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Universal Serial BusJordan WeichelJacob LuceroTony Lucchesi

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Outline

http://www.brandsoftheworld.com/search?query_id=3996676&page=1&mtype=&brand_id=22618

• Overview

• Design

• Interface

• Power

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History

• USB 1.0o Full Speed 12 Mbits/s (1.5 MB/s)o Low Speed 1.5 Mbits/s (0.2 MB/s)o 1996o USB 1.1 (1998)

• USB 2.0 oHigh Speed 480 Mbits/s (60 MB/s)o 2000

• USB 3.0 o SuperSpeed 5.0 Gbits/s (625 MB/s)o 2008

http://www.legitreviews.com/article/1150/1/

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USB in Embedded Systems

Self powered

Fast communication

Most reliable way to talk to computers

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USB Wires and Ports

http://commons.wikimedia.org/wiki/File:Types-usb_new.svghttp://i.imgur.com/XwIqQ.jpg

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High-level Design

http://www.l-com.com/images/usb-tutorial-tier-topology.gif

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Endpoints

http://www.mightyape.co.nz/product/Canyon-Full-HD-1080P-Webcam-with-Mic/20977976/images/14450845/

• Endpointso 32 per deviceo (Device_addr, endpoint_num)

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Pipes

• Message pipeso Control

• Short and simple for commands and queries• Stream pipes

o Interrupt• Small bounded latency for quick transfers

o Bulk• Large transfers use remaining bandwidth

o Isochronous• Guaranteed data rate

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Process

http://upload.wikimedia.org/wikipedia/commons/1/1b/USB_pipes_and_endpoints_%28en%29.svgPicture from beyster 1695 p28

• Enumerationo Host assigns each device an addresso Host acquires stream transfer typeso Post enumeration

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USB Protocols

1. Token Packeto Initiatiates communication

2. Data Packeto Contains information / payload

3. Status Packet o Acknowledges transactions o Reports errors

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Transaction

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USB to UART Example

USB VCC(+5v)

Data+Data-

USB GND

Data OutData In

https://www.sparkfun.com/products/650

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Power Pins

http://1.bp.blogspot.com/-6nvzXThVlNU/T9pnBRiSr-I/AAAAAAAAB0o/MFVOHHENVbk/s1600/pin-out-usb3_usb2A.jpg

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Vocabulary

• 100 mA = 1 unit load• Vbus = VCC

o 500 mA max draw from Vbus per deviceo 5 V goal

• Sourceo Powered vs. unpowered

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Power Overview

http://mac-ave.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/3/1/31joqfxn1yl._sl500_aa300_.jpg

1. Low-power2. High-power3. Self-power

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Low-Power Functions

• Max drawo 1 unit load (100 mA)

• Power comes exclusively from Vbus

• Voltageo 4.40 V mino 5.25 V max

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High-Powered Functions

• Max drawo 5 unit loads (500 mA)

• Power comes exclusively from Vbus

• Voltageo 4.40 V mino 5.25 V max

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Self-Powered Functions

• 1 unit load from Vbus

• Rest of the power from external sourceo Requires safety catch to never draw more

than 1 unit load from Vbus

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Power Hiccups

• Suspended deviceso Draw no more than 500 µA

• Vbus unstableo Devices are plugged / unplugged

Transient voltage dips as low as 4.1 VoNeed to design device to handle situation

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Pros and Cons

Universal transfer protocolIncreased reliability and speed of data transfersPre-implemented driversMany devices per hostDedicated hardwareComplex debugging

http://2.bp.blogspot.com/-RSVGM9fJSBQ/Tk-yHnrC7BI/AAAAAAAAAfU/9by6cOS5U1o/s1600/Parallel-Port.jpg

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Questions?

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References

http://www.pcworld.com/article/156494/superspeed_usb.html

http://computer.howstuffworks.com/usb3.htm

http://www.beyondlogic.org/usbnutshell/usb2.shtml

http://www.l-com.com/content/USB-Tutorial.html

http://www.wisegeek.org/what-are-the-advantages-of-usb-30.htm

http://uk.farnell.com/images/en/ede/pdf/usb_dev_mistake.pdf

http://www.usb.org/home

http://www.smxrtos.com/articles/usb_art/waysusb.htm

https://www.sparkfun.com/datasheets/IC/FT232R_v104.pdf