With FTDI245, the application is required to write the data into a FIFO, which is then emptied from time to time by the whole USB chain - look at it as the PC "sucks" it from time to time. So, it is your hardware (theoretically a simple oscillator would suffice) which dictates the tempo; the caveat is, that under heavy load the data might get lost (the FIFO overflows prior the OS/software/USB chain empties it) but it is easy to detect - just hang a flipflop on the "receiver ready" signal of the chip.

So it IS a good idea, perhaps requiring the least time to make it working - provided that you have the chip on hand.

Jan Waclawek