Texas Instruments C28 Series User Manual

Function Descriptions
3.10 Real Fast Fourier Transform with ADC Input
Description:
This module computes a 32-bit floating-point real FFT with 12-bit ADC input including input bit
reversing. This version of the function requires input buffer memory alignment. If you do not
wish to align the input buffer, then use the RFFT_adc_f32u function.
Header File:
FPU.h
Declaration:
void RFFT_adc_f32 (RFFT_ADC_F32_STRUCT
*
)
Usage:
A pointer to the following structure is passed to the RFFT_adc_f32 function:
typedef struct {
Uint16
*
InBuf;
void
*
Tail;
} RFFT_ADC_F32_STRUCT;
typedef struct {
float32
*
InBuf;
float32
*
OutBuf;
float32
*
CosSinBuf;
float32
*
MagBuf;
float32
*
PhaseBuf;
Uint16 FFTSize;
Uint16 FFTStages;
} RFFT_F32_STRUCT;
Table 3.14 describes each element of the structure RFFT_ADC_F32_STRUCT and table 3.15
describes the elements of RFFT_F32_STRUCT, but note that its InBuf pointer is not used.
Item Description Format Comment
InBuf Input data Pointer to 16-bit Uint16 array Input buffer alignment is required. Re-
fer to the alignment section.
Tail Input structure Null pointer to RFFT_F32_STRUCT Null pointer is passed to OutBuf of
RFFT_F32_STRUCT.
Table 3.14: Elements of the Data Structure RFFT_ADC_F32_STRUCT
Alignment Requirements:
The input buffer must be aligned to a multiple of the 2*FFTSize. For example, if the FFTSize
is 512 you must align the buffer corresponding to InBuf to 2*512 = 1024. A smaller alignment
will not work.
To align the input buffer, use the DATA_SECTION pragma to assign the buffer to a code section
and then align the buffer to the proper offset in the linker command file. In this code example
the buffer is assigned to the INBUF section.
Sep 10, 2012 33

Texas Instruments C28 Series Specifications

General

Brand	Texas Instruments
Model	C28 Series
Category	Computer Hardware
Language	English