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    • Enable FPU in System Workbench for STM32

    Posted by filartrix on 2015-01-28 14:09

    Hi all,
    It would be great to enable Hardware FPU on F4 devices.
    Which compiler flags or directives need to be enabled?
    Thank you
    Filippo

    Reads: 33912
    Posted by gvigelet on 2015-01-29 17:54

    Hi Filippo,

    I had this problem a while back using codesourcery, the flags that need to be enabled are

    -mfpu=fpv4-sp-d16 -mfloat-abi=softfp

    There was also an issue with the toolchain, I ended up switching it to the launchpad gnu arm toolchain with much success. I don't know if this is even an issue with this toolchain since I have not tested it. If I get a chance I will create a project and try it out.

    Thanks,
    George


         Posted by filartrix on 2015-02-01 12:10

    Hi George,
    than you for the tip.
    I made some tests and I tried your solution, it works!
    Anyway I've been reading the difference between:

    • [+]mfloat-abi=soft (software emulated floating point)
    • [+]mfloat-abi=softfp (uses FPU instructions, keep compatiblity with non "soft" libraries, but data are loaded into the FPU in a slower way)
    • [+]mfloat-abi=hard (best performances, but not compatible with object not generated using hard flag)

    https://wiki.debian.org/ArmHardFloatPort/VfpComparison
    so when possible hard flag should be used.
    If the projct does not use external libraries, is possible to use "hard" flag, but the flag has to be enabled in: GCC compiler, GCC Linker and GCC Assrmbler.
    To do so, go to project properties (Alt + Enter), choose C/C++ Build and then settings, then add flags:
    http://s16.postimg.org/olvegtf05/Untitled.png

    Bye Filippo

    Posted by dautrevaux on 2015-02-02 11:06 France

    Hi Filippo,

    To add this kind of options, rather than modifying directly the command line pattern, it is better to change the "additionnal flags" in the "Miscellaneous" tab.

    For the FPU settings, in a forthcoming update they will be available in the "MCU Settings" tab, with the FPU kind and ABI preselected depending on the MCU chosen when creating the project.

    Bernard