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DESCRIPTION
USB development
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USB USB Communication/Configuration Communication/Configuration
OverviewOverview
How does communication between a How does communication between a USB device and a PC work?USB device and a PC work?
How does a USB device initiate contact with a PC?
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
How does communication between a USB device How does communication between a USB device and a PC work? and a PC work?
Logical Communication Flow
Buffer 1 Buffer 2 Buffer NData 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
Renesas H8S /2215 Device
c
PC
OS
Firmware
Hardware
Firmware
Hardware
Firmware
Firmware
How does communication between a USB device How does communication between a USB device and a PC work?and a PC work?
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 ConnectivityUSB Cable
Data
Host Controller Driver
Device’s configuration, status, and control information.
Endpoint 0: Control Pipe
Manages System
Devices.
Data USB System Software
Host ControllerUHCIOHCIEHCI
Data
Configuration Descriptor
How the Device is setup
Device Address
Device Descriptor
Represents the device
How does a USB device initiate contact with a PC?How does a USB device initiate contact with a PC?
1
USB System Software
Endpoint 0 Control PipeDevice’s configuration, status, and control information.
Wait 100ms for USB Stabilization
2
3
PC gives Device an Address4
PC requests Device Descriptor
5PC requests Configuration Descriptor
6 Windows asks for driver for the device.
Driver is then located and installed.
7
USB System Software
Endpoint 0
How does a USB device initiate contact with a PC?How does a USB device initiate contact with a PC?1
Wait 100ms for USB Stabilization
2 This descriptor contains the Interface and Endpoint descriptor
5Configuration Descriptor
How the Device is setup
PC gives Device an Address
Device Address
43
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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