File content as of revision 0:78e37c7585e6:

#include "mbed.h"
#include "stm32h747i_discovery.h"
#include "stm32h747i_discovery_audio.h"

extern "C" {

    /* Audio frequency */
#define AUDIO_FREQUENCY            BSP_AUDIO_FREQUENCY_16K
#define AUDIO_IN_PDM_BUFFER_SIZE  (uint32_t)(128*AUDIO_FREQUENCY/16000*DEFAULT_AUDIO_IN_CHANNEL_NBR)

    /* Size of the recorder buffer */
#define RECORD_BUFFER_SIZE        4096

    /* Define record Buf at D3SRAM @0x38000000 since the BDMA for SAI4 use only this memory */
#if defined (TOOLCHAIN_IAR)  /* IAR */
    /* No need to update linker script */
#pragma location=0x38000000
    uint16_t recordPDMBuf[AUDIO_IN_PDM_BUFFER_SIZE];
#else  /* GCC_ARM and ARM */
    /* Linker scripts need to be updated to add RAM_D3 section */
    ALIGN_32BYTES(uint16_t recordPDMBuf[AUDIO_IN_PDM_BUFFER_SIZE]) __attribute__((section(".RAM_D3")));
#endif

    uint16_t playbackBuf[RECORD_BUFFER_SIZE * 2];

    /* Pointer to record_data */
    uint32_t playbackPtr;

    extern SAI_HandleTypeDef haudio_out_sai;
    extern SAI_HandleTypeDef haudio_in_sai;


    /**
      * @brief  This function handles DMA2 Stream 1 interrupt request.
      * @param  None
      * @retval None
      */
    void AUDIO_OUT_SAIx_DMAx_IRQHandler(void)
    /* DMA2_Stream1_IRQHandler redefinition in BSP_DISCO_H747I/STM32H747I-Discovery/stm32h747i_discovery_audio.h */
    {
        HAL_DMA_IRQHandler(haudio_out_sai.hdmatx);
    }


    /**
      * @brief  This function handles BDMA Channel 1 for SAI_PDM interrupt request.
      * @param  None
      * @retval None
      */
    void AUDIO_IN_SAI_PDMx_DMAx_IRQHandler(void)
    /* BDMA_Channel1_IRQHandler redefinition in BSP_DISCO_H747I/STM32H747I-Discovery/stm32h747i_discovery_audio.h */
    {
        HAL_DMA_IRQHandler(haudio_in_sai.hdmarx);
    }


    /**
      * @brief Calculates the remaining file size and new position of the pointer.
      * @param  None
      * @retval None
      */
    void BSP_AUDIO_IN_TransferComplete_CallBack(void)
    /* weak empty function in BSP_DISCO_H747I/STM32H747I-Discovery/stm32h747i_discovery_audio.c */
    {
        if (BSP_AUDIO_IN_GetInterface() == AUDIO_IN_INTERFACE_PDM) {
            /* Invalidate Data Cache to get the updated content of the SRAM*/
            SCB_InvalidateDCache_by_Addr((uint32_t *)&recordPDMBuf[AUDIO_IN_PDM_BUFFER_SIZE / 2], AUDIO_IN_PDM_BUFFER_SIZE * 2);

            BSP_AUDIO_IN_PDMToPCM((uint16_t *)&recordPDMBuf[AUDIO_IN_PDM_BUFFER_SIZE / 2], &playbackBuf[playbackPtr]);

            /* Clean Data Cache to update the content of the SRAM */
            SCB_CleanDCache_by_Addr((uint32_t *)&playbackBuf[playbackPtr], AUDIO_IN_PDM_BUFFER_SIZE / 4);

            playbackPtr += AUDIO_IN_PDM_BUFFER_SIZE / 4 / 2;
            if (playbackPtr >= RECORD_BUFFER_SIZE) {
                playbackPtr = 0;
            }
        }
    }


    /**
      * @brief  Manages the DMA Half Transfer complete interrupt.
      * @param  None
      * @retval None
      */
    void BSP_AUDIO_IN_HalfTransfer_CallBack(void)
    /* weak empty function in BSP_DISCO_H747I/STM32H747I-Discovery/stm32h747i_discovery_audio.c */
    {
        if (BSP_AUDIO_IN_GetInterface() == AUDIO_IN_INTERFACE_PDM) {
            /* Invalidate Data Cache to get the updated content of the SRAM*/
            SCB_InvalidateDCache_by_Addr((uint32_t *)&recordPDMBuf[0], AUDIO_IN_PDM_BUFFER_SIZE * 2);

            BSP_AUDIO_IN_PDMToPCM((uint16_t *)&recordPDMBuf[0], &playbackBuf[playbackPtr]);

            /* Clean Data Cache to update the content of the SRAM */
            SCB_CleanDCache_by_Addr((uint32_t *)&playbackBuf[playbackPtr], AUDIO_IN_PDM_BUFFER_SIZE / 4);

            playbackPtr += AUDIO_IN_PDM_BUFFER_SIZE / 4 / 2;
            if (playbackPtr >= RECORD_BUFFER_SIZE) {
                playbackPtr = 0;
            }
        }
    }


    /**
      * @brief  Audio IN Error callback function
      * @param  None
      * @retval None
      */
    void BSP_AUDIO_IN_Error_CallBack(void)
    /* weak empty function in BSP_DISCO_H747I/STM32H747I-Discovery/stm32h747i_discovery_audio.c */
    {
        MBED_ASSERT(0);
    }

} // extern C


int main()
{
    printf("\n\nAUDIO LOOPBACK EXAMPLE WITH AUDIO PDM FOR DISCO-H747I\n");

    /* Set audio input interface */
    BSP_AUDIO_IN_SelectInterface(AUDIO_IN_INTERFACE_PDM);

    /* Initialize audio IN at REC_FREQ*/
    if (BSP_AUDIO_IN_InitEx(INPUT_DEVICE_DIGITAL_MIC, AUDIO_FREQUENCY, DEFAULT_AUDIO_IN_BIT_RESOLUTION, DEFAULT_AUDIO_IN_CHANNEL_NBR) != AUDIO_OK) {
        /* Record Error */
        MBED_ASSERT(0);
    }

    /* Initialize audio OUT at REC_FREQ*/
    if (BSP_AUDIO_OUT_Init(OUTPUT_DEVICE_HEADPHONE, 50, AUDIO_FREQUENCY) != AUDIO_OK) {
        /* Record Error */
        MBED_ASSERT(0);
    }

    /* Set audio slot */
    BSP_AUDIO_OUT_SetAudioFrameSlot(CODEC_AUDIOFRAME_SLOT_02);

    /* Start the record */
    BSP_AUDIO_IN_Record((uint16_t *)recordPDMBuf, AUDIO_IN_PDM_BUFFER_SIZE);

    wait_us(1000); // 1 ms

    /* Start audio output */
    BSP_AUDIO_OUT_Play((uint16_t *)playbackBuf, RECORD_BUFFER_SIZE * 2);
}