Error in USB VCOM CDC example ?

[h_bouchard]

Hello all,

I have a question concerning the USB virtual com example. In the following code:

usb_status_t USB_DeviceCdcVcomCallback(class_handle_t handle, uint32_t event, void *param)
{
    usb_status_t error = kStatus_USB_Error;
    uint32_t len;
    uint8_t *uartBitmap;
    usb_cdc_acm_info_t *acmInfo = &s_usbCdcAcmInfo;
    usb_device_cdc_acm_request_param_struct_t *acmReqParam;
    usb_device_endpoint_callback_message_struct_t *epCbParam;
    acmReqParam = (usb_device_cdc_acm_request_param_struct_t *)param;
    epCbParam   = (usb_device_endpoint_callback_message_struct_t *)param;
    switch (event)
    {
        case kUSB_DeviceCdcEventSendResponse:
        {
            if ((epCbParam->length != 0) && (!(epCbParam->length % g_UsbDeviceCdcVcomDicEndpoints[0].maxPacketSize)))
            {
                /* If the last packet is the size of endpoint, then send also zero-ended packet,
                 ** meaning that we want to inform the host that we do not have any additional
                 ** data, so it can flush the output.
                 */
                error = USB_DeviceCdcAcmSend(handle, USB_CDC_VCOM_BULK_IN_ENDPOINT, NULL, 0);
            }
            else if ((1 == s_cdcVcom.attach) && (1 == s_cdcVcom.startTransactions))
            {
                if ((epCbParam->buffer != NULL) || ((epCbParam->buffer == NULL) && (epCbParam->length == 0)))
                {
                    /* User: add your own code for send complete event */
                    /* Schedule buffer for next receive event */
                    error = USB_DeviceCdcAcmRecv(handle, USB_CDC_VCOM_BULK_OUT_ENDPOINT, s_currRecvBuf,
                                                 g_UsbDeviceCdcVcomDicEndpoints[0].maxPacketSize);
#if defined(FSL_FEATURE_USB_KHCI_KEEP_ALIVE_ENABLED) && (FSL_FEATURE_USB_KHCI_KEEP_ALIVE_ENABLED > 0U) && \
    defined(USB_DEVICE_CONFIG_KEEP_ALIVE_MODE) && (USB_DEVICE_CONFIG_KEEP_ALIVE_MODE > 0U) &&             \
    defined(FSL_FEATURE_USB_KHCI_USB_RAM) && (FSL_FEATURE_USB_KHCI_USB_RAM > 0U)
                    s_waitForDataReceive = 1;
                    USB0->INTEN &= ~USB_INTEN_SOFTOKEN_MASK;
#endif
                }
            }
        }
        break;
        case kUSB_DeviceCdcEventRecvResponse:
        {
            if ((1 == s_cdcVcom.attach) && (1 == s_cdcVcom.startTransactions))
            {
                s_recvSize = epCbParam->length;

#if defined(FSL_FEATURE_USB_KHCI_KEEP_ALIVE_ENABLED) && (FSL_FEATURE_USB_KHCI_KEEP_ALIVE_ENABLED > 0U) && \
    defined(USB_DEVICE_CONFIG_KEEP_ALIVE_MODE) && (USB_DEVICE_CONFIG_KEEP_ALIVE_MODE > 0U) &&             \
    defined(FSL_FEATURE_USB_KHCI_USB_RAM) && (FSL_FEATURE_USB_KHCI_USB_RAM > 0U)
                s_waitForDataReceive = 0;
                USB0->INTEN |= USB_INTEN_SOFTOKEN_MASK;
#endif
                if (!s_recvSize)
                {
                    /* Schedule buffer for next receive event */
                    error = USB_DeviceCdcAcmRecv(handle, USB_CDC_VCOM_BULK_OUT_ENDPOINT, s_currRecvBuf,
                                                 g_UsbDeviceCdcVcomDicEndpoints[0].maxPacketSize);
#if defined(FSL_FEATURE_USB_KHCI_KEEP_ALIVE_ENABLED) && (FSL_FEATURE_USB_KHCI_KEEP_ALIVE_ENABLED > 0U) && \
    defined(USB_DEVICE_CONFIG_KEEP_ALIVE_MODE) && (USB_DEVICE_CONFIG_KEEP_ALIVE_MODE > 0U) &&             \
    defined(FSL_FEATURE_USB_KHCI_USB_RAM) && (FSL_FEATURE_USB_KHCI_USB_RAM > 0U)
                    s_waitForDataReceive = 1;
                    USB0->INTEN &= ~USB_INTEN_SOFTOKEN_MASK;
#endif
                }
            }
        }

For cases kUSB_DeviceCdcEventSendResponse and kUSB_DeviceCdcEventRecvResponse, in the USB_DeviceCdcAcmRecv function call, endpoint index 0 is used to get max packet size  (g_UsbDeviceCdcVcomDicEndpoints[0].maxPacketSize). However, this call reference BULK_OUT endpoint which is define at index 1 of g_UsbDeviceCdcVcomDicEndpoints variable:

/* Define endpoint for data class */
usb_device_endpoint_struct_t g_UsbDeviceCdcVcomDicEndpoints[USB_CDC_VCOM_ENDPOINT_DIC_COUNT] = {
    {
        USB_CDC_VCOM_BULK_IN_ENDPOINT | (USB_IN << 7U), USB_ENDPOINT_BULK, FS_CDC_VCOM_BULK_IN_PACKET_SIZE, 0U,
    },
    {
        USB_CDC_VCOM_BULK_OUT_ENDPOINT | (USB_OUT << 7U), USB_ENDPOINT_BULK, FS_CDC_VCOM_BULK_OUT_PACKET_SIZE, 0U,
    }};

Shouldn't it be index 1 (g_UsbDeviceCdcVcomDicEndpoints[1].maxPacketSize) passed in parameter to the function ? In this case it won't change anything as both max packet size for BULK_IN and BULK_OUT have the same value but I just want to clarify my understanding of USB stack.

Thanks

Hugio

[FelipeGarcia · Accepted solution]

Hi Hugio,

I checked this and I agree with you. Even though there is no much consequence as this is an error scenario, the index should be 1. Thanks for pointing this out for us.

Have a great day,

Felipe

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