Comprei um adaptador wi-fi ralink5370. ele se desconecta aleatoriamente.
na verdade, eu entendo isso de lsusb quando está conectado ou não.
Estou executando o ubuntu 14.04.2 no mínimo.
esta é a minha saída dmesg depois de conectá-lo:
[ 5564.693869] usb 3-6: new high-speed USB device number 98 using xhci_hcd
[ 5564.728096] usb 3-6: New USB device found, idVendor=148f, idProduct=5370
[ 5564.728106] usb 3-6: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 5564.728111] usb 3-6: Product: 802.11 n WLAN
[ 5564.728116] usb 3-6: Manufacturer: Ralink
[ 5564.728120] usb 3-6: SerialNumber: 1.0
[ 5564.841932] usb 3-6: reset high-speed USB device number 98 using xhci_hcd
[ 5564.868994] xhci_hcd 0000:00:14.0: xHCI xhci_drop_endpoint called with disabled ep ebfa442c
[ 5564.869003] xhci_hcd 0000:00:14.0: xHCI xhci_drop_endpoint called with disabled ep ebfa4400
[ 5564.869009] xhci_hcd 0000:00:14.0: xHCI xhci_drop_endpoint called with disabled ep ebfa4458
[ 5564.869013] xhci_hcd 0000:00:14.0: xHCI xhci_drop_endpoint called with disabled ep ebfa4484
[ 5564.869018] xhci_hcd 0000:00:14.0: xHCI xhci_drop_endpoint called with disabled ep ebfa44b0
[ 5564.869022] xhci_hcd 0000:00:14.0: xHCI xhci_drop_endpoint called with disabled ep ebfa44dc
[ 5564.869026] xhci_hcd 0000:00:14.0: xHCI xhci_drop_endpoint called with disabled ep ebfa4508
[ 5564.869386] ieee80211 phy88: rt2x00_set_rt: Info - RT chipset 5390, rev 0502 detected
[ 5564.880195] ieee80211 phy88: rt2x00_set_rf: Info - RF chipset 5370 detected
[ 5564.880582] ieee80211 phy88: Selected rate control algorithm 'minstrel_ht'
[ 5564.913832] ieee80211 phy88: rt2x00lib_request_firmware: Info - Loading firmware file 'rt2870.bin'
[ 5564.913844] systemd-udevd[15166]: renamed network interface wlan0 to wlan1
[ 5564.913863] ieee80211 phy88: rt2x00lib_request_firmware: Info - Firmware detected - version: 0.29
[ 5565.068340] IPv6: ADDRCONF(NETDEV_UP): wlan1: link is not ready
[ 5567.698146] usb 3-6: USB disconnect, device number 98
[ 5568.120607] usb 3-6: new full-speed USB device number 99 using xhci_hcd
[ 5568.120752] usb 3-6: Device not responding to set address.
[ 5568.324546] usb 3-6: Device not responding to set address.
[ 5568.528370] usb 3-6: device not accepting address 99, error -71
[ 5568.640382] usb 3-6: new full-speed USB device number 100 using xhci_hcd
[ 5568.640525] usb 3-6: Device not responding to set address.
[ 5568.844406] usb 3-6: Device not responding to set address.
[ 5569.048173] usb 3-6: device not accepting address 100, error -71
[ 5569.160199] usb 3-6: new full-speed USB device number 101 using xhci_hcd
[ 5569.160351] usb 3-6: Device not responding to set address.
[ 5569.364230] usb 3-6: Device not responding to set address.
[ 5569.568039] usb 3-6: device not accepting address 101, error -71
[ 5569.680011] usb 3-6: new full-speed USB device number 102 using xhci_hcd
[ 5569.680156] usb 3-6: Device not responding to set address.
[ 5569.884019] usb 3-6: Device not responding to set address.
[ 5570.087833] usb 3-6: device not accepting address 102, error -71
[ 5570.087910] hub 3-0:1.0: unable to enumerate USB device on port 6
[ 5575.373939] usb 3-5: new full-speed USB device number 103 using xhci_hcd
[ 5575.374052] usb 3-5: Device not responding to set address.
