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I have a USB to ethernet chip (USB 2.0 480 Mb/s) and a microcontroller (MSP430F550x family, full-speed USB 12 Mb/s) that connects to a USB hub (USB 2.0 480 Mb/s).

How would I make these work together? Will the USB hub go at the slowest speed, which would be the microcontroller? Is there any way I can have everything work together at 480 Mb/s?

Thanks in advance for your help!

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The USB protocol will solve the speed problem for you, the faster element (USB-ethernet chip or HUB) will use the slower protocol (because the faster protocol 'contains' the slower protocol as a required fall-back).

Your real problem will be the driver sooftware: do you have a driver for this USB-ethernet chip that can run on your MSP uC?

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Unless I'm reading the wrong document (quite possible) the MSP430F550x family doesn't have a USB host interface, only USB device.

Therefore it would seem that both this processor and your ethernet interface are plugged into downstream hub ports, and something else like a PC or more powerful microcontroller is plugged in upstream as the ultimate host device.

Assuming the upstream device and hub support USB2, the ethernet adapter would be able to take advantage of that, while traffic intended for your micro would be sent at the slower USB full speed. There would be no communication between the two devices, other than any transfers between them done by the ultimate host in software.

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  • \$\begingroup\$ you're right, the microcontroller would be a usb device, and the PC would be the host. since the datasheet shows USB input and output ports, this means that the microcontroller would be able to communicate using USB right? \$\endgroup\$ – Jack Aug 13 '12 at 21:02
  • \$\begingroup\$ With the pc, if you get the software right, yes \$\endgroup\$ – Chris Stratton Aug 13 '12 at 21:14
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I've found that the USB hub chip I'm using has transaction translators (TT) that essentially speed up the slowest device to match the speed of the host. In my case, if the host was a PC with USB 2.0, then I wouldn't have to worry about the microcontroller, for example, being slower.

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