How many maximum usb vcom port we can create? Actually i created two vcom port with stm32l452 but not able to create third one. please suggest some help . for vcom port 3 descriptor detail given below.

NMish.2 · ‎2022-09-08

/////////////////////////////////////////////////////

//Add 3 IAD class here // this one is for COM port 3

0x08, // bLength: Interface Descriptor size

0x0B, // bDescriptorType: IAD

0x04, // bFirstInterface

0x03, // bInterfaceCount

0x02, // bFunctionClass: CDC

0x02, // bFunctionSubClass

0x01, // bFunctionProtocol

0x02, // iFunction

/*Interface Descriptor */

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

USB_DESC_TYPE_INTERFACE, /* bDescriptorType: Interface */

/* Interface descriptor type */

0x00+4, /* 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 */

0x00, /* bmCapabilities: D0+D1 */

0x01 + 4 , /* bDataInterface: 1+2 */

/*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+4, /* bMasterInterface: Communication class interface */

0x01+4, /* bSlaveInterface0: Data Class Interface */

/*Endpoint 2 Descriptor*/

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

USB_DESC_TYPE_ENDPOINT, /* bDescriptorType: Endpoint */

CDC_CMD_EP+3, /* bEndpointAddress */

0x03, /* bmAttributes: Interrupt */

LOBYTE(CDC_CMD_PACKET_SIZE), /* wMaxPacketSize: */

HIBYTE(CDC_CMD_PACKET_SIZE),

0x10, /* bInterval: */

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

/*Data class interface descriptor*/

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

USB_DESC_TYPE_INTERFACE, /* bDescriptorType: */

0x01+4, /* 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+4, /* 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+4, /* 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 */

//EP+3---------------------------------------------------------->

/* Open EP IN */

(void)USBD_LL_OpenEP(pdev, CDC_IN_EP+4, USBD_EP_TYPE_BULK,

CDC_DATA_HS_IN_PACKET_SIZE);

pdev->ep_in[(CDC_IN_EP+4) & 0xFU].is_used = 1U;

/* Open EP OUT */

(void)USBD_LL_OpenEP(pdev, CDC_OUT_EP+4, USBD_EP_TYPE_BULK,

CDC_DATA_HS_OUT_PACKET_SIZE);

pdev->ep_out[(CDC_OUT_EP+4) & 0xFU].is_used = 1U;

/* Set bInterval for CDC CMD Endpoint */

pdev->ep_in[(CDC_CMD_EP+4) & 0xFU].bInterval = CDC_HS_BINTERVAL;

//EP+3---------------------------------------------------------------->

/* Open EP IN */

(void)USBD_LL_OpenEP(pdev, CDC_IN_EP+4, USBD_EP_TYPE_BULK,

CDC_DATA_FS_IN_PACKET_SIZE);

pdev->ep_in[(CDC_IN_EP+4) & 0xFU].is_used = 1U;

/* Open EP OUT */

(void)USBD_LL_OpenEP(pdev, CDC_OUT_EP+4, USBD_EP_TYPE_BULK,

CDC_DATA_FS_OUT_PACKET_SIZE);

pdev->ep_out[(CDC_OUT_EP+4) & 0xFU].is_used = 1U;

/* Set bInterval for CMD Endpoint */

pdev->ep_in[(CDC_CMD_EP+4) & 0xFU].bInterval = CDC_FS_BINTERVAL;

(void)USBD_LL_OpenEP(pdev, CDC_CMD_EP+4, USBD_EP_TYPE_INTR, CDC_CMD_PACKET_SIZE);

pdev->ep_in[(CDC_CMD_EP+4) & 0xFU].is_used = 1U;

/* Prepare Out endpoint to receive next packet */

USBD_LL_PrepareReceive(pdev,

CDC_OUT_EP+4,

hcdc->RxBuffer,

CDC_DATA_HS_OUT_PACKET_SIZE);

/* Prepare Out endpoint to receive next packet */

USBD_LL_PrepareReceive(pdev,

CDC_OUT_EP+4,

hcdc->RxBuffer,

CDC_DATA_FS_OUT_PACKET_SIZE);

//-------------------->EP+4

/* Close EP IN */

(void)USBD_LL_CloseEP(pdev, CDC_IN_EP+3);

pdev->ep_in[(CDC_IN_EP+4) & 0xFU].is_used = 0U;

/* Close EP OUT */

(void)USBD_LL_CloseEP(pdev, CDC_OUT_EP+3);

pdev->ep_out[(CDC_OUT_EP+4) & 0xFU].is_used = 0U;

/* Close Command IN EP */

(void)USBD_LL_CloseEP(pdev, CDC_CMD_EP+3);

pdev->ep_in[(CDC_CMD_EP+4) & 0xFU].is_used = 0U;

pdev->ep_in[(CDC_CMD_EP+4) & 0xFU].bInterval = 0U;

Bob S · ‎2022-09-08

IAD bInterfaceCount you have 0x03, should be 0x02. You have 3 endpoints but only 2 interfaces per CDC/VCOM

Endpoint2 descriptor, EP address looks funny ("+3"), maybe that should be +4 like all your other EP increments?

TechGuyMike · ‎2023-03-03

You may need to update the FIFO settings for each additional endpoint you create.

Example: https://github.com/limbongofficial/STM32_Core-Arduino/blob/master/cores/arduino/stm32/usb/usbd_conf.c#L515

Piranha · ‎2023-03-03

https://github.com/hathach/tinyusb/tree/master/examples/device/cdc_dual_ports