usb fundamentals and applications for digital signal processing
Download
Skip this Video
Download Presentation
USB Fundamentals and Applications for Digital Signal Processing

Loading in 2 Seconds...

play fullscreen
1 / 81

USB Fundamentals and Applications for Digital Signal Processing - PowerPoint PPT Presentation


  • 204 Views
  • Uploaded on

USB Fundamentals and Applications for Digital Signal Processing. Greg Burk J. Gordon Electronic Design [email protected] 7/30/2004. Agenda. USB Specifications USB Basics Components Onion introduction Signaling Packets Transfers Requests Operating System Interface

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'USB Fundamentals and Applications for Digital Signal Processing' - demitrius


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
usb fundamentals and applications for digital signal processing

USB Fundamentals and Applications for Digital Signal Processing

Greg Burk

J. Gordon Electronic Design

[email protected]

7/30/2004

agenda
Agenda
  • USB Specifications
  • USB Basics
  • Components
  • Onion introduction
    • Signaling
    • Packets
    • Transfers
    • Requests
    • Operating System Interface
  • Considerations for DSP Applications
  • USB Resources
usb specifications
USB Specifications
  • USB 1.0 – The original spec, superseded quickly by USB 1.1
  • USB 1.1 – Minor enhancements to the USB 1.0 spec, supported Low and Full speed devices
  • USB 2.0 – The Current Standard, added “high speed’ to USB 1.1
  • USB OTG – USB On-the-Go, a supplement to the USB 2.0 spec that added a form of device to device communications.
  • WUSB – Wireless USB, a work in progress -- not a standard yet
usb 2 0 in a nutshell
USB 2.0 in a Nutshell
  • Runs 40X faster than USB 1.1
    • Low speed: 1.5Mb/s
    • Full speed: 12Mb/s
    • High speed: 480Mb/s
  • Fully supports existing USB devices
    • Forward compatible—plug existing 1.1 devices into new 2.0 hosts
    • Backward compatible—plug new 2.0 devices into existing 1.1 hosts
  • Uses the same cables as USB 1.1
usb on the go usb otg
USB On-the-Go (USB OTG)
  • Connect two ‘peripherals’ together
    • PC is not required (but still supported)
  • Allow peripherals to wake up hosts
  • Allow two devices to exchange the host role
  • New OTG devices can tap into the existing 900 million USB devices
usb otg example applications source beeman www usbonthego com
Host

