24. USB Device Port (UDP)

In the current revision of the AT91SAM9G45 USB High speed is not working. It will work in the processor's next revision, which is expected in august 2011. The Stamp9G45 integrates one USB device port supporting speeds up to 480 MBit/s. It is multiplexed with the USB Host Port B. Only one of them can be used at a time.

The controller is fully compliant with the Enhanced HCI(EHCI) specification. It supports both High-speed 480 Mbps and Full-speed 12 Mbps devices.

The USB Device Port (UDP) is compliant with the Universal Serial Bus (USB) V2.0 full-speed device specification. The USB device port enables the product to act as a device to other host controllers.

The USB device port can also be implemented to power on the board. One I/O line may be used by the application to check that VBUS is still available from the host. Self-powered devices may use this entry to be notified that the host has been powered off. In this case, the pullup on DP must be disabled in order to prevent feeding current to the host. The application should disconnect the transceiver, then remove the pullup.