K230 FFT API Reference

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[TOC]

preface

Overview

This document mainly introduces the API of K230 FFT, including API usage and test program introduction.

Reader object

This document (this guide) is intended primarily for:

• Technical Support Engineer

• Software Development Engineer

Definition of acronyms

abbreviation	illustrate
FFT	Fast Fourier Transform, a fast algorithm for discrete Fourier transforms
IFFT	Inverse fast Fourier transform

Revision history

Version	Description	Author	date
V1.0	Initial edition	Wang Jianxin	2023-08-08

Introduction to the K230 FFT

The FFT module of K230 is mainly used for hardware-accelerated FFT and IFFT calculations, and its characteristics are as follows:

Support 64, 128, 256, 512, 1024, 2048, 4096 point FFT, IFFT calculation. Support int16 calculation accuracy, that is, the real and imaginary parts of the input and output are in INT16 format. Supports the standard AXI4 slave interface, which is used for parameter configuration and data migration. Input support RIRI…., RRRR…., RRRR… IIII… Format arrangement, output support RIRI…., RRRR… IIII… Format arrangement. Using the basis 2-time decimation calculation method, there is only one butterfly operator inside. With a single-clock domain design, the bus clock is also used as an arithmetic clock to save overhead across clock domains. The calculation time of 4096-point FFT/IFFT is controlled within 1ms, including the total overhead of data migration, calculation, and interrupt interaction. Supports interrupt mask and raw interrupt query.

API Reference

The k230 FFT module mainly provides the following APIs:

• kd_mpi_fft_or_ifft

• kd_mpi_fft_args_init

• kd_mpi_fft_args_2_array

• kd_mpi_fft

• kd_mpi_ifft

kd_mpi_fft_or_ifft

【Description】

FFT or IFFT computes core functions.

【SYNOPSIS】

int kd_mpi_fft_or_ifft(k_fft_args_st * fft_args);

【Parameters】

Parameter name	description	Input/output
fft_args	k_fft_args_st	Input/output

【Return value】

Return value	description
0	Succeed.
other	fail

【Differences】

None

【Requirement】

• Header file: mpi_fft_api.h

• Library file: libfft.a

【Note】

None

【Example】

int kd_mpi_fft(int point , k_fft_input_mode_e im,  k_fft_out_mode_e om,
                k_u32 timeout , k_u16 shift ,
                short *rx_in, short *iy_in, short *rx_out, short *iy_out)
{
    int ret = 0 ;
    k_fft_args_st fft_args;
    ret = kd_mpi_fft_args_init(point, FFT_MODE , im, om, \
                 timeout,  shift,   rx_in, iy_in , &fft_args); ERET(ret);
    ret = kd_mpi_fft_or_ifft(&fft_args); ERET(ret);
    ret = kd_mpi_fft_args_2_array(&fft_args, rx_out, iy_out);ERET(ret);
    return 0;
}

【See Also】

None

kd_mpi_fft_args_init

【Description】

fft_args initialization (helper functions)

【SYNOPSIS】

int kd_mpi_fft_args_init( int point,  k_fft_mode_e mode,  k_fft_input_mode_e im,
                          k_fft_out_mode_e om,    k_u32 timeout ,    k_u16 shift,
                          short *real, short *imag, k_fft_args_st *fft_args );

【Parameters】

Parameter name	description	Input/output
point	Points, valid values are 64, 128, 256, 512, 1024, 2048, 4096	input
mode	k_fft_mode_e FFT_MODE IFFT_MODE	input
in	k_fft_input_mode_e Input Mode	input
to	k_fft_out_mode_e	input
time_out	Timeout	input
shift	offset	input
rx_input	Enter real data	input
iy_input	Enter imaginary data	input
fft_args	k_fft_args_st Variables to populate	output

