stm32f207vc usb bulk tramission , only 64bytes can be sent?

[easylwl]

Posted on April 10, 2013 at 09:55

I use stm32f207  USB device examples  VCP deom .I change the USB CDC device Configuration Descriptor like this

/*Configuration Descriptor*/

  0x09,   /* bLength: Configuration Descriptor size */

  USB_CONFIGURATION_DESCRIPTOR_TYPE,      /* bDescriptorType: Configuration */

  USB_CDC_CONFIG_DESC_SIZ,                /* wTotalLength:no of returned bytes */

  0x00,

  0x01,   /* bNumInterfaces: 1 interface */

  0x01,   /* bConfigurationValue: Configuration value */

  0x00,   /* iConfiguration: Index of string descriptor describing the configuration */

  0xC0,   /* bmAttributes: self powered */

  250,   /* MaxPower 2 mA */

  

  /*Data class interface descriptor*/

  0x09,   /* bLength: Endpoint Descriptor size */

  USB_INTERFACE_DESCRIPTOR_TYPE,  /* bDescriptorType: */

  0x00,   /* bInterfaceNumber: Number of Interface */

  0x00,   /* bAlternateSetting: Alternate setting */

  0x02,   /* bNumEndpoints: Two endpoints used */

  0xff,   /* bInterfaceClass: USER */

  0x00,   /* bInterfaceSubClass: */

  0x00,   /* bInterfaceProtocol: */

  0x00,   /* iInterface: */

 

  //18

 

  /*Endpoint OUT Descriptor*/

  0x07,   /* bLength: Endpoint Descriptor size */

  USB_ENDPOINT_DESCRIPTOR_TYPE,      /* bDescriptorType: Endpoint */

  0x03,                        /* bEndpointAddress */

  0x02,                              /* bmAttributes: Bulk */

  0x40,  /* wMaxPacketSize: */

  0,

  0,                              /* bInterval: ignore for Bulk transfer */

  //25

  /*Endpoint IN Descriptor*/

  0x07,   /* bLength: Endpoint Descriptor size */

  USB_ENDPOINT_DESCRIPTOR_TYPE,      /* bDescriptorType: Endpoint */

  0x82,                         /* bEndpointAddress */

  0x02,                              /* bmAttributes: Bulk */

  0x40,  /* wMaxPacketSize: */

  0,

  0                               /* bInterval: ignore for Bulk transfer */

  //32

and I send function :

uint16_t VCP_DataTx (uint8_t* Buf, uint32_t Len)

{

uint8_t i;

for (i=0;i<64;i++)      //this number must be

multiple 

of  64 ,anyother number wil not be send out.

        {

        APP_Rx_Buffer[APP_Rx_ptr_in] = g_ucaHeartbeat;

        APP_Rx_ptr_in++;

         

          /* To avoid buffer overflow */

          if(APP_Rx_ptr_in == APP_RX_DATA_SIZE)

          {

            APP_Rx_ptr_in = 0;

          }  

        }

return USBD_OK;

}

#stm32f207-cdc-virtualcom-usb

[dthedens23]

Posted on April 10, 2013 at 19:11

Full speed bulk endpoint limit is 64 bytes.  For performance, you want to send full packets.

if you need more granularity, consider another type of end point.

[easylwl]

Posted on April 15, 2013 at 11:13

But when I send 8 bytes ,by calling DCD_EP_Tx(len=8) ,it can not be sent successful?

what wrong with me?