Question
STM32F072 usb audio
Posted on May 19, 2016 at 04:45
Hi guys,
I new to STM32, was mostly use PIC32 for USB audio application but due to cost decided to switch to STM Now I have STM32F0 discovery board with STM32F072RBT6. I tried to setup USB audio with CubeMX and compile with out no issue. Now I would like to change the Audio Sampling rate to 48KHz instead of 1KHz (code default value). Once change to 48KHz, the code will run into Hard Fault exception. So I take a look into the code and sort of does not understand below part (summarize from various .h and .c)#define USBD_malloc (uint32_t *)USBD_static_malloc
#define USBD_AUDIO_FREQ 22100
#define AUDIO_OUT_PACKET (uint32_t)(((USBD_AUDIO_FREQ * 2 * 2) /1000)) //=4=88bytes
/* Number of sub-packets in the audio transfer buffer. You can modify this value but always make sure
that it is an even number and higher than 3 */
#define AUDIO_OUT_PACKET_NUM 80
/* Total size of the audio transfer buffer = 88*80=7040 bytes!*/
#define AUDIO_TOTAL_BUF_SIZE ((uint32_t)(AUDIO_OUT_PACKET * AUDIO_OUT_PACKET_NUM))
typedef struct
{
uint8_t cmd;
uint8_t data[USB_MAX_EP0_SIZE];
uint8_t len;
uint8_t unit;
}
USBD_AUDIO_ControlTypeDef;
typedef struct
{
__IO uint32_t alt_setting;
uint8_t buffer[AUDIO_TOTAL_BUF_SIZE];
AUDIO_OffsetTypeDef offset;
uint8_t rd_enable;
uint16_t rd_ptr;
uint16_t wr_ptr;
USBD_AUDIO_ControlTypeDef control;
}
////////////////////////////////////////////////////////////////////////////////
// at usbd_conf.c
void *USBD_static_malloc(uint32_t size)
{
//static uint8_t mem[sizeof(USBD_AUDIO_HandleTypeDef)];
/* USER CODE BEGIN 4 */
/**
* To compute the request size you must use the formula:
AUDIO_OUT_PACKET = (USBD_AUDIO_FREQ * AUDIO_BYTES_PER_FRAME * 2) /1000)
AUDIO_TOTAL_BUF_SIZE = AUDIO_OUT_PACKET * AUDIO_OUT_PACKET_NUM with
Number of sub-packets in the audio transfer buffer. You can modify this value but always make sure
that it is an even number and higher than 3
AUDIO_OUT_PACKET_NUM = 80
*/
static uint8_t mem[512]; // fixed sized?
/* USER CODE END 4 */
return mem;
}
////////////////////////////////////////////////////////////////////////////////
// at usbd_audio.c
static uint8_t USBD_AUDIO_Init (USBD_HandleTypeDef *pdev,
uint8_t cfgidx)
{
USBD_AUDIO_HandleTypeDef;
USBD_AUDIO_HandleTypeDef *haudio;
/* Open EP OUT */
USBD_LL_OpenEP(pdev,
AUDIO_OUT_EP,
USBD_EP_TYPE_ISOC,
AUDIO_OUT_PACKET);
/* Allocate Audio structure */
pdev->pClassData = USBD_malloc(sizeof (USBD_AUDIO_HandleTypeDef)); //allocate 512 byte for pClassData which should
hold one packet
if(pdev->pClassData == NULL)
{
return USBD_FAIL;
}
else
{
haudio = (USBD_AUDIO_HandleTypeDef*) pdev->pClassData; //??? pdev->pClassData size if 512 but cast into haudio
which have size AUDIO_TOTAL_BUF_SIZE+77bytes ?? how does this work?
haudio->alt_setting = 0;
haudio->offset = AUDIO_OFFSET_UNKNOWN; //call to this should generate error as it is out of 512?
haudio->wr_ptr = 0;
haudio->rd_ptr = 0;
haudio->rd_enable = 0;
}
...
...
}haudio = (USBD_AUDIO_HandleTypeDef*) pdev->pClassData;
as pdev->pClassData point to 512 bytes space while haudio is pointer toUSBD_AUDIO_HandleTypeDefwhich have size AUDIO_TOTAL_BUF_SIZE+77bytes ??