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Problem with the library "FastMath" function "rsqrtsp ()".

Rafael Werneck
Intellectual 270 points

3568.NewProject.zip

Hello

I am doing some simulations with the C6000 DSP family.  I am using the simulator CCS V4 (C674x CPU Cycle Accurate Simulator, Little Endian).

I am using the library "FastMath” (c67xmathlib_2_01_00_00) function “rsqrtsp_c()" to make the calculations of square roots.  But the calculations are incorrect.

The result of √100 = 10.  Using the "rsqrtsp_c ()" the result is: √100 = 0.1.

The result of √625 = 25.  Using the "rsqrtsp_c ()" the result is: √625 = 0.04.

Am I doing something wrong?

Attached there is a design example where this error happens.

Thanks

Rafael.

  • 0
    TI__Expert 8150 points

    Hello, the function is working correctly. Note, the function you are using gives reciprocal of sqrt (1/10 = 0.1; 1/25 = 0.04). 
    If you just want to get sqrt, use the function sqrtsp

    C:\c67xmathlib_2_01_00_00\src\sp\sqrtsp

    Cheers,
    Gagan 

  • 0 in reply to Gagan Maur
    Intellectual 270 points

     

    3362.NewProject.zip

     

    Hello Gagan.

    Thanks for your reply.

    I'm trying to use the function "sqrtsp” (. asm) but there is an error occurring.  This gives the following error on compilation:

    [E0200] Operation can not be Performed on Given operands                                                  line 0                                                        NewProject

    See the project attached.

    If I use the "sqrtsp_c ()" have no problem.

    What do I need to use the "sqrtsp.asm"?

    Thanks

    Rafael.

     

  • 0 in reply to Rafael Werneck
    TI__Expert 8150 points

    You need to add the below definition to your project options:

    __TI_EABI__=0

    Why don't you link in with the pre compiled libraries that are provided here:

    C:\c67xmathlib_2_01_00_00\lib

     

    Regards,
    Gagan