1. USB The topics covered, in order, are USB background
Is USB the right solution?
Hardware issues
Software issues

2. A Quick USB Background
Three data rates are supported – low speed (1.5Mbit/sec), full speed (12Mbit/sec), and high speed (480 Mbit/sec)
One host, many peripherals. The host controls all USB operations-sending data to and requesting data and status.
The USB cabling can carry power as well as data
Data transfer
Bulk Transfers
Control Transfers
Isochronous Transfers
Interrupt transfers
Hot pluggability, no pre-configuration – USB OTG

3. Is USB The Right Solution?
Host or peripheral application needs to adhere to one of the class standards.
OS and USB software

4. Can Your Hardware Support USB?
Bus Access: will need 8, 16, or 32 bits of address and data to connect a USB host controller. In order to move data efficiently, this memory space will need access times on the order of nanoseconds
System Throughput: Multiple host ports on one host controller will increase the load 
Interrupt Load: Full-speed and low-speed USB have frame intervals of 1 ms, Highspeed USB uses a microframe interval of 125 microseconds
Memory: A robust USB stack may take KB of code storage, and KB of runtime memory.
PCB Footprint: Embedded USB host controllers are typically in pin packages

5. USB Software Needs
Operating systems that have a native USB stack –eg. Linux and Microsoft’s WinCE
Operating systems that do not have a native USB stack - Third party vendors may provide stacks for some USB controllers
What if there is no operating system at all?  
USB peripherals - only respond to commands from the host – no underlying OS support.
The USB host protocol – requires RTOS for enumerating a device, handling asynchronous events, generating command packets

6. Linux Boards- Comparison
FOX Board
VIPER
PC/104-compliant
Software Features:
Kernel
Full Linux ver
Embedded Linux v2.6
Language
C, C++, PHP, PYTHON
Tools
GNU C compiler
Hardware Features:
Data Transfer Rate
USB 1.1 (low speed & full speed )
Memory
8MB FLASH 32MB RAM
Up to 64Mbytes
64MB SDRAM
Ports
2 USB 1.1
Dual USB host ports - v1.1
USB Host and USB Slave ports
Power
5 Volt 280mA (1 watt)
+ 5V only
Cpu
Axis ETRAX 100LX 32 bit, RISC, 100MHz (100MIPS)
pins sockets
Two 40 pins sockets
40 digital I/O lines
Other Interface
I²C interface
I2C/I2S bus