PORTS Forum

Ports and Interfaces => USB => Topic started by: jb on June 13, 2022, 05:47:46 pm

Title: Is there a difference between "null packet" and "zero-length packet"?
Post by: jb on June 13, 2022, 05:47:46 pm

USB Audio, MIDI, and Debug Class specs mention null packets (https://www.google.com/search?client=firefox-b-1-d&q=site%3AUSB.org+%22null+packet%22):

Quote

In any case, the
endpoint is required to support null packets. This bit must be used by the Host software to determine if the
driver should pad all potential short packets (except null packets) with zero bytes to wMaxPacketSize
length before sending them to an OUT endpoint.

but don't define it anywhere that I can see. Is it the same thing as a zero-length packet?

Title: Re: Is there a difference between "null packet" and "zero-length packet"?
Post by: Jan Axelson on June 15, 2022, 03:52:28 pm

same thing