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

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

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

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 50-90 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 30-100 KB of code storage, and 10-100 KB of runtime memory. PCB Footprint: Embedded USB host controllers are typically in 80-128 pin packages

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

Linux Boards- Comparison FOX Board VIPER PC/104-compliant Software Features: Kernel Full Linux ver 2.4.31 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) 1.9W @ + 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