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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

Device Configuration

When a USB device is attached to or removed from the USB, the host uses a process known as bus enumeration to identify and manage the device.

The data requested by the host are stored in a hierarchy of descriptors. Descriptors are arrays of data, which fully describe the device.

The minimum and required number of descriptors are:

  • One Device Descriptor.
  • One Configuration Descriptor.
  • One Interface Descriptor.
  • Three Endpoint Descriptors (one control, one IN, and one OUT).

Device Configuration

Complex devices have multiple interfaces. Each interface can have a number of endpoints representing a functional unit. For example, a voice-over-IP phone might have:

  • One audio class interface with 2 endpoints for transferring audio data in each direction.
  • One HID interface with a single IN interrupt endpoint for a built-in keypad.
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