PIC16F1459 solution for converting old AT (PS/2) keyboard to USB.
Schematic and one layer PCB can be found under hardware directory.
The hardware design is created using KiCad 7.0.
The circuit is very simple and it can be created easily on prototyping board.
The firmware is developed with MPLAB X IDE, found under at2usbClassic.X directory.
USB stack implementation and main HID app code is based on USB HID keyboard project from Microchip Libraries for Applications (MLA).