On Mon, 28 Mar 2005, James Lamanna wrote: > Earlier I posted about having long delay issues when reading back > bytes from a FTDI 232BM USB->Serial chip. > Now, I've noticed that after a long period of time of semi-continual > use (maybe 8+ hours) I see the following messages in my kernel.log: > > Mar 24 23:46:42 displaytest kernel: hub 2-0:1.0: port 2 disabled by > hub (EMI?), re-enabling... > Mar 24 23:46:42 displaytest kernel: usb 2-2: USB disconnect, address 4 > Mar 24 23:46:42 displaytest kernel: ftdi_sio 2-2:1.0: device disconnected > Mar 24 23:46:42 displaytest kernel: usb 2-2: new full speed USB device > using address 5 > Mar 24 23:46:42 displaytest kernel: ftdi_sio 2-2:1.0: FTDI FT232BM > Compatible converter detected > Mar 24 23:46:42 displaytest kernel: usb 2-2: FTDI FT232BM Compatible > converter now attached to ttyUSB1 > > Of course I have a test program running overnight and when the device > comes back up it switches device names (because my test program has > the port still open), which causes it to die at that point. > > Is there any particular reason the hub would disable that port? Or am > I in flakey hardware land here?
There are a few reasons why a hub would disable a port, but they all boil down to hardware problems of one sort or another. Basically the idea is if the hub thinks the device attached to the port is transmitting when it's not supposed to be, the hub disables the port. Why would the hub think that? One obvious cause would be the device malfunctioning. Another would be the hub malfunctioning. A more likely alternative is electrical noise in the cable appearing to be a signal at a time when there should only be silence. Alan Stern ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
