Changes
The interface is based on the WCH CH376 chip and allows access to USB mass storage and other USB devices on CPC.
The CH376 chip implements FAT32 in hardware, which means no filesystem driver is needed on the CPC side. This makes it very easy to use the interface with a microSD card, USB stick or hard drive and access files on the FAT32 partition directly, without using a lot of CPU power or memory on the CPC.
It also implements the lower level aspects of USB, making it relatively easy to write drivers for other USB devices (mouse, joystick, ...). It is simple enough that the mouse driver was initially written completely in BASIC.
