The ultimate partner for the HP Prime G2 - The Arduino Leonardo.

[gehakte_bits]

The ATmega32U4 (watch for the 'U') in the Leornardo micro/pro family supports the USB-HID with its build-in USB controller as matalog shows.

Matalog's current solution provides a simple method to send/receive raw USB HID data (like a keyboard or a mouse) with some additional Arduino USB-HID coding (in addition to the HP Prime programming) to/from a single sensor/port.

The FT260 requires a command opcode/data length in its protocol to address multiple devices at once, as well as header overhead reduction (speed) (i.e. multiple sensors/sound generators/modems on the I2C bus, or serial data vs interrupt differentiation). That makes the FT260 protocol a bit more complex.

The Micro Leornardos have enough memory to add proper (configuration/queues/priority handling..) bridge software to redirect/translate from all their I/O to/from the USB-HID port, but that requires the development/maintenance of Arduino software. Now you are in the Arduino development world ...