File content as of revision 4:bf9ab5993081:

#include "mbed.h"
#include "AUDIO_DISCO_F746NG.h"
#include "SDRAM_DISCO_F746NG.h"

AUDIO_DISCO_F746NG audio;
// audio IN_OUT buffer is stored in the SDRAM, SDRAM needs to be initialized and FMC enabled
SDRAM_DISCO_F746NG sdram;

DigitalOut led_green(LED1);
DigitalOut led_red(LED2);
Serial pc(USBTX, USBRX);

typedef enum
{
    BUFFER_OFFSET_NONE = 0,
    BUFFER_OFFSET_HALF = 1,
    BUFFER_OFFSET_FULL = 2,
}BUFFER_StateTypeDef;

#define AUDIO_BLOCK_SIZE   ((uint32_t)512)
#define AUDIO_BUFFER_IN     SDRAM_DEVICE_ADDR     /* In SDRAM */
#define AUDIO_BUFFER_OUT   (SDRAM_DEVICE_ADDR + (AUDIO_BLOCK_SIZE * 2)) /* In SDRAM */
__IO uint32_t  audio_rec_buffer_state = BUFFER_OFFSET_NONE;
static uint8_t SetSysClock_PLL_HSE_200MHz();
int main()
{
    SetSysClock_PLL_HSE_200MHz();
    pc.baud(9600);

    pc.printf("\n\nAUDIO LOOPBACK EXAMPLE START:\n");
    led_red = 0;
  
    pc.printf("\nAUDIO RECORD INIT OK\n");
    pc.printf("Microphones sound streamed to headphones\n");
    
    /* Initialize SDRAM buffers */
    memset((uint16_t*)AUDIO_BUFFER_IN, 0, AUDIO_BLOCK_SIZE*2);
    memset((uint16_t*)AUDIO_BUFFER_OUT, 0, AUDIO_BLOCK_SIZE*2);
    audio_rec_buffer_state = BUFFER_OFFSET_NONE;

    /* Start Recording */
    audio.IN_Record((uint16_t*)AUDIO_BUFFER_IN, AUDIO_BLOCK_SIZE);

    /* Start Playback */
    audio.OUT_SetAudioFrameSlot(CODEC_AUDIOFRAME_SLOT_02);
    audio.OUT_Play((uint16_t*)AUDIO_BUFFER_OUT, AUDIO_BLOCK_SIZE * 2);

  
    while (1) {
        /* Wait end of half block recording */
        while(audio_rec_buffer_state == BUFFER_OFFSET_HALF) {
        }
        audio_rec_buffer_state = BUFFER_OFFSET_NONE;
        /* Copy recorded 1st half block */
        memcpy((uint16_t *)(AUDIO_BUFFER_OUT), (uint16_t *)(AUDIO_BUFFER_IN), AUDIO_BLOCK_SIZE);
        /* Wait end of one block recording */
        while(audio_rec_buffer_state == BUFFER_OFFSET_FULL) {
        }
        audio_rec_buffer_state = BUFFER_OFFSET_NONE;
        /* Copy recorded 2nd half block */
        memcpy((uint16_t *)(AUDIO_BUFFER_OUT + (AUDIO_BLOCK_SIZE)), (uint16_t *)(AUDIO_BUFFER_IN + (AUDIO_BLOCK_SIZE)), AUDIO_BLOCK_SIZE);
    }
}
/*-------------------------------------------------------------------------------------
       Callbacks implementation:
           the callbacks API are defined __weak in the stm32746g_discovery_audio.c file
           and their implementation should be done in the user code if they are needed.
           Below some examples of callback implementations.
  -------------------------------------------------------------------------------------*/
/**
  * @brief Manages the DMA Transfer complete interrupt.
  * @param None
  * @retval None
  */
void BSP_AUDIO_IN_TransferComplete_CallBack(void)
{
  audio_rec_buffer_state = BUFFER_OFFSET_FULL;
  return;
}

/**
  * @brief  Manages the DMA Half Transfer complete interrupt.
  * @param  None
  * @retval None
  */
void BSP_AUDIO_IN_HalfTransfer_CallBack(void)
{
  audio_rec_buffer_state = BUFFER_OFFSET_HALF;
  return;
}

static uint8_t SetSysClock_PLL_HSE_200MHz()
{
  RCC_ClkInitTypeDef RCC_ClkInitStruct;
  RCC_OscInitTypeDef RCC_OscInitStruct;

  // Enable power clock  
  __PWR_CLK_ENABLE();
  
  // Enable HSE oscillator and activate PLL with HSE as source
  RCC_OscInitStruct.OscillatorType      = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState            = RCC_HSE_ON; /* External xtal on OSC_IN/OSC_OUT */

  // Warning: this configuration is for a 25 MHz xtal clock only
  RCC_OscInitStruct.PLL.PLLState        = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource       = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM            = 25;            // VCO input clock = 1 MHz (25 MHz / 25)
  RCC_OscInitStruct.PLL.PLLN            = 400;           // VCO output clock = 400 MHz (1 MHz * 400)
  RCC_OscInitStruct.PLL.PLLP            = RCC_PLLP_DIV2; // PLLCLK = 200 MHz (400 MHz / 2)
  RCC_OscInitStruct.PLL.PLLQ            = 8;             // USB clock = 50 MHz (400 MHz / 8)
  
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    return 0; // FAIL
  }

  // Activate the OverDrive to reach the 216 MHz Frequency
  if (HAL_PWREx_EnableOverDrive() != HAL_OK)
  {
    return 0; // FAIL
  }
  
  // Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 clocks dividers
  RCC_ClkInitStruct.ClockType      = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);
  RCC_ClkInitStruct.SYSCLKSource   = RCC_SYSCLKSOURCE_PLLCLK; // 200 MHz
  RCC_ClkInitStruct.AHBCLKDivider  = RCC_SYSCLK_DIV1;         // 200 MHz
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;           //  50 MHz
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;           // 100 MHz
  
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_7) != HAL_OK)
  {
    return 0; // FAIL
  }
  HAL_RCC_MCOConfig(RCC_MCO1, RCC_MCO1SOURCE_HSE, RCC_MCODIV_4);
  return 1; // OK
}