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Embedded Software Development with eCos™ by Anthony J. Massa

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8.5. USB Support

Universal Serial Bus (USB) networks consist of a single host, called the Host Controller, and one or more slave devices. Slave devices connect to the USB through ports on specialized USB devices called hubs. The host initiates all USB operations. For example, if a host wants to receive data from a USB peripheral, the host issues an IN token to the peripheral. The slave peripheral then responds with the data or a NAK. USB slave peripherals cannot interact with each other. The current version of the USB specification is 2.0. USB supports four different types of communication:

  • Control Transfers— consist of standard, class, vendor, and reserved. All devices must respond to certain standard control messages.

  • Interrupt Transfers— ...

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