[ 5575.578001] usb 3-5: Device not responding to set address.
[ 5575.781728] usb 3-5: device not accepting address 103, error -71
[ 5575.893751] usb 3-5: new full-speed USB device number 104 using xhci_hcd
[ 5575.893863] usb 3-5: Device not responding to set address.
[ 5576.097787] usb 3-5: Device not responding to set address.
[ 5576.301606] usb 3-5: device not accepting address 104, error -71
[ 5576.413609] usb 3-5: new full-speed USB device number 105 using xhci_hcd
[ 5576.413754] usb 3-5: Device not responding to set address.
[ 5576.617597] usb 3-5: Device not responding to set address.
[ 5576.821391] usb 3-5: device not accepting address 105, error -71
[ 5576.933380] usb 3-5: new full-speed USB device number 106 using xhci_hcd
[ 5576.933529] usb 3-5: Device not responding to set address.
[ 5577.137411] usb 3-5: Device not responding to set address.
[ 5577.341203] usb 3-5: device not accepting address 106, error -71
[ 5577.341301] hub 3-0:1.0: unable to enumerate USB device on port 5
[ 5582.503394] usb 3-6: new full-speed USB device number 107 using xhci_hcd
[ 5582.503542] usb 3-6: Device not responding to set address.
[ 5582.707400] usb 3-6: Device not responding to set address.
[ 5582.911185] usb 3-6: device not accepting address 107, error -71
[ 5583.023156] usb 3-6: new full-speed USB device number 108 using xhci_hcd
[ 5583.023293] usb 3-6: Device not responding to set address.
[ 5583.227231] usb 3-6: Device not responding to set address.
[ 5583.430997] usb 3-6: device not accepting address 108, error -71
[ 5583.543024] usb 3-6: new full-speed USB device number 109 using xhci_hcd
[ 5583.543172] usb 3-6: Device not responding to set address.
[ 5583.747020] usb 3-6: Device not responding to set address.
[ 5583.950806] usb 3-6: device not accepting address 109, error -71
[ 5584.062830] usb 3-6: new full-speed USB device number 110 using xhci_hcd
[ 5584.062977] usb 3-6: Device not responding to set address.
[ 5584.266802] usb 3-6: Device not responding to set address.
[ 5584.470611] usb 3-6: device not accepting address 110, error -71
[ 5584.470681] hub 3-0:1.0: unable to enumerate USB device on port 6
[ 5599.313295] usb 3-5: new full-speed USB device number 111 using xhci_hcd
[ 5599.313439] usb 3-5: Device not responding to set address.
[ 5599.517317] usb 3-5: Device not responding to set address.
[ 5599.721106] usb 3-5: device not accepting address 111, error -71
[ 5599.833114] usb 3-5: new full-speed USB device number 112 using xhci_hcd
[ 5599.833257] usb 3-5: Device not responding to set address.
[ 5600.037121] usb 3-5: Device not responding to set address.
[ 5600.240943] usb 3-5: device not accepting address 112, error -71
[ 5600.352943] usb 3-5: new full-speed USB device number 113 using xhci_hcd
[ 5600.353091] usb 3-5: Device not responding to set address.
[ 5600.556943] usb 3-5: Device not responding to set address.
[ 5600.760724] usb 3-5: device not accepting address 113, error -71
[ 5600.872722] usb 3-5: new full-speed USB device number 114 using xhci_hcd
[ 5600.872873] usb 3-5: Device not responding to set address.
[ 5601.076722] usb 3-5: Device not responding to set address.
[ 5601.280540] usb 3-5: device not accepting address 114, error -71
[ 5601.280621] hub 3-0:1.0: unable to enumerate USB device on port 5
Este é um "bandaid", mas pode ser uma correção para você. instale o ndis-wrapper e baixe o driver do Windows para o seu adaptador WiFi USB e use o ndis wrapper para importar o driver para o Ubuntu.
Você pode encontrar o ndis wrapper e o gui no Ubuntu Software Center deixe-me saber se isso ajuda.