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ISOUSB211: USB devices will be automatically remove to connect with computer after USB device is plug in computer USB port for about 10S

Part Number: ISOUSB211


     A USB device is designed to connect with computer via ISOUSB211. its connection path is  computer USB port ----usb device board( ISOUSB211-----USB communication IC).

   #1,when USB device board is plug in a computer USB port, the computer's device manager can indicate that USB device board is connected successfully, but after for about 10S, the USB device board will be automatically removed from computer(the USB device board is not listed in  computer device manager).

#2 if don't chose "allow the computer to turn off this device to save power" item in computer device manger, the USB device board can be kept connection with means the automatically un-connection issue is disappeared.let us describe this detailly

   At first , USB device board is plug in computer USB port, the computer's device manager can indicate the USB device board is connected successfully. then immediately open computer device manager\universal serial Bus Controllers\EMCC marketing Card(customer USB device board name)\properties\Power management (shown as attached picture), then un-chose   "allow the computer to turn off this device to save power" item , then the USB device board can be always listed in computer device manager. 


1. Does ISOUSB211's "Supports L1 (sleep) and L2 (suspend) low-power states" feature cause this issue? if yes, can this feature be disable ?

2.As   "allow the computer to turn off this device to save power" item in Windows system is chosen in default, any suggestion for customer board driver software to solve this issue?

  • Hi Ken,

    Thanks for reaching out. Please see my inputs below,

    1. From your description, I understand that the ISOUSB211 is being used on a peripheral board (device) which is connected to a computer (host) for use. Could you please confirm what is the peripheral product / application?
    2. Please note that ISOUSB211 stays transparent to both host and device and it primarily exchanges information from one side to the other without letting them feel its presence. i.e., the device will not know it is connected to ISOUSB211 and will think it is connect to the host directly and so does the host which thinks it is directly connected to the device. Since ISOUSB211 merely transfers information both sides, it doesn't get its own USB host / device like settings and its features can't be enabled / disabled.
    3. If a particular feature needs to be enabled / disabled, then that should be done in either the host or device and the same will be reflected on ISOUSB211 ports.
    4. ISOUSB211 does support L1 and L2 modes but it doesn't control those modes. The host / peripheral devices are responsible for putting one another in these modes by idling and ISOUSB211 just reflects the same.
    5. To disable this feature, you would have disable it in either the host / device and it seems like that is what you are doing in the computer device manager settings and that is working fine.
    6. I understand this is not a convenient way to avoid L1/L2 states, the alternative approach would be to take care of this in peripheral software and not let it idle long enough and avoid entering L1/L2 modes.

    I hope this explains the role of ISOUSB211 in this particular issue and that ISOUSB211 supports L1/L2 states but it doesn't control or influence them. Let me know if you have any other questions, thanks.

    Koteshwar Rao