How to use DSP instructions on Kinetis K66 MCU?

[giova841]

Hi everybody,

I have written a program on the K65 MCU which performs some controls and a few calculations. Looking at execution times I found out that the calculations performed were the instructions that took the most time.

These calculations are simple multiplications between float variables and I think that some micro-seconds for each multiplication is really too high, considering I have a 120 MHz clock! probably there is something missing in my code or there are some compiler options which I have not set properly so I am asking you:

• is there any compiling options I can enable in order to use the math co-processro provided with the ARM -M4?
• is there any libraryI can laod to use the "DSP Instructions" described in the ARM -M4 reference guide?

Cheers,

Giulio

[mjbcswitzerland]

Hi

Do you compiler for HW  FPU use?

These flags are needed by GCC:

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

Regards

Mark

[giova841]

Yes, these are my compiler settings:

[Hui_Ma]

Hi

Besides to set the compiler, it also need to enable FPU with below code:

; Enable the floating point coprocessor

#if defined (_VFPv4_)

      MOVW r1,#60808              ; load CPACR            

      MOVT r1,#57344              ; (0xE000ED88) 

      LDR r0,[r1]

      ORR.W r0,r0,#VFPEnable      ; Enable FPU

      STR r0, [r1]                ; on CP10, CP11

      MOV.W r0,#R2N_Enable

      VMSR FPSCR, r0

#endif 

Wish it helps.

Have a great day,
Ma Hui
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