Reasons for USB-UART Component Enumeration Failure – KBA90556

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What are the possible reasons for the USB-UART component failing to enumerate?



The USB_UART component fails to enumerate if there is a mismatch between the VDDD supplied on the board and VDDD voltage settings in the PSoC® Creator™. You must ensure that these values match. You can check the value for your project in PSoC Creator as shown in the figure below.


Figure 1. VDDD Setting in the .cydwr Tab

In addition, you must ensure that in the USBFS_Start(uint8 device, uint8 mode) and USBFS_InitComponent(uint8 device, uint8 mode) APIs, the value to the argument uint8 mode matches the VDDD used in the design. USBFS_Start() API activates the component in specific voltage mode and USBFS_InitComponent() API This function initializes the component’s global variables and initiates communication with the host by pull-up D+ line. Please refer the USBUART component datasheet for more details of the APIs.