With the recent release of the SPRacingF3 flight controller and the Seriously Dodo flight controller, both based on the newer STM32 F3 CPU, users have been posting great Blackbox flight logs demonstrating very fast and consistent looptimes. I found this interesting because the F3’s CPU isn’t clocked any faster than the F1 processor that is used on the Naze32 and compatibles.
One major difference between these CPUs is that the F3 has a hardware floating point unit, while the F1 must emulate its floating point support using some very large software routines. Floating point support is used in the IMU (which is responsible for estimating the craft’s attitude) and also as part of some PID controllers such as the new Harakiri controller. It’s not heavily used in any other parts of the code.
But how much time does the Naze32 spend doing floating point operations anyway? What is the total possible speedup available from just adding a hardware floating point unit? Could I speed my Naze32 up some other way?