Arduino for STM32

try something like a stm32 f4xx (e.g. stm32f401 / f411 ) board, those has the FPU, but that it is for floats only.

other things to try are to move the computation codes into loop() and only use the ISR callback to simply count cycles, e.g. increment a global variable.

PC14 OSC32_IN PC15 OSC32_OUT is normally used for a 32 khz crystal for the RTC. it is probably not a good idea to use them as gpio ports. e.g. there is likely a 'not gate' connecting PC14 to PC15 with some extra stuff. that 'not gate' is literally used as an amplifier, given sufficient conditions e,...

The trouble with operating in 32 bits is you need a gcc-none-eabi compiler built for 32 bits. Fortunately, they are there https://developer.arm.com/downloads/-/gnu-rm and not least, you need the full suite of glibs and libs that gcc runs on, along with any libs that the rest of the tools depends on....

dannyf I think the op kind of mentions that stm32g071 timers can do 128 Mhz. it is something quite interesting to explore, that is practically VHF, FM radio frequencies if you noted. in a sense if that is possible, even for that matter use it as an oscillator, mix it with FM radio waves from an ant...

assuming that you are using stm32f103. I think in stm32f103 the timers are 16 bits. but that it has a prescaler which is 16 bits I've not reviewed the codes really. But that keep rm0008 handy as it tells you what is ultimately available in the hardware. https://www.st.com/resource/en/reference_manua...

128 Mhz is probably above the cpu clock frequency e.g. for stm32f103c8 72 Mhz, you can probably at best get like 72 Mhz or more commonly half or less like 36 Mhz. for the 'official' STM core, the wiki is here https://github.com/stm32duino/Arduino_Core_STM32/wiki hardware timer API is documented here...

for this board/chip, note that you would need the 'official' STM core https://github.com/stm32duino/Arduino_Core_STM32 https://github.com/stm32duino/Arduino_Core_STM32/wiki in part has it has the full STM32 HAL stack in tow, a fat footprint, but that is the reason the 'support' is bundled. and you c...

happy new year

it may work if you #include "todayLib.c" instead ( of "todayLib.h" )

Accordingly, tolerant pins have diodes that sink currents, but they still require a high enough resistor to limit the currents going into the pin.
For non-tolerant pins you are taking your chances
http://www.emcu.eu/000/STM32_5VtolerantIO.pdf