Peripheral

Applications

PC

Cell Phone

Camera

MP3 player

Synchronize phone list, meetings

Upload pictures

Download songs

Cell Phone

Cell Phone

Printer

Camera

Exchange Contact info

Print call info

Upload pictures to web

Camera

Camera

Cell Phone

Printer

Exchange pictures

Upload pictures to web

Print pictures

MP3 player

MP3 player

Exchange songs

USB OTG Example ApplicationsSource:Beeman: www.usbonthego.com
usb otg details
USB OTG Details
  • Defines a new connector and cable
    • “Mini AB” receptacle
    • Mini-A to Mini-B cable
    • Cable establishes the default host
      • A-Device is the default host
  • Dual-role USB devices:
    • Are sometimes a peripheral, sometimes a host
    • Must use the new AB connector
    • Provide limited host capability
      • Targeted peripheral list
    • Operate at full speed (high speed optional)
wireless usb wusb
Wireless USB (WUSB)
  • Specification currently under development (expected release early 2005)
  • Key players are: Intel, Microsoft, HP, NEC, Phillips Semiconductors, Agere Systems, and Samsung Electronics
  • Based on Ultra-wideband (UWB) standard
  • Supposed to support USB 2.0 bandwidth (480 Mb/s) at distances of up to 10 meters
  • Projected Feature Set:
    • Compatibility with USB 2.0 Standard
    • Security at same level as wired USB
    • Connections up to 127 WUSB device
  • For More info see: http://www.intel.com/labs/wusb/
  • (This is NOT the same as Cypress Semiconductors Wireless USB)
usb basics1
USB Basics
  • USB is a Master/Slave Polled Bus (PC is the “Master”, Devices are the “Slaves”)
  • USB has a “tiered star” architecture that can USB can support up to 126 devices
    • 7-bit address = 128 – root hub – reserved addr 0 for enumeration
  • USB is “Hot Pluggable”
  • USB connections can provide both data and power to the devices
usb is not simple
USB is not Simple
  • Outside, it is simple
  • The “rich user experience” requires some inner complexity
  • Even though it replaces serial and parallel ports, it’s not a drop-in replacement
  • It’s electrically simple, but a whole protocol layer is added
usb projects can require a significant code development effort
USB Projects Can Require a Significant Code Development Effort
  • Device side
    • USB houskeeping firmware
    • Application firmware
  • Host side
    • Driver (maybe)
    • Application software
components of usb systems
Components of USB Systems
  • USB Host Controllers
  • USB Hubs
  • USB Cables
  • USB Peripheral Devices
usb host controllers
USB Host Controllers
  • Reside in PC on motherboard or add-in card
  • Are the “master” device on the USB bus
  • Host Controller has integral “Root Hub”
  • Host Controller Interfaces:
      • Universal Host Controller Interface (UHCI)
      • Open Host Controller Interface (OHCI)
      • Enhanced Host Controller Interface (EHCI)
usb cables
USB Cables
  • Transport both Data and Power
  • Four wires: Vbus, GND, D+, D–
  • Cables are 5 meters MAX
  • Two connector types, “A” and “B”
    • Prevents illegal topologies
    • “A” connectors are the ones that goes to the PC or Hub, “B” connectors goes to the device) (OTG adds Miny A and Mini B connectors)
  • Cables can be either “captive” (like mice) or detachable
  • Cables can be unshielded (Low speed devices) or shielded (Full Speed and High Speed devices)
  • USB extension cables are ILLEGAL
usb hubs
USB Hubs
  • A hub provides additional connection points (ports) for devices
  • Hubs can be:
      • Self-Powered (<= 500ma to each device)
      • Bus-Powered (<= 100mA to each device)
  • Hubs contain most of the “magic” and differences between USB 1.1 and USB 2.0
usb devices
USB Devices
  • Devices can be:
      • Self-Powered
        • External Power Source (i.e. wall wart)
        • Batteries
      • Bus-Powered
        • Low Power Bus Powered (<= 100mA)
        • High Power Bus Powered >100mA, <=500mA)
  • Devices are “self describing”
      • Devices return data (USB descriptors) to host to indicate its capabilities, configurations, and how the device is able to communicate
compound and composite devices
Compound and Composite Devices
  • Composite Device
    • Multiple interfaces, independently controlled
      • Each interface can have a different driver
  • Compound Device
    • Collection of separate functions, each with a USB address, connected to an internal hub
    • Example: Keyboard & Trackball in same package
usb is a polled bus
USB is a Polled BUS
  • The Host (PC) initiates all transfers
  • Devices respond to host requests
  • Direction: OUT is host-to-device
  • Direction: IN is device-to-host
  • USB is NOT peer-to-peer (not even in USB OTG)
usb topology
USB Topology

PC

PC

USB

USB

USB

USB

Hub

Device

Device

Device

USB

USB

USB

USB

Device

Device

“Tiered Star”

usb transfer speeds
USB Transfer Speeds
  • USB 1.1:
    • Low speed is 1.5Mb/s
    • Full speed is 12Mb/s
  • USB 2.0
    • Low speed is 1.5Mb/s
    • Full speed is 12Mb/s
    • High speed is 480 Mb/s

There is a VERY common misconception that say a device is USB 2.0 compliant that it means that it is High Speed device. It does NOT!

endpoints
Endpoints
  • USB Spec: “a source or sink of data”
    • A Control Transfer Type endpoint is bi-directional
    • Others are uni-directional
  • Four address bits plus a direction bit selects between up to 32 buffers (FIFOs)
  • Different USB chips support
    • Various numbers of endpoints
    • Various buffer sizes
  • Each device must have 1 Control Type Endpoint (Commonly referred to as Endpoint 0 or the Default Endpoint)
pipes
Pipes
  • An abstraction used by the USB spec used to indicate that 2 endpoints are joined (one in the PC Host and the other in the device).
      • CONTROL pipe is bi-directional
      • Others are uni-directional
usb descriptors
USB Descriptors
  • Device Descriptors
      • Contains the VID/PID/DID/Serial Number
  • Configuration Descriptors
  • Interface Descriptors
  • Endpoint Descriptors
  • String Descriptors
  • Device Qualifier Descriptors (USB 2.0)
  • Other Speed Configuration Descriptors (USB 2.0)
  • USB “Classes” can add other class specific Descriptors
the usb onion
OS Interface

