PORTS Forum

Ports and Interfaces => USB => Topic started by: RR on September 20, 2010, 08:04:09 pm

Title: USB Communication Problem with hub
Post by: RR on September 20, 2010, 08:04:09 pm

Hi,

I am communicating my device with Host(Desktop) via USB. The device is connected via a hub to the PC. My Device use the communication class device interface. I use real term/Hyper term to communicate from Host to device. Sometimes when i try to open the port, it fails and gives an error message. The failure doesnt occur when the device connects directly to the PC. Help me to resolve the issue.

Regards,
Johncy

Title: Re: USB Communication Problem with hub
Post by: Ron Hemphill on September 21, 2010, 10:05:34 am

What type of error message do you get, and exactly what is the error?

Title: Re: USB Communication Problem with hub
Post by: RR on September 21, 2010, 12:46:01 pm

With realterm, I get the error message as "A device attached to the system is not functioning"

Title: Re: USB Communication Problem with hub
Post by: Ron Hemphill on September 21, 2010, 05:30:50 pm

Interesting issue.  Hubs quite often mask USB device problems rather than expose them.

Can you give us a little more information about the device?  Is it a device you are developing and have just now encountered this issue with the hub?  Is it a full-speed device?  Is the host Windows?  If so, what version of Windows and what service pack is installed?  How about the hub itself.  Can we assume it is a high-speed hub?

Title: Re: USB Communication Problem with hub
Post by: Guido Koerber on September 21, 2010, 06:30:21 pm

Actually a USB 2.0 hub to which a low or full speed device is connected can handle the individual packets of a control transfer faster than a UHCI host and in some cases even faster than a OHCI host. I did run into such an issue a couple years ago, it turned out my USB stack had a race condition that was exposed only with certain USB 2.0 hubs.

Title: Re: USB Communication Problem with hub
Post by: RR on September 23, 2010, 01:38:49 am

Hi Guido Koerber,

Greetings!!

When I look at the trace, ACK is received for my SetControlLineState. (For this message from our software we sent response via SeriaState message). But this SerialState response is not received. Do you have any resolution for the issue?

My device is Full speed device. Hub is High speed. Host is Win XP or Win 7.

Regards,
Johncy.

Title: Re: USB Communication Problem with hub
Post by: RR on September 23, 2010, 01:47:38 am

Hi Ron,

Device - Full speed
Hub - High speed
Host - Win XP/Win 7

Regards,
Johncy.

Title: Re: USB Communication Problem with hub
Post by: Guido Koerber on September 23, 2010, 03:33:40 am

Use a hardware bus analyzer to check what is really going on on the bus.