help : about DSPLIB

fagang yan

I wonder the type of "DATA" in the DSPLIB. Is it Q. 15 or Q15 ?

I see that DATA is defined as short type in the related material.

I think the short type is equal to Q15 type.

but from the routine using the DPSLIB in the ccs installing folder , the result is right if wo consider "DATA" as "Q. 15",and it is wrong if wo consider "DATA" as "short".

So i don't know how can I define the variable in a c program if i want to use the DSPLIB.

Thank you very much.

over 12 years ago

0 Mark M over 12 years ago

TI__Mastermind 30140 points

Hi,

in DSPLIB, the data type for DATA is Q.15 (DATA) : A Q.15 operand is represented by a short data type (16 bit) that is predefined as DATA, in the dsplib.h header file.

The short data type just means 16-bits... It is up to the software to realize that the data stored is in the Q.15 format...

For other DSPLIB routines like cfft32, 32-bits are used to store Q.31 (LDATA) data in a long data type (32 bit)

See 3.1 DSPLIB Arguments and Data Types in http://www.ti.com/lit/ug/spru422j/spru422j.pdf

See Appendix A: Overview of Fractional Q Formats in http://www.ti.com/lit/ug/spru422j/spru422j.pdf

See 5.4 Data Types in http://www.ti.com/lit/ug/spru281g/spru281g.pdf

Hope this helps,
Mark

0 fagang yan over 12 years ago in reply to Mark M

Prodigy 20 points

Your earnest reply is very helpful for me.Thank you very much!

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help : about DSPLIB