Requests

Transfers

Packets

Signaling

The USB Onion
usb signaling
USB Signaling
  • USB utilizes differential signaling on the D+ and D- lines.
  • Data is encoded in “non-return to zero with bit stuffing”
      • Bit stuffing is used to ensure enough transitions for the clock recovery circuitry.
  • Most designs use silicon that incorporates an integral Serial Interface Engine (SIE) so you don’t have to worry about the decoding yourself.
  • PCB layout of D= and D- requires care (especially on High Speed devices).
the sie serial interface engine
The SIE(Serial Interface Engine)

Serial

D+

Interface

Bytes

Engine

D+

(SIE)

USB

Transceiver

usb packets
USB Packets
  • USB data travels in packets
  • Identified by “Packet ID” (PID)
  • Token packet tells what’s coming
  • Data packets deliver bytes
  • Handshake packets report success or otherwise
packet ids pids
Packet IDs (PIDS)
  • Token Packets
      • IN, OUT, SOF, SETUP
  • Data Packets
      • DATA0, DATA1 (USB LS/FS)
      • DATA2, MDATA (USB HS)
  • Handshake Packets
      • ACK, NAK, STALL (USB LS/FS)
      • NYET (USB HS)
handshaking packets
Handshaking Packets
  • Used to ensure correct data delivery on Control, Bulk and Interrupt Transfers
  • ACK – Received with out Error
  • NAK – Device Busy, has no data
  • Stall – Unsupported Request, Request Failed
  • No Response – Request not received or corrupt, will be retried up to 3 times.
usb transfer types
USB Transfer Types
  • Bulk
    • Guaranteed accuracy, but delivery time is variable
    • Best for “bursty” data
  • Isochronous
    • Guaranteed delivery time, but accuracy is not guaranteed
  • Control
    • Enumeration and device control
  • Interrupt
    • Predictable polling time
usb transfers
USB Transfers
  • USB Transfers Occur in 1ms Frames (USB 2.0 adds 125 uS Microframes)
  • Host sends “SOF” (Start Of Frame) token every 1ms
  • Host schedules packets inside frames.
anatomy of a usb frame
Anatomy of a USB Frame

1 msec frame

  • 12MHz = 1.5MB/s or 1500 bytes/ms
  • Isochronous/Interrupt traffic have guaranteed bandwidth
  • Control traffic is “best-effort”
  • Bulk uses what is left
  • Actual scheduling order depends on host controller
    • UHCI, OHCI

...

SOF

SOF

Video

Mouse

Control

Printer

Audio

Printer

Isochronous

Interrupt

Control

Bulk

packet sizes
Transfer Type

Packet Size

USB 1.1

USB 2.0

Control

Bulk

Interrupt

Isochronous

8, 16, 32, 64

8, 16, 32, 64

1–64

1023

64

512

1024

1024

Packet Sizes
bulk in transfer a
Bulk IN Transfer (a)

H

D

H

H

D

H

D

D

C

C

A

E

C

A

E

C

A

A

A

A

R

R

Payload

Payload

I

D

N

R

I

D

N

R

T

C

T

C

C

C

N

D

D

C

N

D

D

C

Data

Data

A

K

A

K

1

1

R

P

5

R

P

5

1

0

6

6

Token Packet

Token Packet

Data Packet

Data Packet

H/S Pkt

H/S Pkt

good

good—note the data toggle

bulk in transfer b
Bulk IN Transfer (b)

H

D

H

H

D

D

H

H

D

D

C

C

A

E

C

A

E

C

A

E

C

A

A

N

A

A

R

R

Payload

Payload

I

D

N

R

I

D

N

R

I

D

N

R

T

C

A

T

C

C

C

N

D

D

C

N

D

D

C

Data

Data

N

D

D

C

A

K

K

A

K

1

1

R

P

5

R

P

5

R

P

5

1

0

6

6

Token Packet

Token Packet

Data Packet

Data Packet

H/S Pkt

H/S Pkt

Token Packet

H/S Pkt

good

not ready

good

bulk in transfer c
Bulk IN Transfer (c)

