USB 1.1 host

Does anybody know if the USB standard allows connection between USB 1.1 host with USB 2.0 peripheral ?

I know that you can connect the USB 1.1 peripheral device to USB 2.0 host PC.


Martin Roth Motorola Israel

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Martin Roth
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I'm not sure. The USB 2.0 peripheral answers with a device descriptor that identifies it as a USB 2.0 device, and the 1.1 host cannot understand this. If you can somehow configure the peripheral to identify itself as a 1.1 device, then it will operate smoothly.

A later revision host is always backwards compatible. Thus a USB 2.0 host can accept connections from USB 1.1 peripherals. This is because the 1.1 device sends a descriptor that the host can understand (version 2.0 host can read version 1.1 device descriptor)

Hope this helps, Antti Keskinen

Reply to
Antti Keskinen

"Martin Roth" skrev i meddelandet news:ct8gv0$bm3$

I certainly have connected USB 2.0 High Speed USB Memories to my USB 1.1 PC

Best Regards
Ulf at atmel dot com
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Reply to
Ulf Samuelsson

The USB 2.0 spec requires that high speed devices fall back to full speed. When the bus is reset for a new device, the device "chirps" at a rate too high for full speed detection (during reset). If the host does not detect the device as high speed (say there was a full speed only hub between the host and the device), The host will enumerate the device at full speed.

Older host hardware will never even know that the device was supposed to run at high speed, it will just work at full speed.

Advertisement: check out my new lowspeed/fullspeed USB bus sniffer that will run from any browser:

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Regards ~Steve

Reply to
Steve Calfee

You've trained your CAT to log USB packets and POST THE LOGS on the INTERNET?

He looks like he's concentrating hard too ...

formatting link
.. do you reckon he'd be able to note down at least the first few bytes of the high speed packets if he _really_ tried.

Sorry. Nice product BTW, but I can usually get by with a software logger like USBMON and printfs on the device.


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