PORTS Forum

Ports and Interfaces => USB => Topic started by: leeqm on January 16, 2013, 08:00:06 pm

Title: Low speed USB 2.0 device BOS descriptor
Post by: leeqm on January 16, 2013, 08:00:06 pm

Hi,


We have a low speed USB HID device failed the BOS descriptor test recently, it turns out have to change in firmware, after reading the USB3.0 spec, still not sure , how to define a BOS descriptor to satisfy the USB2.0 CV test.

Can you help ?

Thanks

Leeqm

Title: Re: Low speed USB 2.0 device BOS descriptor
Post by: Jan Axelson on January 16, 2013, 10:15:40 pm

If you can post your descriptor and provide the error message when it failed, someone might be able to help.

Title: Re: Low speed USB 2.0 device BOS descriptor
Post by: Barry Twycross on January 17, 2013, 04:52:50 pm

You shouldn't need a BOS descriptor if you don't declare you have one.

A device should only have one if it declares its bcdUSB in the device descriptor is 0210H or greater. (Sec 9.2.6.6 of the USB 3 spec). So if you declare yourself as a plain old USB 2 device (bcdUSB 0200H), then you shouldn't get bothered for it.

Also if you don't support it and someone asks for it, the request should be STALLed. Does you device do that?