Collaboration diagram for Real FFT Functions:

Functions
tpt_status	tpt_rfft_f32 (f32_t aOutData, f32_t aInData, size_t aLogN, bool aIfftFlag)
	Processing function for the floating-point RFFT/RIFFT. More...

tpt_status	tpt_rfft_f64 (f64_t aOutData, f64_t aInData, size_t aLogN, bool aIfftFlag)
	Processing function for the floating-point RFFT/RIFFT. More...

tpt_status	tpt_rfft_q15 (q15_t aOutData, q15_t aInData, size_t aLogN, bool aIfftFlag)
	Processing function for the Q15 RFFT/RIFFT. More...

tpt_status	tpt_rfft_q31 (q31_t aOutData, q31_t aInData, size_t aLogN, bool aIfftFlag)
	Processing function for the Q31 RFFT/RIFFT. More...

Detailed Description

: The DSP library includes specialized algorithms for computing the FFT of real data sequences. The FFT is defined over complex data but in many applications the input is real. Real FFT algorithms take advantage of the symmetry properties of the FFT and have a speed advantage over complex algorithms of the same length.

: The Fast RFFT algorithm relays on the mixed radix CFFT that save processor usage.

: The real length N forward FFT of a sequence is computed using the steps shown below.

: Real Fast Fourier Transform

: The real sequence is initially treated as if it were complex to perform a CFFT. Later, a processing stage reshapes the data to obtain half of the frequency spectrum in complex format. Except the first complex number that contains the two real numbers X[0] and X[N/2] all the data is complex. In other words, the first complex sample contains two real values packed.

: The input for the inverse RFFT should keep the same format as the output of the forward RFFT. A first processing stage pre-process the data to later perform an inverse CFFT.

: Real Inverse Fast Fourier Transform

: It supports lengths of [32, 64, 128, ..., 4096] and the corresponding aLogN value is [5, 6, ..., 12].

Function Documentation

◆ tpt_rfft_f32()

tpt_status tpt_rfft_f32	(	f32_t *	aOutData,
		f32_t *	aInData,
		size_t	aLogN,
		bool	aIfftFlag
	)

Processing function for the floating-point RFFT/RIFFT.

Source buffer is modified by this function.

Parameters

[out]	aOutData	points to output buffer.
[in]	aInData	points to input buffer (Source buffer is modified by this function.)
[in]	aLogN	The fftLen is 2^aLogN.
[in]	aIfftFlag	flag that selects transform direction value = false: forward transform value = true : inverse transform

Returns

execution status

TPT_MATH_SUCCESS : Operation is successful.
TPT_MATH_ARGUMENT_ERROR : aLogN is not supported.

◆ tpt_rfft_f64()

tpt_status tpt_rfft_f64	(	f64_t *	aOutData,
		f64_t *	aInData,
		size_t	aLogN,
		bool	aIfftFlag
	)

Processing function for the floating-point RFFT/RIFFT.

Source buffer is modified by this function.

Parameters

[out]	aOutData	points to output buffer.
[in]	aInData	points to input buffer (Source buffer is modified by this function.)
[in]	aLogN	The fftLen is 2^aLogN.
[in]	aIfftFlag	flag that selects transform direction value = false: forward transform value = true : inverse transform

Returns

execution status

TPT_MATH_SUCCESS : Operation is successful.
TPT_MATH_ARGUMENT_ERROR : aLogN is not supported.

◆ tpt_rfft_q15()

tpt_status tpt_rfft_q15	(	q15_t *	aOutData,
		q15_t *	aInData,
		size_t	aLogN,
		bool	aIfftFlag
	)

Processing function for the Q15 RFFT/RIFFT.

Source buffer is modified by this function.

Parameters

[out]	aOutData	points to output buffer.
[in]	aInData	points to input buffer (Source buffer is modified by this function.)
[in]	aLogN	The fftLen is 2^aLogN.
[in]	aIfftFlag	flag that selects transform direction value = false: forward transform value = true : inverse transform

Returns

execution status

TPT_MATH_SUCCESS : Operation is successful.
TPT_MATH_ARGUMENT_ERROR : aLogN is not supported.

Input an output formats: Internally input is downscaled for every stage to avoid saturations inside CFFT/CIFFT process. Hence the output format is different for different RFFT sizes. The input and output formats for different RFFT sizes and number of bits to upscale are mentioned in the tables below for RFFT and RIFFT:

Input and Output Formats for Q15 RFFT
aLogN	RFFT Size	Input format	Output format	Number of bits to upscale
4	16	1.15	5.11	4
5	32	1.15	6.10	5
6	64	1.15	7.9	6
7	128	1.15	8.8	7
8	256	1.15	9.7	8
9	512	1.15	10.6	9
10	1024	1.15	11.5	10
......

Input and Output Formats for Q15 RIFFT
aLogN	RFFT Size	Input format	Output format	Number of bits to upscale
4	16	1.15	5.11	0
5	32	1.15	6.10	0
6	64	1.15	7.9	0
7	128	1.15	8.8	0
8	256	1.15	9.7	0
9	512	1.15	10.6	0
10	1024	1.15	11.5	0
......

◆ tpt_rfft_q31()

tpt_status tpt_rfft_q31	(	q31_t *	aOutData,
		q31_t *	aInData,
		size_t	aLogN,
		bool	aIfftFlag
	)

Processing function for the Q31 RFFT/RIFFT.

Source buffer is modified by this function.

Parameters

[out]	aOutData	points to output buffer.
[in]	aInData	points to input buffer (Source buffer is modified by this function.)
[in]	aLogN	The fftLen is 2^aLogN.
[in]	aIfftFlag	flag that selects transform direction value = false: forward transform value = true : inverse transform

Returns

execution status

TPT_MATH_SUCCESS : Operation is successful.
TPT_MATH_ARGUMENT_ERROR : aLogN is not supported.

Input an output formats: Internally input is downscaled for every stage to avoid saturations inside CFFT/CIFFT process. Hence the output format is different for different RFFT sizes. The input and output formats for different RFFT sizes and number of bits to upscale are mentioned in the tables below for RFFT and RIFFT:

Input and Output Formats for Q31 RFFT
aLogN	RFFT Size	Input format	Output format	Number of bits to upscale
4	16	1.31	5.27	4
5	32	1.31	6.26	5
6	64	1.31	7.25	6
7	128	1.31	8.24	7
8	256	1.31	9.23	8
9	512	1.31	10.22	9
10	1024	1.31	11.21	10
......

Input and Output Formats for Q31 RIFFT
aLogN	RFFT Size	Input format	Output format	Number of bits to upscale
4	16	1.31	5.27	0
5	32	1.31	6.26	0
6	64	1.31	7.25	0
7	128	1.31	8.24	0
8	256	1.31	9.23	0
9	512	1.31	10.22	0
10	1024	1.31	11.21	0
......