Why some keyboards have multiple HID devices anyway, I don't know. I have made a small 4 switch keypad and it can do 4 keys of input at once with a single HID keyboard device entry.īut I doubt more input devices is needed with the 120Hz polling rate ('input') for USB devices. The microcontroller in the keyboard is capable of a whole bunch of keystrokes at the same time (usually called 'rollover', like '5-key rollover' meaning it can do 5 keys at the same time and 'n-key rollover' usually meaning 'infinite' or 'more than practically possible' keystrokes). That is something I'd doubt, you're still limited to the 120Hz of the USB connection, no amount of extra HIDs will go above that. However I remember seing a comment in a facebook group where there is a dude explains that multiple HID keyboard devices means that the keyboard will able to process those key strokes at the same time.
