Post on 29-Mar-2015
1
Universal Serial BusJordan WeichelJacob LuceroTony Lucchesi
2
Outline
http://www.brandsoftheworld.com/search?query_id=3996676&page=1&mtype=&brand_id=22618
• Overview
• Design
• Interface
• Power
3
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/
4
USB in Embedded Systems
Self powered
Fast communication
Most reliable way to talk to computers
5
USB Wires and Ports
http://commons.wikimedia.org/wiki/File:Types-usb_new.svghttp://i.imgur.com/XwIqQ.jpg
6
High-level Design
http://www.l-com.com/images/usb-tutorial-tier-topology.gif
7
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)
8
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
9
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
10
USB Protocols
1. Token Packeto Initiatiates communication
2. Data Packeto Contains information / payload
3. Status Packet o Acknowledges transactions o Reports errors
11
Transaction
12
USB to UART Example
USB VCC(+5v)
Data+Data-
USB GND
Data OutData In
https://www.sparkfun.com/products/650
13
Power Pins
http://1.bp.blogspot.com/-6nvzXThVlNU/T9pnBRiSr-I/AAAAAAAAB0o/MFVOHHENVbk/s1600/pin-out-usb3_usb2A.jpg
14
Vocabulary
• 100 mA = 1 unit load• Vbus = VCC
o 500 mA max draw from Vbus per deviceo 5 V goal
• Sourceo Powered vs. unpowered
15
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
16
Low-Power Functions
• Max drawo 1 unit load (100 mA)
• Power comes exclusively from Vbus
• Voltageo 4.40 V mino 5.25 V max
17
High-Powered Functions
• Max drawo 5 unit loads (500 mA)
• Power comes exclusively from Vbus
• Voltageo 4.40 V mino 5.25 V max
18
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
19
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
20
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
21
Questions?
22
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