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Thread: USB / serial converter doesn't show up

  1. #1
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    USB / serial converter doesn't show up

    Hello all,
    I have two different USB to serial converters that normally work, but sometimes they simply stop working and nothing short of a reboot will make them work again.

    I always get this error when I replug the device(s):
    Code:
    $ tail -f /var/log/syslog
    kernel: [116743.620062] usb 6-1: new full-speed USB device number 5 using ohci_hcd
    kernel: [116743.789650] pl2303 6-1:1.0: pl2303 converter detected
    udevd[22894]: failed to execute '/lib/udev/mtp-probe' 'mtp-probe /sys/devices/pci0000:00/0000:00:13.1/usb6/6-1 6 5': No such file or directory
    kernel: [116743.811481] usb 6-1: pl2303 converter now attached to ttyUSB0
    kernel: [116743.873337] pl2303 ttyUSB0: pl2303 converter now disconnected from ttyUSB0
    kernel: [116743.873352] pl2303 6-1:1.0: device disconnected
    kernel: [116744.411021] usb 6-1: usbfs: process 4191 (EMT-2) did not claim interface 0 before use
    
    $ ll /dev/ttyUSB*
    ls: cannot access /dev/ttyUSB*: No such file or directory
    
    $ ll /lib/udev/mtp-probe
    ls: cannot access /lib/udev/mtp-probe: No such file or directory
    
    $ lsusb
    Bus 006 Device 005: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port\
    ...
    The devices are a Trendnet TU-S9 and a Unitek but they both show up identical. I've also tried "sudo service uvdev restart" to no avail. I don't want to reboot !
    Last edited by dargaud; May 24th, 2013 at 03:57 PM.

  2. #2
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    Re: USB / serial converter doesn't show up

    When the device is plugged in, the system (perhaps following a udev rule) tries to run the 'mtp-probe' application.

    However, you don't seem to have the 'mtp-probe' application installed, so the rule fails, and the mount fails.

    mtp-probe is provided by the libmtp-runtime package, which is a dependency of the libmtp9 package, which is in turn a dependency of many audio players link banshee and rhythmbox.

  3. #3
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    Re: USB / serial converter doesn't show up

    Then why do those converters work the first time I plug them in but fail after the 2nd time ?

    I did remove libmtp-runtime a while ago because it was causing trouble with an Android device, blocking the possibility to mount as mass storage. I just added it back, but no change:
    Code:
    kernel: [155131.056138] usb 5-3: new full-speed USB device number 9 using ohci_hcd
    kernel: [155131.224425] pl2303 5-3:1.0: pl2303 converter detected
    mtp-probe: checking bus 5, device 9: "/sys/devices/pci0000:00/0000:00:13.0/usb5/5-3"
    kernel: [155131.246572] usb 5-3: pl2303 converter now attached to ttyUSB0
    mtp-probe: bus: 5, device: 9 was not an MTP device
    kernel: [155131.317526] pl2303 ttyUSB0: pl2303 converter now disconnected from ttyUSB0
    kernel: [155131.317547] pl2303 5-3:1.0: device disconnected
    kernel: [155131.840623] usb 5-3: usbfs: process 4191 (EMT-2) did not claim interface 0 before use

  4. #4
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    Re: USB / serial converter doesn't show up

    Quote Originally Posted by dargaud View Post
    kernel: [155131.246572] usb 5-3: pl2303 converter now attached to ttyUSB0
    mtp-probe: bus: 5, device: 9 was not an MTP device
    The device you are plugging in is not recognized as an MTP device.
    Is that just the serial adapter?
    Or is that the device at the other end of the serial cable?
    What device is it?

    Some devices may require a shim.
    Some devices are not really MTP.
    Some pl2303 adapters, especially cheap ones, are knockoffs (fakes) that lack full functionality.

