On Tuesday 12 June 2007, Vortex wrote: >Hello Alan, > >> The 500000 status means Babble and Stalled. In other words, the >> computer's USB controller detected signals on the USB bus at a time >> when the device should not have been sending anything. Maybe the >> signals were electrical noise, or maybe the controller's detection >> circuitry isn't working right. > >Thank you for this very helpful hints! >I had a look at the waveforms on the USB-Bus and discovered >that the impedance between my hardware and the laptop is >completely missmatched. According to an example application design from >dallas semiconductor i used 2x30pF on D+ and D-. But on the Notebook >side there are about 300pF. After matching this, everything >works perfectly. Don't know which one of the two devices is the bad >one now but it works....
My guess is that the notebook got the 300pf caps more as an appeasement to the fcc and its radiated noise specs than for any good engineering reasons. It wouldn't even be the 1,000,000th time as its very commonly done. That, and it may actually help the system to tolerate crappy cable whose impedance is not well controlled or even defined. It obviously will also cut the maximum cable length it can still function with drasticly. Nothing beats a 1/1 vswr, but in commonly used computer cabling its often worse than 3/1. >Best wishes, >Klaus > >------------------------------------------------------------------------- >This SF.net email is sponsored by DB2 Express >Download DB2 Express C - the FREE version of DB2 express and take >control of your XML. No limits. Just data. Click to get it now. >http://sourceforge.net/powerbar/db2/ >_______________________________________________ >linux-usb-devel@lists.sourceforge.net >To unsubscribe, use the last form field at: >https://lists.sourceforge.net/lists/listinfo/linux-usb-devel -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) A bit of talcum Is always walcum -- Ogden Nash ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
