FFT API Reference#

Overview#

The current SDK exposes FFT to user applications through the RT-Smart HAL wrapper in drv_fft.h. The older public API described as kd_mpi_fft* and mpi_fft_api.h is no longer the application-facing interface in the current tree.

The current flow is:

Open the device with drv_fft_open().
Fill a drv_fft_cfg_t configuration.
Run FFT or IFFT through drv_fft_run(), drv_fft_fft(), or drv_fft_ifft().
Close the instance with drv_fft_close().

The HAL hides MMZ allocation, cache maintenance, and ioctl details from applications.

Public Types#

drv_fft_cfg_t#

typedef struct {
    uint32_t           point;
    k_fft_mode_e       mode;
    k_fft_input_mode_e input_mode;
    k_fft_out_mode_e   output_mode;
    uint16_t           shift;
    uint32_t           timeout_ms;
} drv_fft_cfg_t;

k_fft_mode_e#

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

k_fft_input_mode_e#

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

k_fft_out_mode_e#

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

Public Functions#

drv_fft_open#

int drv_fft_open(drv_fft_inst_t **inst);

Opens /dev/fft and returns an FFT instance handle.

drv_fft_close#

void drv_fft_close(drv_fft_inst_t **inst);

Closes the instance and clears the caller’s handle.

drv_fft_run#

int drv_fft_run(drv_fft_inst_t *inst, const drv_fft_cfg_t *cfg,
                const short *in_real, const short *in_imag,
                short *out_real, short *out_imag);

Runs one FFT or IFFT according to cfg->mode.

drv_fft_fft#

int drv_fft_fft(drv_fft_inst_t *inst, const drv_fft_cfg_t *cfg,
                const short *in_real, const short *in_imag,
                short *out_real, short *out_imag);

Convenience wrapper that forces FFT_MODE.

drv_fft_ifft#

int drv_fft_ifft(drv_fft_inst_t *inst, const drv_fft_cfg_t *cfg,
                 const short *in_real, const short *in_imag,
                 short *out_real, short *out_imag);

Convenience wrapper that forces IFFT_MODE.

Notes#

Supported point sizes are 64, 128, 256, 512, 1024, 2048, 4096.
in_imag may be NULL only when input_mode == RRRR.
timeout_ms = 0 disables timeout reporting and is the default used by current samples.
Return values follow negative errno-style error codes on failure.

Examples#

HAL roundtrip test: src/rtsmart/examples/peripheral/fft/test_fft.c
Audio spectrum display demo: src/rtsmart/examples/mpp/sample_fft_display/main.c

FFT API Reference

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