creating a LUT (look-up table)

Francesco Fraccaroli

Hi all

I need to create a lookup table of sine function in my application. I'm working on F2812. Does anybody ever do it? How can I do this?

I tried allocating a vector in the main program, in a library or in another function , but I have problem of memory (see my previous post). Now I try to allocate it in RAM allocating directly in the main program, but I have one problem: all location of the vector contains -1.

Anybody have experience this?

PS: I can't (and won't) use IQ libraries, because I need a 5000-length table and I use integers.

Francesco

over 13 years ago

0 Francesco Fraccaroli over 13 years ago

Prodigy 120 points

Hi all

PROBLEM SOLVED!!

If you want to create a LUT ad mem it in ROM or FLASH, you have to define a memory location in the .cmd file, as say in http://e2e.ti.com/support/microcontrollers/tms320c2000_32-bit_real-time_mcus/f/171/t/154414.aspx and use the directive #pragma to indicated where you want to allocate the vector.

If the vector is allocated in RAM there is no problem, but if it has to be allocated in ROM or FLASH, it has to be defined "const", so the linker understand that the vector has to be written at memory writing. If you don't do that, the vector not contains your data, but casual numbers (if ROM) or -1 (idf FLASH).

So, the declaration of the vector has to be (for example):

const int sinLUT[length_SINLUT] = {...};

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creating a LUT (look-up table)