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TMS320F28335 - Calc trigonometric functions with the FPU on board

Chris M.
Intellectual 330 points


Hi @ all,

i want to use the FPU hardware on board, to calculate some trigonometric functions (sin/cos, only singe precision/ float).

I will set the setting of CCS4, as shown in the Example_2833xFPU_hardware.

Must I use the header "math.h" to calculate trigonometric functions fast with the FPU on board, too?

Are there some examples?

 

Best regards,

Chris

 

  • 0
    TI__Mastermind 20850 points

    Chris,

    When you setup your project make sure you pull in the rts2800_fpu32.lib runtime support library. This will have floating point routines for all the trig functions. You will need to include math.h in your project.

    I dont think there are any examples that are specific to math.h. But again this is an ANSI C library so the standard functions will be supported.

     

  • 0 in reply to Vishal_Coelho
    TI__Mastermind 20850 points

    Also you have to turn on fpu support in the project properties under the "Run Time Support" Option

  • 0 in reply to Vishal_Coelho
    Intellectual 690 points

    There is a fast supplemental library that can be linked in.  Helps with atan, cos, sin, sqrt, and div.  I had to use this with a fast ISR in order to get the execution time down.

     

    rts2800_fpu28_fast_supplement.lib

  • 0 in reply to Christopher Taylor
    Intellectual 330 points

    Good morning,

    thank you for reply my questions!

    First of all I have set the properties as follows:

     

    I hope thats correct?

    These are all properties i have set.

    Another point is, that the header "math.h" use variables of the type double. I think that reduce the speed of calculation!?

     

    Ok, and then i have read the Module User’s Guide (C28x_FPU_FastRTS_v10) and asking me, what is the advantage of the C28x_FPU_RTS?

    Related to the IQMath library, the calculation of sin/cos is not much faster:

    !Fast! FPU

    !IQ_MATH

     

    Why do I need a FPU, although the calculation time is similar to the fixed point?

     

    With best regards,

    Chris

  • 0 in reply to Chris M.
    Mastermind 7585 points

    Your link order is incorrect. You should have the supplement lib first in the sequence.

    The rts fast lib is also faster when you use floating point variables. For example, a calculation of y=sin(x) will use the float sin - lookup table in ROM instead of calling a library function to calculate the value.