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USB

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)

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USB

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  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 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

  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

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