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Universal Serial Bus

Nov, 2010. Universal Serial Bus. MSG IMM applications team. USB Dual Role. Host responsibilities Provide 5v in the VBUS signal to power the device part sense D+ signal for a low-high transition and start the USB process. Device responsibilities

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Universal Serial Bus

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  1. Nov, 2010 Universal Serial Bus MSG IMM applications team

  2. USB Dual Role • Host responsibilities • Provide 5v in the VBUS signal to power the device part • sense D+ signal for a low-high transition and start the USB process • Device responsibilities • After power up sequence enable the pull-up resistor to inform to host that device is ready for enumeration process. How are we enabling USB Dual-Role? ID pin Floating – device mode Grounded – Host mode ID – grounded ID - Floating

  3. USB basic connections USB in Device mode (self powered) USB in Host mode USB in Device mode (bus powered) USB in Dual-role mode

  4. USB in Tower system

  5. USB Dual Role in Tower system

  6. Dual Role operation POR Disable 5v VBUS = 0V ID = Floating VBUS = 5V ID = grounded Load Device Support Load Host Support Enable pull-up resistor Enable 5v in VBUS USB Device working USB Host working VBUS = 0V ID = floating

  7. FAQ Difference between OTG and dual-role controller.  OTG: on the go, it is the protocol used EXCLUSIVELY for two devices that are OTG capable to interchange host and device roles dynamically without loosing connection. Dual role controller: a USB controller that can be either host or device in different connections. Some dual role controllers are OTG capable and some are not. Basic external USB hardware: pull-up resistor, series resistors in D+ and D- . Pull-up: better to use the internal resistor. Series 33 ohm resistors are recommended for impedance coupling with the USB cable. Ferrites are used to filter current peaks during connection.

  8. Reference Material USB.org Approved class specification documents http://www.usb.org/developers/devclass_docs Freescale Links Freescale USB Solutions http://www.freescale.com/usb Freescale USB stack with PHDC support http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MEDICALUSB&tid=vanmedicalusb Freescale MQX http://www.freescale.com/mqx

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