How did CD-i member TwBurn get the USB2CDi adapter to work without lag, considering the (very) slow communication of a CD-i player?

CD-i member TwBurn created the USB2CDi adapter so it is possible to use USB controllers on your CD-i player. In a recent interview on The World of CD-i he answered what the biggest difficulty was which he faced while developing this: "The biggest issue was getting the USB controllers to work without lag. The communication to the CD-i player is very slow (in the order of 40 updates/second) so the USB buffer would fill up while transmitting the current state, introducing “lag” – ie the cursor would keep moving for a bit even if you let go of the stick. In the end I solved this by implementing the communication to the CD-i player myself, instead of relying on a serial library. The serial library would block while transmitting, while my own code works of timer interrupts, which doesn’t block the execution of code."