Real FFT Functions

Functions
void	csky_fft_lib_int16_ifft (q31_t log2_buf_len, q15_t *in_buf, q15_t *out_buf, const q15_t *twi_table, const twi_table_rfft_q15 *last_stage_twi_table, const uint16_t *bitrev_tbl, q15_t *temp_buf, q7_t *ScaleShift, q31_t br)
	Processing function for the Q15 real inverse FFT. More...
void	csky_fft_lib_int32_ifft (q31_t log2_buf_len, q31_t *in_buf, q31_t *out_buf, const q31_t *twi_table, const twi_table_rfft_q31 *last_stage_twi_table, const uint16_t *bitrev_tbl, q31_t *temp_buf, q31_t br)
	Processing function for the Q31 real inverse FFT. More...
void	csky_fft_lib_int16_fft (q31_t log2_buf_len, q15_t *in_buf, q15_t *out_buf, const q15_t *twi_table, const twi_table_rfft_q15 *last_stage_twi_table, const uint16_t *bitrev_tbl, q15_t *temp_buf, q7_t *ScaleShift, q31_t br)
	Processing function for the Q15 real FFT. More...
void	csky_fft_lib_int32_fft (q31_t log2_buf_len, q31_t *in_buf, q31_t *out_buf, const q31_t *twi_table, const twi_table_rfft_q31 *last_stage_twi_table, const uint16_t *bitrev_tbl, q31_t *temp_buf, q31_t br)
	Processing function for the Q31 real FFT. More...

Description

Brief Introduction

This is the real data part of the FFT library. Real FFT algorithms take advantage of the symmetry properties of the FFT and have a speed advantage over complex algorithms of the same length. Unlike the Original Method the forward transform, the inverse transform are seperated, so the ifftFlaga is not needed.More details can be seen in Real FFT Functions .

Algorithm

The algorithm used here is almost the same as the Original Method .

Initialization

Just like the CFFT, these is no need to initialize any instance structure, all the parameters and constants are passed to the related functions straightforwardly.

Function Documentation

void csky_fft_lib_int16_fft	(	q31_t	log2_buf_len,
		q15_t *	in_buf,
		q15_t *	out_buf,
		const q15_t *	twi_table,
		const twi_table_rfft_q15 *	last_stage_twi_table,
		const uint16_t *	bitrev_tbl,
		q15_t *	temp_buf,
		q7_t *	ScaleShift,
		q31_t	br
	)

Parameters

[in]	log_buf_len	log2 value of FFT size, the FFT size N is (1<<log2_buf_len)
[in,out]	*in_buf	point to the input and output memory
[in]	*out_buf	not used
[in]	*twi_table	point to the twi table
[in]	*last_stage_twi_table	point to the twi table
[in]	*bitrev_tbl	point to the bit reversal table
[in]	*temp_buf	not used
[in]	*ScaleShift	not used
[in]	br	bit reversal flag, always set

Returns

none.

Note

The time domin data and the frequency domain data are all in Q15 format, the forward transform is easy to overflow. So care to use it to avoid overflow.

void csky_fft_lib_int16_ifft	(	q31_t	log2_buf_len,
		q15_t *	in_buf,
		q15_t *	out_buf,
		const q15_t *	twi_table,
		const twi_table_rfft_q15 *	last_stage_twi_table,
		const uint16_t *	bitrev_tbl,
		q15_t *	temp_buf,
		q7_t *	ScaleShift,
		q31_t	br
	)

Parameters

[in]	log_buf_len	log2 value of FFT size, the FFT size N is (1<<log2_buf_len)
[in,out]	*in_buf	point to the input and output memory
[in]	*out_buf	not used
[in]	*twi_table	point to the twi table
[in]	*last_stage_twi_table	point to the twi table
[in]	*bitrev_tbl	point to the bit reversal table
[in]	*temp_buf	not used
[in]	*ScaleShift	not used
[in]	br	bit reversal flag, always set

Returns

none.

void csky_fft_lib_int32_fft	(	q31_t	log2_buf_len,
		q31_t *	in_buf,
		q31_t *	out_buf,
		const q31_t *	twi_table,
		const twi_table_rfft_q31 *	last_stage_twi_table,
		const uint16_t *	bitrev_tbl,
		q31_t *	temp_buf,
		q31_t	br
	)

Parameters

[in]	log_buf_len	log2 value of FFT size, the FFT size N is (1<<log2_buf_len)
[in,out]	*in_buf	point to the input and output memory
[in]	*out_buf	not used
[in]	*twi_table	point to the twi table
[in]	*last_stage_twi_table	point to the twi table
[in]	*bitrev_tbl	point to the bit reversal table
[in]	*temp_buf	not used
[in]	br	bit reversal flag, always set

Returns

none.

Note

The time domin data and the frequency domain data are all in Q31 format, the forward transform is easy to overflow. So care to use it to avoid overflow.

void csky_fft_lib_int32_ifft	(	q31_t	log2_buf_len,
		q31_t *	in_buf,
		q31_t *	out_buf,
		const q31_t *	twi_table,
		const twi_table_rfft_q31 *	last_stage_twi_table,
		const uint16_t *	bitrev_tbl,
		q31_t *	temp_buf,
		q31_t	br
	)

Parameters

[in]	log_buf_len	log2 value of FFT size, the FFT size N is (1<<log2_buf_len)
[in,out]	*in_buf	point to the input and output memory
[in]	*out_buf	not used
[in]	*twi_table	point to the twi table
[in]	*last_stage_twi_table	point to the twi table
[in]	*bitrev_tbl	point to the bit reversal table
[in]	*temp_buf	not used
[in]	br	bit reversal flag, always set

Returns

none.