PORTS Forum

Ports and Interfaces => USB => Topic started by: GIDONG on May 17, 2011, 05:15:46 am

Title: USB standard start up sequeance
Post by: GIDONG on May 17, 2011, 05:15:46 am

hi,

I'm developing a USB device and i'm having trouble to determine if I'm complaint with the USB standard.
My start up sequence is as followers:

* Configure clocks
* Init USB stack, enable relevant interrupts and handle all host requests
* a user start up menu comes up
* if the user changed clock configuration - reconfigure clocks and reset the USB

Is this reset allowed by the standard ?
Is this reset allowed in the middle of an enumeration sequence ?

Thanks

Title: Re: USB standard start up sequeance
Post by: Jan Axelson on May 17, 2011, 10:24:57 am

I'm not sure what you mean by "reset the USB" on the device.

To restart enumeration, you need to emulate detach and reattach to the bus.

Jan

Title: Re: USB standard start up sequeance
Post by: GIDONG on May 17, 2011, 10:48:33 am

hi,
thanks for the quick replay.
indeed "reset the USB" - I meant to emulate by SW a detach and reattach of the device.

the device is BUS powered.
I run this with the USB command verifier and I pass the Chapter 9 tests, but I reset the USB only at start up - so I think the command verifier doesn't see this at all, it happens before i run the test.

Thanks