Registry not updating with frequent removal of USB device RRS feed

  • Question

  • Hi, we have a custom PCB which runs WEC2013.  The PCB includes a miniPCIe interface into which we plug a wireless modem.  This miniPCIe is connected to a USB hub on the PCB.

    When the wireless modem is first inserted, it is detected and a serial port (COM9:) is created on the system (we can see the entry under HKLM\Drivers\Active). 

    We have the ability to toggle the power supply to the miniPCIe card through software. When we turn the power off, we see that the registry is updated and COM9: disappears.  When we power it back on, the registry is again updated and COM9: reappears. 

    But if we do this repeatedly (sometimes after 30 repeats, sometimes after 3000 repeats) then the registry no longer updates and COM9: becomes 'stuck' in the registry.  Our application is able to open COM9: (because it is present in the registry) but we can't communicate with the modem.  So it looks as though the registry is frozen.  However, if we plug a USB memory stick into another USB port (on another USB hub), then this does appear under HKLM\Drivers\Active, and our app can read/write to the USB memory stick.

    Can someone point me at a description of the stages followed in handling the insertion of a USB device, or suggest how we can overcome this?  Our system needs to run reliably over a long period of time and rebooting the system is not really an option to being it back into operation.

    Friday, May 1, 2020 11:56 AM

All replies

  • It is unlikely that this is a registry problem.

    Let's back up a bit.  For anything to happen, there will need to be an interrupt and that interrupt will need to be seen by the kernel - have you checked that yet?  Is the interrupt still enabled?  I wouldn't be surprised if this is either a hardware problem, or an interrupt enable problem.  Neither of which you have mentioned debugging.

    Bruce Eitman
    Senior Enginer
    Bruce.Eitman AT Synopsys DOT com
    My BLOG http://geekswithblogs.net/bruceeitman
    I work for

    Friday, May 1, 2020 12:08 PM
  • Thanks Bruce.  We will look into that.
    Friday, May 1, 2020 12:12 PM