Ports and Interfaces > USB

basic USB enumeration question

<< < (2/2)

Jan Axelson:
In a quick search of the spec, I found no requirement for a polling interval for this request.

Jan

MattCarp:
Thanks again!

Also, in reviewing the book again, I found the content in the fourth edition on page 383 (chapter 15) that covers the host's checking hub status to begin the enumeration process!

Barry Twycross:
If Linux is doing Get Hub Status requests as a poll, that's a little weird. A hub has a status change interrupt endpoint, which is the normal way of getting notifications. The polling rate of the interrupt endpoint is specified as "FFH (Maximum allowable interval)" (Section 11.23.1) which is wrong as the maximum allowable poll for a high speed device is 16, which works out at around 4 sec I think, though most implementations won't poll an interrupt endpoint that slowly.

Jan Axelson:
Hi Barry,

You're right of course. I wasn't thinking about the interrupt endpoint for some reason.

Jan

mdlayt:
I wouldn't bother trying to put specs on the host (unless you are writing the host code, of course--in that case, by all means, meet the spec).

I'm certain I've seen my device suspend at times when the host (Win XP) had no business allowing it to suspend.

I think I can also say that it shouldn't take two or three seconds after you plug in a device (based on the USB spec) before you can connect to it from an app.

I'm curious what the guys doing audio have found.

I think you can plan that hosts will generally do things in a timely fashion, where timely fashion is defined as as:  how your host typically behaves, up to 100% slower.

Navigation

[0] Message Index

[*] Previous page