Hi all,
To prove that my code was configuring the systick counter correctly, I did a small test. To measure the interval length between each SysTick interrupt handler I used SWV in combination with my IDE (Atollic TRUEStudio), which provides a clock tick count for whenever the microcontroller enters or leaves the handler.
Now the silly thing, I am missing clock cycles. Depending on both the system clock frequency and the configured interval between the Systick interrupts I am missing clock cycles, hence the interval is shorter then expected. For a high clock frequency and short Systick interval, I am not missing any clock cycles, but for a low frequency with a longer systick interval I am missing up to 7 clock cycles.
As this is hardware and fairly simple to use I assume I either oversaw something or my measurement technique is not accurate. Does anyone has an idea?
I'm new here, but if you want precision measurements, the classic way is to use an interrupt to toggle a port bit, then use a scope or counter on that to measure the interval. Who knows what might be happening inside a toolchain...