-through.

A TZXDuino is a small Arduino Nano-based device that pumps selected program audio files out to vintage computers, such as the legendary ZX Spectrum. We've covered a couple of unique TZXDuino projects in the past, but this one stands out because of the addition of the joystick pass-through. Normally, you have to use small buttons on the TZXDuino device to select the program you want to load from those stored on the SD card. This version reads the signals from the joystick, so Jamhamster can use that to select the program to load.

Most of the hardware that went into this project is the usual for a TZXDuino build. It has an Arduino Nano board, a small 0.96" OLED screen, an SD card module, an audio amp with headphone jack, and a slide switch. But this version adds one very important component: a female DB9 port. Standard Spectrum-compatible joysticks plug into that DB9 port. The Arduino monitors the DB9 pins to determine when the joystick is moved or buttons are pressed in order to navigate through the TZXDuino menu. The male DB9 cable also connects to those pins, so joystick commands pass through to the ZX Spectrum and games play like normal.

Jamhamster crammed all of that hardware into a tiny plastic enclosure. They trimmed that enclosure so the screen is visible on top, then they gave it a rainbow stripe paint job to match the ZX Spectrum's iconic graphics. This is a minor improvement over the standard TZXDuino, but it makes using the device more pleasant.