stm32 - USB DUAL CDC endpoints for transferring data

Question

I have emulated two VCPs with only one USB Device. I can send data in one VCP that has the following Endpoint Address.

#define CDC_IN_EP    0x81  /* EP1 for data IN */
#define CDC_OUT_EP   0x01  /* EP1 for data OUT */
#define CDC_CMD_EP   0x82  /* EP2 for CDC commands */

I would like to know if it's possible to send data in the other VCP with other Endpoint Address like:

#define CDC_IN_EP3   0x83  /* EP3 for data IN */
#define CDC_OUT_EP3  0x03  /* EP3 for data OUT */
#define CDC_CMD_EP4  0x84  /* EP4 for CDC commands */

My problem is that addresses others than 0x81 don't allow me to send data over the second VCP. I'm using two CDC interfaces Full-Speed. Normally we can use seven endpoints with CDC_FS and that's what I'm trying to do... I have six Endpoints: three for each VCP and the seventh is Endpoint 0 for configuration.

Have I missed something in the Endpoints Configuration or in the Composite Device Descriptors?

/* USB CDC device Configuration Descriptor */
__ALIGN_BEGIN uint8_t USBD_CDC_CfgFSDesc[USB_CDC_CONFIG_DESC_SIZ] __ALIGN_END =
{
    /* Configuration Descriptor */
    0x09,   /* bLength: Configuration Descriptor size */
    USB_DESC_TYPE_CONFIGURATION,  /* bDescriptorType: Configuration */
    USB_CDC_CONFIG_DESC_SIZ,      /* wTotalLength:no of returned bytes */
    0x00,
    0x04,   /* bNumInterfaces: 4 interface */
    0x01,   /* bConfigurationValue: Configuration value */
    0x00,   /* iConfiguration: Index of string descriptor describing the configuration */
    0xC0,   /* bmAttributes: Self powered */
    0x32,   /* MaxPower 100 mA */

    /*---------------------------------------------------------------------------*/

    // IAD0
    0x08,   // bLength: Interface Descriptor size
    0x0B,   // bDescriptorType: IAD
    0x00,   // bFirstInterface
    0x02,   // bInterfaceCount
    0x02,   // bFunctionClass: CDC
    0x02,   // bFunctionSubClass
    0x01,   // bFunctionProtocol
    0x02,   // iFunction

    /* Interface0 Descriptor */
    0x09,   /* bLength: Interface Descriptor size */
    USB_DESC_TYPE_INTERFACE,  /* bDescriptorType: Interface */

    /* Interface descriptor type */
    0x00,   /* bInterfaceNumber: Number of Interface */
    0x00,   /* bAlternateSetting: Alternate setting */
    0x01,   /* bNumEndpoints: One endpoints used */
    0x02,   /* bInterfaceClass: Communication Interface Class */
    0x02,   /* bInterfaceSubClass: Abstract Control Model */
    0x01,   /* bInterfaceProtocol: Common AT commands */
    0x00,   /* iInterface: */

    /* Header Functional Descriptor */
    0x05,   /* bLength: Endpoint Descriptor size */
    0x24,   /* bDescriptorType: CS_INTERFACE */
    0x00,   /* bDescriptorSubtype: Header Func Desc */
    0x10,   /* bcdCDC: spec release number */
    0x01,

    /* Call Management Functional Descriptor */
    0x05,   /* bFunctionLength */
    0x24,   /* bDescriptorType: CS_INTERFACE */
    0x01,   /* bDescriptorSubtype: Call Management Func Desc */
    0x03,   /* bmCapabilities: D0+D1 */
    0x01,   /* bDataInterface: 1 */

    /* ACM Functional Descriptor */
    0x04,   /* bFunctionLength */
    0x24,   /* bDescriptorType: CS_INTERFACE */
    0x02,   /* bDescriptorSubtype: Abstract Control Management desc */
    0x02,   /* bmCapabilities */

    /* Union Functional Descriptor */
    0x05,   /* bFunctionLength */
    0x24,   /* bDescriptorType: CS_INTERFACE */
    0x06,   /* bDescriptorSubtype: Union func desc */
    0x00,   /* bMasterInterface: Communication class interface */
    0x01,   /* bSlaveInterface0: Data Class Interface */


    /* Endpoint 2 Descriptor */
    0x07,                         /* bLength: Endpoint Descriptor size */
    USB_DESC_TYPE_ENDPOINT,       /* bDescriptorType: Endpoint */
    CDC_CMD_EP,                   /* bEndpointAddress */
    0x03,                         /* bmAttributes: Interrupt */
    LOBYTE(CDC_CMD_PACKET_SIZE),  /* wMaxPacketSize: */
    HIBYTE(CDC_CMD_PACKET_SIZE),
    0xFF,                         /* bInterval: */
    /*---------------------------------------------------------------------------*/

