Improved doxygen documentation for FFTs.

Documentation/Doxygen/src/mainpage.md

@@ -163,6 +163,21 @@ All algorithms are compared with a double precision reference and the different
 
 As consequence, the small differences that may exists between the different architecture implementations should be too small to have any practical consequences.
 
+Also, when targetting Helium or Neon, some functions have  different APIs.
+
+### Different API for Helium
+* Biquad F32 and F16 : A different init function must be used
+* FIR F32, F16, Q31, Q15 and Q7 : Coefficient array must be padded with zeros
+
+### Different API for Neon
+* Biquad F32 initialization : An additional function must be used for initialization
+* MFCC F32, F16, Q31 and Q15 : Additional temporary buffer required for the functions
+* CFFT F32, F16, Q31 and Q15 : Additional temporary buffer required for the functions
+* RFFT F32, F16, Q31 and Q15 : Additional temporary buffer required for the functions. Different arguments for the init function of Q31 and Q15 RFFT
+
+For CFFT and RFFT, a new Neon specific initialization function is available to be able to use longer FFTs.
+
+For CFFT, this new Neon specific initialization allows to use FFT lengths with factor of 3 and 5 in the length (but must still be a multiple of 4 length).
 
 
 ## License {#license}

Include/dsp/transform_functions.h

@@ -86,6 +86,10 @@ extern "C"
  *  On Neon, there is another possibility. You can use arm_cfft_init_dynamic_q15. This function will allocate a buffer at runtime and compute at runtime all the tables that are required for a specific FFT size. This initialization is also supported by RFFT.
  *  The computation to initialize all the tables can take lot of cycles
  *  (since several cos and sin must be computed)
+ *  
+ *  With this new Neon specific initialization you can use longer lengths.
+ *  With CFFT, you can also use lengths containing radix 3 and/or 5 (but
+ *  the length must still be a multiple of 4).
  */
 
 

Ne10/CMSIS_NE10_fft_init.c

@@ -376,6 +376,10 @@ static ne10_fft_cpx_float32_t* ne10_fft_generate_twiddles_transposed_float32 (
  *            memory must be released when no more used.
  *            This function can be used with FFT lengths
  *            longer than the ones supported on Cortex-M
+ *            
+ *            With this function, FFT lengths can also contain
+ *            factor 3 and 5 (but must be multiple of 4)
+ *            
  */
 arm_cfft_instance_f32 *arm_cfft_init_dynamic_f32(uint32_t fftLen)
 {
@@ -517,6 +521,9 @@ arm_cfft_instance_f32 *arm_cfft_init_dynamic_f32(uint32_t fftLen)
  *            memory must be released when no more used.
  *            This function can be used with FFT lengths
  *            longer than the ones supported on Cortex-M
+ *            
+ *            With this function, FFT lengths can also contain
+ *            factor 3 and 5 (but must be multiple of 4)
  */
 arm_cfft_instance_q31 *arm_cfft_init_dynamic_q31(uint32_t fftLen)
 {
@@ -613,6 +620,9 @@ arm_cfft_instance_q31 *arm_cfft_init_dynamic_q31(uint32_t fftLen)
  *            memory must be released when no more used.
  *            This function can be used with FFT lengths
  *            longer than the ones supported on Cortex-M
+ *            
+ *            With this function, FFT lengths can also contain
+ *            factor 3 and 5 (but must be multiple of 4)
  */
 arm_cfft_instance_q15 *arm_cfft_init_dynamic_q15(uint32_t fftLen)
 {
@@ -834,6 +844,9 @@ static ne10_fft_cpx_float16_t* ne10_fft_generate_twiddles_transposed_float16 (
  *            memory must be released when no more used.
  *            This function can be used with FFT lengths
  *            longer than the ones supported on Cortex-M
+ *            
+ *            With this function, FFT lengths can also contain
+ *            factor 3 and 5 (but must be multiple of 4)
  */
 arm_cfft_instance_f16 *arm_cfft_init_dynamic_f16(uint32_t fftLen)
 {
@@ -962,6 +975,7 @@ arm_cfft_instance_f16 *arm_cfft_init_dynamic_f16(uint32_t fftLen)
  *            memory must be released when no more used.
  *            This function can be used with RFFT lengths
  *            longer than the ones supported on Cortex-M
+ *            
  */
 arm_rfft_fast_instance_f16 *arm_rfft_fast_init_dynamic_f16 (uint32_t nfft)
 {
@@ -1140,6 +1154,7 @@ arm_rfft_fast_instance_f16 *arm_rfft_fast_init_dynamic_f16 (uint32_t nfft)
  *            memory must be released when no more used.
  *            This function can be used with RFFT lengths
  *            longer than the ones supported on Cortex-M
+ *            
  */
 arm_rfft_fast_instance_f32 *arm_rfft_fast_init_dynamic_f32 (uint32_t nfft)
 {
@@ -1317,6 +1332,7 @@ arm_rfft_fast_instance_f32 *arm_rfft_fast_init_dynamic_f32 (uint32_t nfft)
  *            memory must be released when no more used.
  *            This function can be used with RFFT lengths
  *            longer than the ones supported on Cortex-M
+ *            
  */
   arm_rfft_instance_q31 *arm_rfft_init_dynamic_q31(uint32_t nfft)
   {
@@ -1428,6 +1444,7 @@ arm_rfft_fast_instance_f32 *arm_rfft_fast_init_dynamic_f32 (uint32_t nfft)
  *            memory must be released when no more used.
  *            This function can be used with RFFT lengths
  *            longer than the ones supported on Cortex-M
+   *            
    */
   arm_rfft_instance_q15 *arm_rfft_init_dynamic_q15(uint32_t nfft)
   {