Keil Logo

Technical Support

On-Line Manuals

RL-ARM User's Guide (MDK v4)

RL-RTX RL-FlashFS RL-TCPnet RL-CAN RL-USB RL-USB for USB Device Applications RL-USB Device Library RL-USB Device Features RL-USB Device Software Stack RL-USB Device Functions RL-USB Device Source Files RL-USB Device Configuration Audio Device (ADC) Options Communication Device (CDC) - ACM Options Human Interface Device (HID) Options Mass Storage Device (MSC) Options Create USB Device Applications Create ADC Applications Create CDC ACM Applications Create HID Applications Create MSC Applications Create Composite Applications Test USB Device Applications Compliance Tests Test HID Client Application RL-USB for USB Host Applications RL-USB Host Library RL-USB Host Features RL-USB Host Software Stack RL-USB Host Functions RL-USB Host Source Files RL-USB Host Configuration Host Controller Driver Selection Host Controller Driver Configuration Host Class Driver Selection Create USB Host Applications Create USB Host HID Applications HID_Kbd Example Create USB Host MSC Applications Create USB Host Class Driver RL-USB Host Constants and Structures Error constants Speed constants Transaction Packet Type constants Transaction Error Type constants USB Request Block structure (USBH_URB) Endpoint structure (USBH_EP) Driver Capabilites structure (USBH_HCI_CAP) Device Class Instance structure (USBH_DCI) Host Controller Instance structure (USBH_HCI) Host Controller Driver structure (USBH_HCD) USB Concepts USB Transfer Rates USB Network Basic Communication Model USB Protocol Control Transfer Interrupt Transfer Isochronous Transfer Bulk Transfer Descriptors Device Configuration Device Descriptor Configuration Descriptor Interface Descriptor Endpoint Descriptor Device Qualifier Descriptor Example Programs Library Reference Appendix

Descriptors

USB devices report their attributes using descriptors. A descriptor is a data structure with a defined format. Each descriptor begins with a byte-wide field containing the total number of bytes in the descriptor followed by a byte-wide field identifying the descriptor type.

This is not a complete list of all the possible descriptors a USB host can request. However, as a minimum, the USB device must provide the device descriptor, configuration descriptor, interface descriptor, and three endpoint descriptors.

The USB Host sends setup requests as soon as the device has joined the USB network. The device will be instructed to select a configuration and an interface to match the needs of the application running on the USB Host. Once a configuration and an interface have been selected, the device must service the active endpoints to exchange data with the USB Host.

  Arm logo
Important information

This site uses cookies to store information on your computer. By continuing to use our site, you consent to our cookies.

Change Settings

Privacy Policy Update

Arm’s Privacy Policy has been updated. By continuing to use our site, you consent to Arm’s Privacy Policy. Please review our Privacy Policy to learn more about our collection, use and transfers
of your data.