【Return value】

Return value	description
0	Succeed.
other	fail

【Differences】

None

【Requirement】

• Header file: mpi_fft_api.h

• Library file: libfft.a

【Note】

None

【Example】

int kd_mpi_fft(int point , k_fft_input_mode_e im,  k_fft_out_mode_e om,
                k_u32 timeout , k_u16 shift ,
                short *rx_in, short *iy_in, short *rx_out, short *iy_out)
{
    int ret = 0 ;
    k_fft_args_st fft_args;
    ret = kd_mpi_fft_args_init(point, FFT_MODE , im, om, \
                 timeout,  shift,   rx_in, iy_in , &fft_args); ERET(ret);
    ret = kd_mpi_fft_or_ifft(&fft_args); ERET(ret);
    ret = kd_mpi_fft_args_2_array(&fft_args, rx_out, iy_out);ERET(ret);
    return 0;
}

【See Also】

None

kd_mpi_fft_args_2_array

【Description】

Convert FFT output to arrays (auxiliary functions for easy printing).

【SYNOPSIS】

int kd_mpi_fft_args_2_array(k_fft_args_st * fft_args, short *rx, short *iy);

【Parameters】

Parameter name	description	Input/output
fft_args	k_fft_args_st	input
rx_out	Real data	output
iy_out	Imaginary data	output

【Return value】

Return value	description
0	Succeed.
other	fail

【Differences】

None

【Requirement】

• Header file: mpi_fft_api.h

• Library file: libfft.a

【Note】

None

【Example】

int kd_mpi_fft(int point , fft_input_mode_e im,  fft_out_mode_e om,
                k_u32 timeout , k_u16 shift ,          k_u16 dma_ch,
                short *rx_in, short *iy_in, short *rx_out, short *iy_out)
{
    int ret = 0 ;
    fft_args_st fft_args;
    ret = kd_mpi_fft_args_init(point, FFT_MODE , im, om, \
                 timeout,  shift, dma_ch,  rx_in, iy_in , &fft_args); ERET(ret);
    ret = kd_mpi_fft_or_ifft(&fft_args); ERET(ret);
    ret = kd_mpi_fft_args_2_array(&fft_args, rx_out, iy_out);ERET(ret);
    return 0;
}

【See Also】

None

kd_mpi_fft

【Description】

FFT calculation,

The core is kd_mpi_fft_args_init, kd_mpi_fft_or_ifft, and kd_mpi_fft_args_2_arra three functions packaged together for easy use.

【SYNOPSIS】

int kd_mpi_fft(int point , k_fft_input_mode_e im,  k_fft_out_mode_e om,
                k_u32 timeout , k_u16 shift ,
                short *rx_in, short *iy_in, short *rx_out, short *iy_out);

【Parameters】

Parameter name	description	Input/output
point_num	Points, valid values are 64, 128, 256, 512, 1024, 2048, 4096	input
in	fft_input_mode_e Input Mode	input
to	fft_out_mode_e	input
time_out	Timeout	input
shift	offset	input
rx_input	Enter real data	input
iy_input	Enter imaginary data	input
rx_out	Calculate the resulting real data	output
iy_out	Calculation results: imaginary data	output

【Return value】

Return value	description
0	Succeed.
other	fail

【Differences】

None

【Requirement】

• Header file: mpi_fft_api.h

• Library file: libfft.a

【Note】

None

【Example】

static int fft_test(int point)
{

    test_build_fft_org_data(point, i_real, i_imag);

    //soft_fft_ifft_calc(point);
    clock_gettime(CLOCK_MONOTONIC, &begain_time);
    kd_mpi_fft(point,   RIRI,RR_II_OUT, 0, 0x555,  i_real, i_imag, o_h_real, o_h_imag);
    clock_gettime(CLOCK_MONOTONIC, &fft_end);
    kd_mpi_ifft(point,  RIRI,RR_II_OUT, 0, 0xaaa,  o_h_real, o_h_imag, o_h_ifft_real, o_h_ifft_imag);
    clock_gettime(CLOCK_MONOTONIC, &ifft_end);
    display_calc_result(point);

    return 0;
}

【See Also】

None

kd_mpi_ifft

【Description】

IFFT calculation

The core is kd_mpi_fft_args_init, kd_mpi_fft_or_ifft, and kd_mpi_fft_args_2_arra three functions packaged together for easy use.

