File content as of revision 26:d67b45687c92:

/**
  ******************************************************************************
  * @file    OpenPDMFilter.h
  * @author  CL
  * @version V1.0.0
  * @date    9-September-2015
  * @brief   Header file for Open PDM audio software decoding Library.   
  *          This Library is used to decode and reconstruct the audio signal
  *          produced by ST MEMS microphone (MP45Dxxx, MP34Dxxx). 
 ******************************************************************************
  * @attention
  *
  * <h2><center>&copy; COPYRIGHT 2013 STMicroelectronics</center></h2>
  *
  * Licensed under MCD-ST Image SW License Agreement V2, (the "License");
  * You may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *        http://www.st.com/software_license_agreement_image_v2
  *
  * Unless required by applicable law or agreed to in writing, software 
  * distributed under the License is distributed on an "AS IS" BASIS, 
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
  ******************************************************************************
  */

/* Define to prevent recursive inclusion -------------------------------------*/

#ifndef __OPENPDMFILTER_H
#define __OPENPDMFILTER_H

#ifdef __cplusplus
  extern "C" {
#endif


/* Includes ------------------------------------------------------------------*/

#include <stdint.h>


/* Definitions ---------------------------------------------------------------*/

/*
 * Enable to use a Look-Up Table to improve performances while using more FLASH
 * and RAM memory.
 * Note: Without Look-Up Table up to stereo@16KHz configuration is supported.
 */
#define USE_LUT

#define SINCN            3
#define DECIMATION_MAX 128
#define FILTER_GAIN     16

#define HTONS(A) ((((uint16_t)(A) & 0xff00) >> 8) | \
                 (((uint16_t)(A) & 0x00ff) << 8))
#define RoundDiv(a, b)    (((a)>0)?(((a)+(b)/2)/(b)):(((a)-(b)/2)/(b)))
#define SaturaLH(N, L, H) (((N)<(L))?(L):(((N)>(H))?(H):(N)))


/* Types ---------------------------------------------------------------------*/

typedef struct {
  /* Public */
  float LP_HZ;
  float HP_HZ;
  uint16_t Fs;
  uint8_t In_MicChannels;
  uint8_t Out_MicChannels;
  uint8_t Decimation;
  uint8_t MaxVolume;
  /* Private */
  uint32_t Coef[SINCN];
  uint16_t FilterLen;
  int64_t OldOut, OldIn, OldZ;
  uint16_t LP_ALFA;
  uint16_t HP_ALFA;
  uint16_t bit[5];
  uint16_t byte;
} TPDMFilter_InitStruct;


/* Exported functions ------------------------------------------------------- */

void Open_PDM_Filter_Init(TPDMFilter_InitStruct *init_struct);
void Open_PDM_Filter_64(uint8_t* data, uint16_t* data_out, uint16_t mic_gain, TPDMFilter_InitStruct *init_struct);
void Open_PDM_Filter_128(uint8_t* data, uint16_t* data_out, uint16_t mic_gain, TPDMFilter_InitStruct *init_struct);

#ifdef __cplusplus
}
#endif

#endif // __OPENPDMFILTER_H

/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/