This is a fully functional keyboard switch (KVM but while only the keyboard), based on the combination of Arduino UNO + Arduino LEONARDO pro Micro. Arduino UNO sends data from a connected USB keyboard via SoftwareSerial to 2 Arduino LEONARDOs that emulate the keyboard.
Keyboard is toggled with ScrollLock Key. I recommend USB cable keyboard. All SoftwareSerials has baud rate: 38400 (increased to 115200)
Connection Schematics:
Prototype photo:
to do mouse/joypad/video switch support...
USB version has been released: https://github.com/nathalis/Arduino-USB-KM-Swtich
by Nathalis.
MIT. License (c)2020