Error in USB VCOM CDC example ?

h_bouchard — Tue, 29 Sep 2020 16:32:13 GMT

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

Re: Error in USB VCOM CDC example ?

FelipeGarcia — Fri, 02 Oct 2020 15:38:45 GMT

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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Error in USB VCOM CDC example ?

Re: Error in USB VCOM CDC example ?