# Release Notes for PDM audio software decoding Library
Author: MCD Application Team

Copyright 2015 STMicroelectronics

The PDM audio software decoding Library is an optimized software implementation for PDM signal decoding and audio signal reconstruction when connecting an ST MEMS microphone (MP45Dxxx, MP34Dxxx) with an STM32 microcontroller. It can directly take the Pulse Density Modulated (PDM) data output from the microphone and convert it to 16-bit pulse-code modulation (PCM) format.
This Library includes one header file pdm_filter.h and binary/object codes running on all STM32 devices. The naming format is libPDMFilter_CMx_C.a/.lib, where:

- CMx: CortexMx core class (CM0, CM3, CM4 and CM7)
- C: compiler (IAR, Keil and GCC)

For more information about this Library, please refer to the document "AN3998 PDM audio software decoding on STM32 microcontrollers" available for download from STMicroelectronics website at www.st.com.

## Update History

### V2.1.0 / 31-March-2015

Main Changes

- Add Binaries for CortexM7 (CM7) core
- PDM_Filter_128_MSB() and PDM_Filter_128_LSB() functions: enhance volume setting, it was lower than expected
- PDM_Filter_64_MSB() function: fix issue when using more than 2 microphones

### V2.0.1 / 17-December-2013

Main Changes

- In HTONS() macro, change u16 type by uint16_t

### V2.0.0 / 07-August-2013

Main Changes

- Update Library binary name format
- Add Library version optimized for CM0, CM3 and CM4F cores
- Add functions for decimation factor 128

### V1.1.2 / 17-April-2012

Main Changes

- All source files: license disclaimer text update and add link to the License file on ST Internet.

### V1.1.1 / 30-December-2011

Main Changes

- PDM Library moved from Utilities\STM32F4-Discovery to Utilities\STM32_Audio\Addons\PDM folder
- Add new license agreement "MCD-ST Image SW License Agreement V2.pdf"

### V1.1.0 / 28-October-2011

Main Changes

- Add PDM audio software decoding Library drivers, used to decode and reconstruct the audio signal produced by MP45DT02 MEMS microphone from STMicroelectronics. For more details about this Library, please refer to document "PDM audio software decoding on STM32 microcontrollers (AN3998)".
- stm32f4_discovery_audio_codec.c/.h: update to use DMA instead of Interrupt in I2S communication with the external codec.

### V1.0.0 / 19-September-2011

Main Changes

- First official version of the STM32F4-Discovery Board Drivers

## License

Licensed under MCD-ST Image SW License Agreement V2, (the "License"); You may not use this package 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.

For complete documentation on STM32 Microcontrollers visit www.st.com/STM32