H

D

(H)

H

D

H

D

D

C

C

A

E

C

A

E

C

A

A

A

R

R

Payload

Payload

I

D

N

R

I

D

N

R

T

T

C

C

C

N

D

D

C

N

D

D

C

Data

Data

A

A

K

1

1

R

P

5

R

P

5

1

1

6

6

Token Packet

Token Packet

Data Packet

Data Packet

H/S Pkt

host sees error; no response

good—note same data and data toggle

bulk in transfer d
Bulk IN Transfer (d)

H

D

H

(D)

S

A

E

C

A

E

C

T

I

D

N

R

I

D

N

R

A

N

D

D

C

N

D

D

C

L

R

P

5

R

P

5

L

Token Packet

Token Packet

H/S Pkt

device has a problem

device detects token error

or does not respond

bulk out transfer a
Bulk OUT Transfer (a)

H

H

D

H

H

D

D

D

C

C

A

E

C

A

E

C

O

O

A

A

A

A

R

R

Payload

Payload

D

N

R

D

N

R

U

U

T

C

T

C

C

C

D

D

C

D

D

C

Data

Data

T

T

A

K

A

K

1

1

R

P

5

R

P

5

0

1

6

6

Token Packet

Token Packet

Data Packet

Data Packet

H/S Pkt

H/S Pkt

good

good—note the data toggle

bulk out transfer b
Bulk OUT Transfer (b)

H

H

D

H

D

H

D

H

H

D

D

D

C

C

C

A

E

C

A

E

C

A

E

C

O

A

A

A

N

A

A

R

O

R

O

R

Payload

Payload

Payload

D

N

R

D

N

R

D

N

R

U

T

C

T

A

T

C

C

U

C

U

C

D

D

C

Data

Data

Data

D

D

C

D

D

C

T

A

K

A

K

A

K

1

T

1

T

1

R

P

5

R

P

5

R

P

5

1

0

0

6

6

6

Token Packet

Data Packet

Data Packet

Data Packet

H/S Pkt

Token Packet

H/S Pkt

Token Packet

H/S Pkt

good

good

device not ready for data

host sends data anyway

bulk out transfer c
Bulk OUT Transfer (c)

H

H

(D)

H

H

D

D

D

C

C

A

E

C

A

E

C

O

O

A

A

A

R

R

Payload

Payload

D

N

R

D

N

R

U

U

T

T

C

C

C

D

D

C

D

D

C

Data

Data

T

T

A

A

K

1

1

R

P

5

R

P

5

1

1

6

6

Token Packet

Token Packet

Data Packet

Data Packet

H/S Pkt

good

device sees error; no response

bulk out transfer d
Bulk OUT Transfer (d)

(D)

