Usb Connection With The Hid Class Driver

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Usb Connection With The Hid Class Driver

  1. 1. USB Communication/Configuration Overview How does communication between a USB device and a PC work? How does a USB device initiate contact with a PC?
  2. 2. How does communication between a USB device and a PC work? Logical Communication Flow Endpoint 1 Endpoint 2 Endpoint N Endpoints Have 4 Transfer Types: Control Transfer – For sending commands Interrupt Transfer – Host must poll this EP Isochronous Transfer – Time sensitive Info Bulk Transfer – For large data bursts Buffer 1 Buffer 2 Buffer N Data is sent to memory buffers which will be processed by the software application Interface 1 Software Application Interfaces : grouping of the endpoints into a functional group performing a single feature of the device. For example: Keyboard,Mouse,Camera,Scanner,DVD drive Operating System
  3. 3. How does communication between a USB device and a PC work? Renesas H8S /2215 Device c PC OS Firmware Hardware Firmware Hardware Firmware Firmware Interface Description Grouping of endpoints performing a single feature of the device Relationship Collection of Endpoints Various transfer types: Control,Interrupt, Isochronous,Bulk Data Transfer Per Endpoint Serial Interface Engine USB Bus Interface Physical/Signal/Packet Connectivity Data USB Driver Software Application Interprets data based on Interfaces Buffered Data USB Bus Interface Serial Interface Engine Physical/Signal/Packet Connectivity USB Cable Data Host Controller Driver Device’s configuration, status, and control information. Endpoint 0: Control Pipe Manages System Devices . Data USB System Software Host Controller UHCI OHCI EHCI Data
  4. 4. How does a USB device initiate contact with a PC? Configuration Descriptor How the Device is setup Device Address Device Descriptor Represents the device 1 USB System Software Endpoint 0 Control Pipe Device’s configuration, status, and control information. Wait 100ms for USB Stabilization 2 3 PC gives Device an Address 4 PC requests Device Descriptor 5 PC requests Configuration Descriptor 6 Windows asks for driver for the device. Driver is then located and installed. 7
  5. 5. How does a USB device initiate contact with a PC? USB System Software Endpoint 0 1 Wait 100ms for USB Stabilization 2 This descriptor contains the Interface and Endpoint descriptor 5 Configuration Descriptor How the Device is setup PC gives Device an Address Device Address 4 3 Device Descriptor Represents the device PC requests Device Descriptor 6 Windows asks for driver for the device. Driver is then located and installed. 7

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