    /*Data class interface descriptor*/
    0x09,   /* bLength: Endpoint Descriptor size */
    USB_DESC_TYPE_INTERFACE,  /* bDescriptorType: */
    0x01,   /* bInterfaceNumber: Number of Interface */
    0x00,   /* bAlternateSetting: Alternate setting */
    0x02,   /* bNumEndpoints: Two endpoints used */
    0x0A,   /* bInterfaceClass: CDC */
    0x00,   /* bInterfaceSubClass: */
    0x00,   /* bInterfaceProtocol: */
    0x00,   /* iInterface: */

    /*Endpoint OUT Descriptor*/
    0x07,   /* bLength: Endpoint Descriptor size */
    USB_DESC_TYPE_ENDPOINT,               /* bDescriptorType: Endpoint */
    CDC_OUT_EP,                           /* bEndpointAddress */
    0x02,                                 /* bmAttributes: Bulk */
    LOBYTE(CDC_DATA_FS_MAX_PACKET_SIZE),  /* wMaxPacketSize: */
    HIBYTE(CDC_DATA_FS_MAX_PACKET_SIZE),
    0x00,                                 /* bInterval: ignore for Bulk transfer */

    /*Endpoint IN Descriptor*/
    0x07,   /* bLength: Endpoint Descriptor size */
    USB_DESC_TYPE_ENDPOINT,               /* bDescriptorType: Endpoint */
    CDC_IN_EP,                            /* bEndpointAddress */
    0x02,                                 /* bmAttributes: Bulk */
    LOBYTE(CDC_DATA_FS_MAX_PACKET_SIZE),  /* wMaxPacketSize: */
    HIBYTE(CDC_DATA_FS_MAX_PACKET_SIZE),
    0x00,                                 /* bInterval: ignore for Bulk transfer */

    /*---------------------------------------------------------------------------*/

    // IAD1

    0x08,   // bLength: Interface Descriptor size
    0x0B,   // bDescriptorType: IAD
    0x02,   // bFirstInterface
    0x02,   // bInterfaceCount
    0x02,   // bFunctionClass: CDC
    0x02,   // bFunctionSubClass
    0x01,   // bFunctionProtocol
    0x02,   // iFunction

    /* Interface1 Descriptor */
    0x09,   /* bLength: Interface Descriptor size */
    USB_DESC_TYPE_INTERFACE,  /* bDescriptorType: Interface */
    /* Interface descriptor type */
    0x02,   /* bInterfaceNumber: Number of Interface */
    0x00,   /* bAlternateSetting: Alternate setting */
    0x01,   /* bNumEndpoints: One endpoints used */
    0x02,   /* bInterfaceClass: Communication Interface Class */
    0x02,   /* bInterfaceSubClass: Abstract Control Model */
    0x01,   /* bInterfaceProtocol: Common AT commands */
    0x00,   /* iInterface: */

       /*Header Functional Descriptor*/
    0x05,   /* bLength: Endpoint Descriptor size */
    0x24,   /* bDescriptorType: CS_INTERFACE */
    0x00,   /* bDescriptorSubtype: Header Func Desc */
    0x10,   /* bcdCDC: spec release number */
    0x01,

    /*Call Management Functional Descriptor*/
    0x05,   /* bFunctionLength */
    0x24,   /* bDescriptorType: CS_INTERFACE */
    0x01,   /* bDescriptorSubtype: Call Management Func Desc */
    0x03,   /* bmCapabilities: D0+D1 */
    0x03,   /* bDataInterface: 1 */

    /*ACM Functional Descriptor*/
    0x04,   /* bFunctionLength */
    0x24,   /* bDescriptorType: CS_INTERFACE */
    0x02,   /* bDescriptorSubtype: Abstract Control Management desc */
    0x02,   /* bmCapabilities */

    /*Union Functional Descriptor*/
    0x05,   /* bFunctionLength */
    0x24,   /* bDescriptorType: CS_INTERFACE */
    0x06,   /* bDescriptorSubtype: Union func desc */
    0x02,   /* bMasterInterface: Communication class interface */
    0x03,   /* bSlaveInterface0: Data Class Interface */

