Maximum transfer rate using isochronous tranfers [USB]

[eng22]

Posted on April 15, 2009 at 16:38

Maximum transfer rate using isochronous tranfers [USB]

[eng22]

Posted on May 17, 2011 at 13:09

Hi USB experts, I´ve been trying to use the USB peripheral in isochronous mode.

I´m being able to comunicate properly but I can´t get the transfer rate I need. The problem seems to be with the size of the packet memory area. It size is 512 bytes, and since I´m using 64 bytes for each buffer (TX and RX) of the endpoint 0, there is only 384 bytes left for my double buffered isochronous endpoint. I need to tranfer 288 bytes each frame (one frame per millisecond). Can anyone tell me if this really is a limitation or if there some way to make it? Thanks.

[brunoalltest]

Posted on May 17, 2011 at 13:09

I´m not an expert, but I´ve been working with isochronous tranfers too.

I think this is really a limitation. :( But maybe you can save a few bytes if you downsize your control packet to 32 ou 16 bytes.[ This message was edited by: brunoalltest on 11-04-2009 18:04 ]

[eng22]

Posted on May 17, 2011 at 13:09

I´m not sure whether is possible to send multiple packets in one frame. If you look at ''Table 5-4. Full-speed Isochronous Transaction Limits'' over USB specification revision 2.0, for a data payload of 16 bytes theres a Max transfer of 60 packets achieving a total max bandwith of 960000 bytes/sec.

But I don´t have any idea if I got the idea right neither if it is possible using the STM32. Maybe some user or moderator can tell us if this is possible and explain how to do it. I couln´d find any other informations on the rm0008, um0424 or um0427. Thanks

[eng22]

Posted on May 17, 2011 at 13:09

I couldn´t find any solution yet.

Please, if anybody can help I´ll appreciate. Thanks