  5. #5
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    Re: USB / serial converter doesn't show up

    After a reboot the USB/serial adapter registers itself as /dev/ttyUSB0 and works again. From the syslog:
    Code:
    kernel: [  544.944074] usb 5-3: new full-speed USB device number 2 using ohci_hcd                
    mtp-probe: checking bus 5, device 2: "/sys/devices/pci0000:00/0000:00:13.0/usb5/5-3"                 
    mtp-probe: bus: 5, device: 2 was not an MTP device                                                   
    kernel: [  545.179123] usbcore: registered new interface driver usbserial
    kernel: [  545.179166] USB Serial support registered for generic
    kernel: [  545.179241] usbcore: registered new interface driver usbserial_generic
    kernel: [  545.179246] usbserial: USB Serial Driver core
    kernel: [  545.181377] USB Serial support registered for pl2303
    kernel: [  545.181461] pl2303 5-3:1.0: pl2303 converter detected
    kernel: [  545.202394] usb 5-3: pl2303 converter now attached to ttyUSB0
    kernel: [  545.202450] usbcore: registered new interface driver pl2303
    kernel: [  545.202456] pl2303: Prolific PL2303 USB to serial adaptor driver
    So what is it that keeps it from working again after a 1st failure. And about the possibility of it being a fake, I have two of different brands...

  6. #6
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    Re: USB / serial converter doesn't show up

    Are you asking "Why, after the first failure, does it continue to fail?"
    That answer seems self-evident.

    From the log you showed, the kernel's perspective is that it does not recognize the MTP device. Of course, the kernel assumes that the serial-USB adapter is working properly.

    So you have four possibilities.
    1) The kernel and adapter are working properly and the MTP device is not known to the kernel.
    2) The kernel and adapter are working properly and the device is not really an MTP-compatible device.
    3) The adapter is faulty.
    4) Kernel bug.

    If you really want a solution, eliminating several of those possibilities is a good first step. For example, it's not difficult to determine if #1 and #2 are true/false, since the devices recognized by the different kernel versions are well documented.

    If, however, you just want to know 'why' something does not work (or does not work after initially working or not-working), feel free to pick any of those four reasons. For example, it's surprising how often I help users who inist their device is MTP-compatible...but actually uses some other method.
    Last edited by Cheesehead; January 1st, 2013 at 10:52 PM.

  7. #7
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    Re: USB / serial converter doesn't show up

    Dargaud,

    Thanks for asking your question, I found a no-name usb -> serial device that I'd like to use, but I couldn't figure out how to identify it.

    I have seen something very much like you describe (works once, not twice) with an SD card reader. One day, instead of "Safely Removing Drive", I used the other option (don't have the menu in front of me) - and I didn't have to reboot when inserting the next card. How are you disconnecting the device on the end of the cable? I think I was unmounting the SD card reader (which was built into the system) each time I attempted to properly remove the card inside it.

  8. #8
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    Re: USB / serial converter doesn't show up

    I saw that my mobo had an internal serial connector, so I used a 2$ bar with a DB9 to get a serial port on the back. Problem solved.

  9. #9
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    Re: USB / serial converter doesn't show up

    I have a device with the Prolific PL2303 chip in it. I am using Ubuntu Studio (Basically Xubuntu), and this is for a Ham radio application. The device doesn't even show up unless I go into a terminal and type lsusb. Looking at the Prolific website, it says there is a driver for Red hat ONLY.

  10. #10
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    Re: USB / serial converter doesn't show up

    Quote Originally Posted by dennisn77-ameritech View Post
    I have a device with the Prolific PL2303 chip in it. I am using Ubuntu Studio (Basically Xubuntu), and this is for a Ham radio application. The device doesn't even show up unless I go into a terminal and type lsusb. Looking at the Prolific website, it says there is a driver for Red hat ONLY.
    Turns out the solution was a simple one. All I had to do was to add my name to the dialout list:

    Go into a terminal:
    sudo adduser dennis (In my case) dialout
    (Hit enter)
    Give password when asked for it.

    Exit the terminal.

    Log out of Linux. Log back in. And you're done.

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