1. ITEC 352 Lecture 32 USB

2. USB (1) Review Exam Intro/review of the bus system

3. USB (1) Objectives Rationale History of USB –Firewire Goal –Electricity to code

4. USB (1) USB What do you know about it? Why is it useful? What alternatives can you think of?

5. USB (1) History Started in 1994 –Several companies participated High / low speed –12 / 1.5 Mbits/s Development continues –USB 2.0 went up to 480 Mbits/s –USB 3.0 is up to 5 Gbit/s

6. USB (1) Similar devices Firewire –Created by a different set of companies Designed for high-end audio/video transfer –Serial not parallel…Why? What differences do you think are made? –Keyboard versus camera Started at 400 Mbit/s (USB 1.0 = Molasses) –Went up to 800 Mbit/s

7. USB (1) Serial versus parallel Getting data into a system Modeling data sent over through –Serial –Parallel What are the advantages and disadvantages of each method Why do you think both types chose serial instead of parallel?

8. USB (1) Topology One to one? Many to one? Many to many? Anyone heard of hubs? Is it synchronous or asynchronous?

9. USB (1) Breakdow n Allows sub-devices –Webcam = Video + Audio –Why is this important? 16 pipes –Two types: Stream and message –Why do think there is a need for two types?

10. USB (1) Transfer modes Isochronous transfers –Guaranteed rate but possible data loss Interrupt transfers –Quick response transfer Bulk transfers –Uses all available bandwidth –No guarantee on timing or latency Control transfers –Tell the device what to do

11. USB (1) Connector Pin Layout (1-4) –Vcc +5V (Why is this important?) –Data- –Data+ –Ground

12. USB (1) Summary USB Introduction / format Next time –Physical mapping –Packets Friday –Code / libraries