PS/2 keyboard adapter for ZX Spectrum on Atmega328 + EPM7128STC100. Designed to be connected directly instead of a mechanical keyboard.
Based on the idea of the Yet another ZX-Spectrum AT Keyboard Interface http://www.jrok.com/project/speckey/spec_key.html
- disconnect EPM7128 from the power source by disconnecting jumper JP1
- avrdude -p atmega328p -c USBasp -U flash:w:avr_kbd_mega328p.hex -U lfuse:w:0xbf:m -U hfuse:w:0xda:m -U efuse:w:0xfd:m
- short JP1
use quartus programmer to flash cpld_kbd.pof
- Ctrl+Alt+Del generate a short negative pulse on O_RESET pin. It's nice to connect this signal to N_RESET of your ZX Spectrum
- Ctrl+Alt+Backspace produce a controller internal reset needed for some reason
- F2 generate a short negative pulse on O_MAGICK pin. If you have a BDI controller then you have to connect this signal to magick button.
- Scroll Lock switch on / off the O_TURBO signal
- PrintScreen switch on / off the O_SPECIAL signal