Understanding USB

Universal Serial Bus is more than a way to connect your keyboard to your computer. USB is being used to control a multitude of devices such as scanners, printers, interactive white boards, camera mounts, automated lifts and blinds and other devices. USB also transfers files and is common in sharing music, video and data. What are the limitations of USB? What are the speeds and how do you know whether your USB connection will work to the desired level? Participants in this program will leave with a full understanding of the genesis and evolution of the USB standard, best installation practices and challenges and the future of data connections. Along with audio and video, USB is fast becoming one of the most important A/V project connections. Don't be left behind.

Transcript

1. PRODUCT LINE Technology For Interactive & AV Applications Understanding USB Joseph Cornwall, CTS-D
2. PRODUCT LINE Our Agenda • USB History and Types • USB and Time • USB and Tiers • USB and Power • USB and Future Technology
3. PRODUCT LINE Universal Serial Bus • USB Was Designed To Standardize The Connection Of Computer Peripherals – Replaced Serial And Parallel Ports – Eliminated The Need For Separate Power Supplies For Devices • USB Was Born Of The Need For Plug-And-Play Technology – Allows For “Hot Swapping” – Connect Up To 127 “Devices” • USB Is Bi-Directional – Allows The Flow Of Information Into AND Out Of A Computer (Host)
4. PRODUCT LINE USB History USB was designed to offer plug and play compatibility • Replace parallel and serial ports • 1.0 released 1996 • 1.1 released 1998 • 2.0 released 2000 • 3.0 released 2008 • 3.1 released 2013
5. PRODUCT LINE USB 1.1, 2.0 And 3.0 1.1 1.5 Mbit/s “Low Speed” Connection For Low Data Rate Devices  “Human Interface Devices” 12 Mbit/s “Full Speed”  Mass Storage Device  Imaging Device 2.0 • 480 Mbit/s “Hi Speed” Devices – 60 MB/S – Sufficient For Sound Playback – Supports Compressed Video Capability 3.0 5 Gbit/s “Superspeed” – 625 MB/s, More Than 10 Times Faster Than USB 2.0 – USB 3.0 Is “Green” And Uses About One-third The Power Of USB 2.0
6. PRODUCT LINE Comparison Of USB 2.0 And 3.0 Connections USB 2.0 “A” and “B” USB 3.0 “A” and “B”
7. PRODUCT LINE Examination Of USB Bus Speeds
8. PRODUCT LINE USB Topology • USB Leverages An Asymmetrical Star Topology –Host, Downstream Ports, Peripherals • USB Host (Computer) May Implement Multiple Host Controllers –Each Host Controller May Provide One Or More USB Ports –Up To 127 Devices, Including Hub Devices If Present, May Be Connected To A Single Host Controller –Root Hub Is Built Into The Host Controller
9. PRODUCT LINE 7 Tiers Of Communication • Tiers Describe How Ports, Hubs And Devices (Also Called "Functions") Are Connected • The Main USB Host Always Occupies Tier-1 • Both Hubs And Extenders Occupy Tiers 2 Through 6 • Devices (Functions) Are Always Tier 7
10. PRODUCT LINE Round Robin USB Device Enumeration USB Communicates In A “Round Robin” Fashion Reset Signal Sent To Device Data Rate Determined Device Assigned Unique 7-bit Address Device Drivers Loaded Host Controller Polls The Bus For Traffic Transaction Translators Convert Between High-speed USB 2.0 Buses And Full And Low Speed Buses
11. PRODUCT LINE Time Is Of The Essence • USB Is A Half-Duplex System – 3.0 and 3.1 are Full Duplex • USB Operates Within Rigid Time Constraints – Hubs And Devices Must Respond To The Host Within A Tightly Defined Time Frame • Defined Response Times In USB Limit Cable Lengths Due To Finite Propagation Velocities In The Cable Structure – 15 Feet In Full-Speed Or High-Speed Mode – For Longer Connections We Must Use USB Extenders
12. PRODUCT LINE USB Logical Channels USB Communication Is Based On Logical Channels (Pipes) Connection From The Host To A Logical Entity (Endpoint) Device May Have As Many As 32 Endpoints 16 Out, 16 In 2 Types Of Pipes Stream Pipe (Unidirectional) For Isochronous, Interrupt Or Bulk Message Pipe (Bi-directional) For Control Data Flow
13. PRODUCT LINE USB Transfer Types • Isochronous transfers at some guaranteed data but with possible data loss • Interrupt transfers guarantee quick responses (bounded latency) • Bulk transfers are for large sporadic transfers using all remaining available bandwidth, but with no guarantees on bandwidth or latency • Control transfers are used for short, simple commands or device status response
14. PRODUCT LINE USB Devices All USB logical devices present the same basic interface to the host, and any device that can transmit or receive data is known as a “function”  A mug warmer, for example, doesn’t transmit data and is not a function A “function” is always recognized as tier 7 of the USB pyramid  No devices connect after a function Devices may be composite or compound  Composite = 2 functions with a “virtual” hub  Compound = 2 functions with an actual hub
