This small circuit is for testing C64 keyboards, it measure with a AVR uC ATTINY85 the resistance of a keypress. under a treashold of 800Ohm - a red led goes on a green led show a startet uC
so its possible to check if a key on the keyboard makes some trouble, the treshold is at 800 Ohm , a press on a C64 is mormaly detect under 1kOhm the ATTINY85 works with internal clock at 1Mhz
This repository contains all Autodesk Eagle files, gerber file, BOM, schematics, a small Arduino source code, Hex File for ATTINY85, Projekt File for XGeco T48-3 Eprom Programmer for Firmware
STL and CAD Files for a minimal enclosure,
Depending on where the parts and pcbs are purchased, the price for the complete circuit is around 5€ (2023), without enclosure and power supply