This profiler is somewhat limited because it can only see the top function that was executing when it takes a sample. It doesn’t currently have the ability to look up the stack and see which functions were responsible for calling the function that was interrupted. Our results will be the same, and CPU sampling overhead will decrease. If the profiler slows down the CPU too much, we only have to reduce our sampling rate and sample for longer. In this way we can construct an accurate picture of the program with a nice constant overhead. If one piece of code accounts for 30% of the execution time of the program, then we should expect 30% of our random samples to end up seeing that line of code being run. The checks can be used to measure what percentage of the time is spent on each line of code in the program. The profiler makes 1000 of these checks per second and sends the results out to a serial port to be logged. A sampling profiler works by periodically interrupting the program’s execution to check what code is currently running. In order to find out, I built a Sampling Profiler feature for Cleanflight.

It’s not heavily used in any other parts of the code.īut 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? 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. 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. 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. 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.

Cleanflight firmware for stm32f3