15. PRODUCT LINE Compound And Composite A USB compound device appears to the host as a hub with one or more non-removable USB devices embedded  Each function appears as a discrete device attached to a hub  To the USB system, a compound device occupies two tiers Compound devices are relatively unusual, while composite devices are very common
16. PRODUCT LINE Understanding Hubs Hubs consist of 3 components Repeater - connects and releases functions Controller - communicates with the host Transaction translator – controls speeds The hub must always reside between tiers 2 and 6 If there is more than one USB port on the computer, there is an internal hub connected to the root hub Hubs are self-powered or bus powered
17. PRODUCT LINE Hubs Are Wiring Concentrators Hubs enable multiple attachment characteristics Attachment points are called “ports” Each downstream port can be individually enabled and attached at any speed
18. PRODUCT LINE Example Of 7-Port USB Hub In Tier Occupied Port 1 Port 2 Port 3 Port 4 Tier Occupied In Port 4 Port 5 Port 6 Port 7
19. PRODUCT LINE EXTENDING THE USB SYSTEM “Civilization advances by extending the number of important operations which we can perform without thinking about them.” - Alfred North Whitehead
20. PRODUCT LINE Understanding USB Extender Systems USB’s inherent time limitations allow for cable length of no more than 5 meters  USB 3.0 has no limits per se, but in practical applications 3.0 performance can only be achieved to about 10ft Hubs regenerate the signal and are repeaters Almost all USB extenders are seen by the host as a hub
21. PRODUCT LINE USB SuperBooster Converts USB signal to a proprietary signal  Each manufacturer may use their own technology Some USB superbooster systems do not have to occupy a tier  Bus powered systems typically occupy a tier Some self-powered superboosters use a NAK (not acknowledged) communication protocol to “get around” system latency  Data packet not accepted; please retransmit  Occurs during “handshake”
22. PRODUCT LINE USB POWER “All power corrupts, but we need the electricity.” - Unknown
23. PRODUCT LINE Power In The USB Environment USB specifies a 5 V (+/-5%) power supply Power is delivered in quanta of unit loads A single unit load is 100 mA Low-power device draw 1 unit load High-power device draws up to the maximum number of unit loads permitted (5 unit loads)
24. PRODUCT LINE Charging Ports – Charging downstream port (CDP) • Supports data transfer • May not exceed 900 mA during high-speed data transfer – Dedicated charging port (DCP) • No data support • There is no upper limit for the rated current of a charging downstream port, as long as the connector can handle the current
25. PRODUCT LINE PRACTICAL USB SYSTEM ANALYSIS “The height of cleverness is to be able to conceal it.” - Francois de La Rochefoucauld
26. PRODUCT LINE USB System Example
27. PRODUCT LINE Analyzing The USB Network Using device manager you can see devices, connections and power demands For a detailed “tree” view USB protocol analyzer USBDeview is a free download Linux or windows
28. PRODUCT LINE USBDeview Screen Cap A free software download that allows analysis of USB connections
29. PRODUCT LINE USB COMPETITORS “Competition is a painful thing, but it produces great results.” - Jerry Flint
30. PRODUCT LINE Firewire Firewire networks use a tree topology  Any device can communicate with any other node at any time  Any capable node can control the network in Firewire USB uses 5 V power. Firewire uses 12 V Firewire can (in theory) supply up to 60 watts of power Designed for high performance  Particularly suited for time-sensitive applications such as A/V
31. PRODUCT LINE Thunderbolt • Based on the mini DisplayPort connector – Originally conceived as an optical technology, thunderbolt switched to electrical connections to reduce costs – Supplies up to 10W of power to connected devices • Interoperable with DisplayPort 1.2 devices – When connected to a DP++ compatible device, the Thunderbolt port can provide a native DP++ signal
32. PRODUCT LINE IN CONCLUSION… “A conclusion is the place where you got tired of thinking.” − Harold Fricklestein 32
33. PRODUCT LINE In Conclusion… • USB allows up to 127 “functions” (devices) to be connected to a host via 7 tiers of connectivity • USB provides power in quanta of unit loads – 1 unit load = 100 mA – Maximum of 5 unit loads • USB networks may contain “hidden” internal hubs • USB extenders “look like” hubs – Place power demands on bus- powered – Occupy a tier of communication
34. PRODUCT LINE Questions?