【SYNOPSIS】

int kd_mpi_ifft(int point , k_fft_input_mode_e im,  k_fft_out_mode_e om,
                k_u32 timeout , k_u16 shift ,
                short *rx_in, short *iy_in, short *rx_out, short *iy_out);

【Parameters】

Parameter name	description	Input/output
point_num	Points, valid values are 64, 128, 256, 512, 1024, 2048, 4096	input
in	fft_input_mode_e Input Mode	input
to	fft_out_mode_e	input
time_out	Timeout	input
shift	offset	input
dma_ch	DMA channels 0-3 are valid; other values are illegal	input
rx_input	Enter real data	input
iy_input	Enter imaginary data	input
rx_out	Calculate the resulting real data	output
iy_out	Calculation results: imaginary data	output

【Return value】

Return value	description
0	Succeed.
other	fail

【Differences】

None

【Requirement】

• Header file: mpi_fft_api.h

• Library file: libfft.a

【Note】

None

【Example】

static int fft_test(int point)
{

    test_build_fft_org_data(point, i_real, i_imag);

    //soft_fft_ifft_calc(point);
    clock_gettime(CLOCK_MONOTONIC, &begain_time);
    kd_mpi_fft(point,   RIRI,RR_II_OUT, 0, 0x555,  i_real, i_imag, o_h_real, o_h_imag);
    clock_gettime(CLOCK_MONOTONIC, &fft_end);
    kd_mpi_ifft(point,  RIRI,RR_II_OUT, 0, 0xaaa,  o_h_real, o_h_imag, o_h_ifft_real, o_h_ifft_imag);
    clock_gettime(CLOCK_MONOTONIC, &ifft_end);
    display_calc_result(point);

    return 0;
}

【See Also】

None

Data structure

The relevant data types for this function module are defined as follows:

• k_fft_args_st

• k_fft_mode_e

• k_fft_input_mode_e

• k_fft_out_mode_e

k_fft_args_st

【Description】FFT IOCTL parameter

【Definition】

typedef union
{
    struct {
        volatile fft_point_e point:3; //2:0  0:64;1:128;2:256;3:512;4:1024;5:2048;6:4096
        volatile k_fft_mode_e mode:1;  //3 0:fft 1:ifft
        volatile k_fft_input_mode_e im:2; //5:4 0:RIRI....;1:RRRR...;2:RRRR...IIII..
        volatile k_fft_out_mode_e om:1; //6 0:RIRI....;1:RRRR...IIII...
        volatile k_u64 fft_intr_mask : 1;//7 0:not mask intr; 1:mask intr
        volatile k_u16 shift:12; //19:8
        volatile k_u32 fft_disable_cg : 1;//20 write 1 disable fft clock gating
        volatile k_u32 reserv : 11 ;//31:21
        volatile k_u32 time_out:32;//63:32
    }__attribute__ ((packed));
    volatile k_u64 cfg_value;
} __attribute__ ((packed)) k_fft_cfg_reg_st;


typedef struct {
    k_fft_cfg_reg_st reg;
    k_char rsv[4];
    k_u64 data[FFT_MAX_POINT*4/8]; // input and output;
}k_fft_args_st;

【Members】

Member Name	Description
reg	The configuration register value of the FFT
data	Input and output data of FFT

【Note】

None

k_fft_mode_e

【Description】FFT IOCTL parameter

【Definition】

typedef enum  {
    FFT_MODE = 0,
    IFFT_MODE,
}k_fft_mode_e;

【Members】

Member Name	**** Description
FFT_MODE	fft
IFFT_MODE	ifft

【Note】

None

k_fft_input_mode_e

【Description】FFT IOCTL parameter

【Definition】

typedef enum {
    RIRI = 0,
    RRRR,
    RR_II,
} k_fft_input_mode_e;

【Members】

Member Name	Description
RI	RIRI format data
RRRR	RRRR solid data
RR_II	RR_II format data

【Note】

none

k_fft_out_mode_e

【Description】FFT IOCTL parameter

【Definition】

typedef enum {
    RIRI_OUT = 0,
    RR_II_OUT,
} k_fft_out_mode_e;

【Members】

Member Name	Description
RIRI_OUT	RIRI format data
RR_II_OUT	RR_II format data

【Note】

None