    /*Endpoint 2 Descriptor*/
    0x07,                         /* bLength: Endpoint Descriptor size */
    USB_DESC_TYPE_ENDPOINT,       /* bDescriptorType: Endpoint */
    CDC_CMD_EP4,                  /* bEndpointAddress */
    0x03,                         /* bmAttributes: Interrupt */
    LOBYTE(CDC_CMD_PACKET_SIZE),  /* wMaxPacketSize: */
    HIBYTE(CDC_CMD_PACKET_SIZE),
    0xFF,                         /* bInterval: */
    /*---------------------------------------------------------------------------*/

    /*Data class interface descriptor*/
    0x09,   /* bLength: Endpoint Descriptor size */
    USB_DESC_TYPE_INTERFACE,  /* bDescriptorType: */
    0x03,   /* bInterfaceNumber: Number of Interface */
    0x00,   /* bAlternateSetting: Alternate setting */
    0x02,   /* bNumEndpoints: Two endpoints used */
    0x0A,   /* bInterfaceClass: CDC */
    0x00,   /* bInterfaceSubClass: */
    0x00,   /* bInterfaceProtocol: */
    0x00,   /* iInterface: */

    /*Endpoint OUT Descriptor*/
    0x07,   /* bLength: Endpoint Descriptor size */
    USB_DESC_TYPE_ENDPOINT,               /* bDescriptorType: Endpoint */
    CDC_OUT_EP3,                          /* bEndpointAddress */
    0x02,                                 /* bmAttributes: Bulk */
    LOBYTE(CDC_DATA_FS_MAX_PACKET_SIZE),  /* wMaxPacketSize: */
    HIBYTE(CDC_DATA_FS_MAX_PACKET_SIZE),
    0x00,                                 /* bInterval: ignore for Bulk transfer */

    /*Endpoint IN Descriptor*/
    0x07,   /* bLength: Endpoint Descriptor size */
    USB_DESC_TYPE_ENDPOINT,               /* bDescriptorType: Endpoint */
    CDC_IN_EP3,                           /* bEndpointAddress */
    0x02,                                 /* bmAttributes: Bulk */
    LOBYTE(CDC_DATA_FS_MAX_PACKET_SIZE),  /* wMaxPacketSize: */
    HIBYTE(CDC_DATA_FS_MAX_PACKET_SIZE),
    0x00                                  /* bInterval: ignore for Bulk transfer */
};

Answer 1

I had a similar problem with the STM32 USB device library. When you modify or add a new endpoint address in the configuration descriptor, you also have to set the endpoint address in the PMA (packet memory area). You can do that in the USBD_LL_INIT block with the HAL_PCDEx_PMAConfig function:

USBD_StatusTypeDef  USBD_LL_Init (USBD_HandleTypeDef *pdev)
{ 
  /* Init USB_IP */
  /* enable USB power on Pwrctrl CR2 register */
  HAL_PWREx_EnableVddUSB();
  /* Link The driver to the stack */
  hpcd_USB_FS.pData = pdev;
  pdev->pData = &hpcd_USB_FS;

  hpcd_USB_FS.Instance = USB;
  hpcd_USB_FS.Init.dev_endpoints = 8;
  hpcd_USB_FS.Init.speed = PCD_SPEED_FULL;
  hpcd_USB_FS.Init.ep0_mps = DEP0CTL_MPS_8;
  hpcd_USB_FS.Init.phy_itface = PCD_PHY_EMBEDDED;
  hpcd_USB_FS.Init.Sof_enable = DISABLE;
  hpcd_USB_FS.Init.low_power_enable = DISABLE;
  hpcd_USB_FS.Init.lpm_enable = DISABLE;
  hpcd_USB_FS.Init.battery_charging_enable = DISABLE;
  if (HAL_PCD_Init(&hpcd_USB_FS) != HAL_OK)
  {
    Error_Handler();
  }

  HAL_PCDEx_PMAConfig((PCD_HandleTypeDef*)pdev->pData , 0x00 , PCD_SNG_BUF, 0x18);
  HAL_PCDEx_PMAConfig((PCD_HandleTypeDef*)pdev->pData , 0x80 , PCD_SNG_BUF, 0x58);
  HAL_PCDEx_PMAConfig((PCD_HandleTypeDef*)pdev->pData , 0x81 , PCD_SNG_BUF, 0xC0);  
  HAL_PCDEx_PMAConfig((PCD_HandleTypeDef*)pdev->pData , 0x01 , PCD_SNG_BUF, 0x110);
  HAL_PCDEx_PMAConfig((PCD_HandleTypeDef*)pdev->pData , 0x82 , PCD_SNG_BUF, 0x100);  
  return USBD_OK;
}

After that I could use the new endpoints for data transfer.