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Zephyr project on STM32

   Zephyr Workbench, a VSCode extension to manage Zephyr on STM32.
It enables users to easily create, develop, and debug Zephyr applications.
Main features:
  • Install host dependencies.
  • Import toolchain and SDK.
  • Create, configure, build and manage apps.
  • Debug STM32.
You can directly download it from the VSCode marketplace
For more details, visit the Zephyr Workbench

System Workbench for STM32

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You are viewing a reply to [solved] FPU going too slow  

FPU going too slow

Posted by florentEc on 2016-05-06 13:05

Hi Bernard.
Thank you very much for all these clarifications, I understand much better now! I am gonna do some experimentation with moving some parts to RAM and post the results here (if there are any conclusive results).

About the FLASH_ACR register, I should : set DCRST and ICRST, *then* set the 3 bits to enable prefetching?
Last thing, you said that STM32F411 had 0 wait state at any clock frequency (and I’ve read that on the product page as well). That means that 100 MHz IS indeed the best solution to go fast, right? I don’t have to determine the best clock value given that increasing the clocking speed will not induce any more wait state? This leads me to another question : why would someone run the F411 (or other) slower than 100 MHz if it’s 0 wait state at 100 MHz? My first thought was power consumption, it might make a significant difference... Are there any other criterias?

Thanks a lot for your help,

Florent

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Posted by dautrevaux on 2016-05-06 22:13 France

Hi Florent,

Yes the main reason to run slower may be to save power; however if you carefully use WFI (or WFE) for sleeping when you don’t have anything to do (waiting to be woken up by some interrupt, even masked for WFI, only unmasked ones for WFE) then you may achieve about the same power consumption at 100MHz, but have better response times due to the higher CPU frequency.

Of course this is only valid if you are interrupt-driven; if you use polling, you can’t use WFI/WFE and then decreasing teh CPU frequency to what gives you the needed performance will provide you with better battery life.

Bernard (Ac6)

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