USB Enumeration problem
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From: mikecw_1968 on 23 Feb 2010 10:28 I have a USB device (development board with firmware) that I connect to using Hyperterminal (or Tera Term). When I power the device, connect it to the PC and bring up Hyperterminal, all is good. It enumerates and I can connect. At this point, if I cycle power on the device, after it comes up Hyperterminal will not communicate. I then kill Hyperterminal and bring it back up but the COM port that was enumerated earlier is no longer in the list of valid ports. At this point, I disconnect Hyperterminal, cycle power on the device then reconnect. All is well. What am I not understanding about the USB initialization/enumeration sequence? Btw, the PC is running Windows XP. Thanks. --------------------------------------- Posted through http://www.EmbeddedRelated.com
From: Joe Chisolm on 23 Feb 2010 18:54 mikecw_1968 wrote: > I have a USB device (development board with firmware) that I connect to > using Hyperterminal (or Tera Term). When I power the device, connect it to > the PC and bring up Hyperterminal, all is good. It enumerates and I can > connect. > > At this point, if I cycle power on the device, after it comes up > Hyperterminal will not communicate. I then kill Hyperterminal and bring it > back up but the COM port that was enumerated earlier is no longer in the > list of valid ports. > > At this point, I disconnect Hyperterminal, cycle power on the device then > reconnect. All is well. > > What am I not understanding about the USB initialization/enumeration > sequence? > > Btw, the PC is running Windows XP. > > Thanks. > > > > > --------------------------------------- > Posted through http://www.EmbeddedRelated.com Is your device using a CDC-ACM stack? If so, I had the same problem. It is not a enumeration problem but a Windows problem. If you hook the device to a Linux box with CDC-ACM support and use minicom, every thing will probably work fine. It has something to do with the way windows deals with USB serial. -- Joe Chisolm Marble Falls, Tx.
From: bigbrownbeastie on 24 Feb 2010 04:14
On Feb 23, 11:54 pm, Joe Chisolm <jchiso...(a)earthlink.net> wrote: > mikecw_1968 wrote: > > I have a USB device (development board with firmware) that I connect to > > using Hyperterminal (or Tera Term). When I power the device, connect it to > > the PC and bring up Hyperterminal, all is good. It enumerates and I can > > connect. > > > At this point, if I cycle power on the device, after it comes up > > Hyperterminal will not communicate. I then kill Hyperterminal and bring it > > back up but the COM port that was enumerated earlier is no longer in the > > list of valid ports. > > > At this point, I disconnect Hyperterminal, cycle power on the device then > > reconnect. All is well. > > > What am I not understanding about the USB initialization/enumeration > > sequence? > > > Btw, the PC is running Windows XP. > > > Thanks. > > > --------------------------------------- > > Posted throughhttp://www.EmbeddedRelated.com > > Is your device using a CDC-ACM stack? If so, I had the same problem. > It is not a enumeration problem but a Windows problem. If you hook the > device to a Linux box with CDC-ACM support and use minicom, every thing > will probably work fine. It has something to do with the way > windows deals with USB serial. > > -- > Joe Chisolm > Marble Falls, Tx. There are some fixes around for this and involves WinXP SP3 |