Adapter for using Sega Master System HPD-200 paddle controller with [Kempston] (https://en.wikipedia.org/wiki/Kempston_Interface) interface. Test programs are provided for ZX81 and Speccy. Hackaday.io page
Provides quick and dirty matrix keyboard emulator to complement ZX-80/81 and ZX Spectrum boards. The whole project is built around an Arduino Nano board and one (optional) diode. Hackaday.io project page