H

H

H

H

D

D

D

C

C

S

A

E

C

A

E

C

A

A

O

R

O

R

T

Payload

Payload

D

N

R

D

N

R

T

T

U

C

U

C

A

Data

Data

D

D

C

D

D

C

A

A

T

1

T

1

L

R

P

5

R

P

5

1

1

6

6

L

Data Packet

Data Packet

Token Packet

Token Packet

H/S Pkt

device detects token error

device has problem

control transfer
Control Transfer

H

H

D

S

D

C

A

E

C

E

A

8 bytes

R

A

D

N

R

SETUP

T

T

Setup

C

C

D

D

C

U

A

Data

1

K

R

P

5

P

0

6

Token Packet

Data Packet

H/S Pkt

H

D

H

D

C

A

E

C

A

R

A

I

D

N

R

Payload

DATA

T

C

C

N

D

D

C

Data

A

1

K

R

P

5

1

6

Data Packet

Token Packet

H/S Pkt

H

H

D

H

H

D

D

D

C

C

A

E

C

A

E

C

O

A

O

A

R

N

R

A

D

N

R

D

N

R

U

T

U

T

C

A

C

C

HANDSHAKE

D

D

C

D

D

C

T

A

T

A

1

K

1

K

R

P

5

R

P

5

1

1

6

6

Token Packet

Data Pkt

Token Packet

Data Pkt

H/S Pkt

H/S Pkt

Control operation

Control operation

not completed

completed

interrupt in out
Interrupt IN & OUT

H

D

H

H

D

H

D

D

C

C

A

E

C

A

E

C

A

A

A

A

R

R

Payload

Payload

I

D

N

R

I

D

N

R

T

C

T

C

C

C

N

D

D

C

N

D

D

C

Data

Data

A

K

A

K

1

1

R

P

5

R

P

5

1

0

6

6

Token Packet

Token Packet

Data Packet

Data Packet

H/S Pkt

H/S Pkt

good

good—note the data toggle

H

H

D

H

H

D

D

D

C

C

A

E

C

A

E

C

O

O

A

A

A

A

R

R

Payload

Payload

D

N

R

D

N

R

U

U

T

C

T

C

C

C

D

D

C

D

D

C

Data

Data

T

T

A

K

A

K

1

1

R

P

5

R

P

5

0

1

6

6

Token Packet

Token Packet

Data Packet

Data Packet

H/S Pkt

H/S Pkt

good

good—note the data toggle

Interrupt transfers are indistinguishable from BULK transfers. They occur at most once per frame.

