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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

Basic Communication Model

The host and the device have distinct layers, as shown in the picture below. Ultimately, the communication occurs on the physical USB wire. However, there are logical host-device interfaces between each horizontal layer.

The major host layers are the:

  • Client describing the software entities responsible for interacting directly with USB devices.
  • USB System managing data transfers between the host and USB devices.
  • USB Bus Interface handling interactions of the electrical and protocol layers and actually transmits the packets.

Host layers have the role to:

  • Detect the attachment and removal of USB devices.
  • Manage USB control flows between the host and USB devices.
  • Manage data flows between the host and USB devices.
  • Collect status and activity statistics.
  • Control the electrical interface.

USB Communication Model

The major device layers are the:

  • Function providing a new capability, for instance, a mouse, a keyboard, an mp3-player, or an ISDN interface.
  • USB Device managing data transfers between the host and USB devices.
  • USB Bus Interface handling interactions of the electrical and protocol layers and actually transmits the packets.
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