isochronous transfer
Isochronous Transfer

H

D

D

C

A

E

C

Payload

A

R

I

D

N

R

T

C

Data

N

D

D

C

A

1

R

P

5

0

6

Token Packet

Data Packet

H

H

D

C

A

E

C

Payload

O

A

R

D

N

R

U

T

C

Data

D

D

C

T

A

1

R

P

5

0

6

Token Packet

Data Packet

Note: Always DATA0 PID, no ACK

standard usb requests
Get Status

Set Address

Get Descriptor

Set Descriptor

Get Configuration

Set Configuration

Get Interface

Set Interface

Set Feature

Clear Feature

Sync Frame

Standard USB Requests
class specific requests
Class Specific Requests
  • Specific to a given class, see the class specification for details.
  • Examples:
    • The Human Interface Device (HID) Class adds “Get Report and “Set Report” requests
    • The Hub Class adds a “Get Port Status” request
enumeration
Enumeration
  • The user plugs the device into a USB port.
  • The hub detects the device.
  • The host learns of the devices presence from the hub (Get Port Status Request)
  • The hub detects whether a device is Low speed or Full Speed.
  • The hub resets the device.
  • The host learns if a full speed device supports high speed.
  • The hub establishes a signal path between the device and the bus.
  • The host sends a Get Descriptor Request to learn the maximum packet size of the default pipe.
  • The host assigns an address (Set Address Request).
  • The host learn about a devices abilities (Get Descriptor Request).
  • The host assigns and loads a device driver.
  • The host’s device driver selects a configuration (Set Configuration Request).
host controller driver
Host Controller Driver
  • Fundamental component of Operating System support for USB
  • USB host controllers are PCI devices
  • What Does it Do?
    • Handles USB peripheral enumeration
    • Provides USB services for higher level drivers. All access to USB peripherals is via these services
which os s support usb
Which OS’s support USB
  • Pretty much all of them…More and more every day
    • Windows
    • MacOS
    • Linux
    • Solaris
    • VxWorks
windows 95 osr2 1
Windows 95 OSR2.1
  • Microsoft’s first attempt to support USB
  • Only available to OEMs
  • Full of bugs
  • No HID support
  • Avoid it!
windows 98 98se
Windows 98/98SE
  • First Microsoft OS with full USB support
  • Class drivers for HID and USB speakers
  • 98SE fixed a few minor bugs, enhanced performance, added class drivers for USB modems
windows me millennium
Windows Me (Millennium)
  • Windows 98 was supposed to be the last OS in the Win9x family, but...
  • Follow on to Windows 98
  • Adds performance tweaks, bug fixes, USB audio without clicks and pops, USB Mass Storage class driver
windows nt 4
Windows NT 4
  • NO SUPPORT FOR USB PROVIDED BY Microsoft!!!!
  • 3rd party NT 4 USB drivers are available
windows 2000
Windows 2000
  • Robust USB Support including USB 2.0 High Speed
  • Shares common driver model (WDM) with Windows 98
windows xp
Windows XP
  • Microsoft’s unified home/business operating system
  • Based on Windows 2000
  • Same basic USB support as Windows 2000 with some changes under the hood
  • Supports USB 2.0 High Speed
usb peripheral drivers
USB Peripheral Drivers
  • Class Drivers
    • Generic driver that supports a certain class of device
    • Human Interface Devices (HID), USB hubs, speakers, mass storage, modems
    • Note: Not all USB Classes that are defined by the USB-IF are implemented!!! Check your target OS for support. (i.e. I know of no OS that has implemented the Firmware Update Class)
  • Custom Drivers
    • Operating Systems often include vendor specific drivers that have passed certification (e.g. WHQL)
hid class
HID Class
  • Built into Windows 98 (or later)
  • No need to write (or install) a driver!
  • Used by mice and keyboards, but can be used for custom devices also.
  • Communicates with devices using reports
    • Set Report, Get Report
  • Full Spec at http://www.usb.org
    • You need the spec, and the HID Usage Tables
custom device driver options
Custom Device Driver Options
  • Look for an Open Source Device Driver
      • http://libusb-win32.sourceforge.net (Windows)
      • http://libusb.sourceforge.net (Linux and others)
  • Use a “General Purpose” Device Driver
  • Write a “Proprietary Custom Device” Driver (or have it written for you by a consultant)
generic usb device drivers for windows os s
Generic USB Device Drivers (for Windows OS’s)
  • Check your silicon manufacturer, they may have a general purpose driver you can use with their silicon (Cypress and FTDI both do)
  • Thesycon USBIO (http://www.thesycon.de)
  • MCCI Virtual COM port driver (http://www.mcci.com)
  • Jungo (http://www.jungo.com)
writing a device driver
Writing a Device Driver
  • Requires Specialized Knowledge (WDM and USBDI, Kernel Debuggers, etc.)
  • Long Learning Curve (i.e. >6months)
  • Not very well documented
  • Avoid this if you can!!!
certifications and logo s
Certifications and Logo’s
  • USB Implementers Forum Certification
    • Needed to use the new “USB Certified” Logos
      • Join the USB-IF or become a non-member Logo Licensee
      • Attend a “Plug-Fest” or have your device tested for compliance by an independent lab
  • Windows Hardware Quality Labs (WHQL) Certification
      • Download the HCT and run the applicable tests (if a self test is permitted for your device) or have your device tested for compliance by an independent lab
usb silicon options
USB Silicon Options
  • USB Transceiver Only
      • Cypress TX2, Phillips, etc.
      • These are primarily intended for FPGA’s that implement a Serial Interface Engine (SIE)
  • USB Transciever + SIE
      • Cypress SX2, Phillips, etc.
      • This would be a good option for DSP’s without USB support
  • USB Transciever + SIE + Microprocessor
      • Cypress EZ-USB, EZ-USB FX, EZ-USB-FX2, Microchip USB PIC, DSP’s that have USB Support
      • This would also be a good option for DSP’s without USB support
  • Fixed Function Devices
      • FTDI USB to Serial Converter Chips (This is a good option for DSP’s)
      • USB to ATAPI Bridge Chips
usb transfer types1
USB Transfer Types
  • Since some applications for Digital Signal Processing are “Stream” operations you might think that “Isochronous” transfers are the most appropriate type to use. Sometimes, but not always…Consider using RAM buffers and a Bulk or Interrupt Transfer Type.
  • In lower bandwidth applications, consider the FTDI USB to Serial Converter, they are a good shortcut if you can use them.
usb resources books
USB Resources: Books
  • Devices
    • Jan Axelson, USB Complete, Second Edition
    • John Hyde, USB Design By Example, Second Edition
  • Windows Drivers (including USB)
    • Walter Oney, Programming the Microsoft Windows Driver Model
    • Chris Cant, Writing Windows WDM Device Drivers
usb resources internet
USB Resources: Internet
  • www.usb.org
    • USB Specifications and Class Specifications
    • Draft docs
    • Bulletin board (Developer Forum)
    • Product information incl. chips
usb resources consultants
USB Resources: Consultants
  • J. Gordon Electronic Design
  • (763) 786-2405
  • http://www.jged.com
  • (A shameless plug for my employer)
optional topics if there is time
Optional Topics (if there is time)
  • Optical Isolation and USB
  • USB Tools
  • USB Serial Numbers and Windows XP
ad