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Thread: Linux ModemManager Strikes Back

  1. #1
    Senior Member PaulStoffregen's Avatar
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    Linux ModemManager Strikes Back

    Looks like ModemManager is again interfering with Teensy on Ubuntu 18.04. Seems Ubuntu recently changed MM's default filter policy to "strict", which causes it to ignore some udev tags.

    I've updated the 49-teensy.rules file with another tag to hopefully keep MM from messing with Teensy.

    https://www.pjrc.com/teensy/49-teensy.rules

    To check which filter policy ModemManager is using, run this command:

    systemctl status ModemManager | grep filter-policy

    If you get nothing, that's a pretty good sign you don't have ModemManager. Running without "| grep filter-policy" can confirm.

  2. #2
    Member ETMoody3's Avatar
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    Well, that's one less unexplained phenomenon to workaround.

    I noticed, I figured it was something low level I did on my system .

  3. #3
    Senior Member PaulStoffregen's Avatar
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    Did the new udev rules fully fix the problems on your machine?

    It seems to work here on my Ubuntu 18.04 system, though I do still seem some stuff in syslog that ModemManager is taking notice of Teensy.

  4. #4
    Member ETMoody3's Avatar
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    Well, I haven't copied the new rules in (yet). Instead I removed ModemManager.

    It was also keeping a USBTinyISP from working correctly.

  5. #5
    Senior Member PaulStoffregen's Avatar
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    Probably a good idea to get the new udev rules anyway. ModemManager always seems to have a way of coming back to cause more trouble.

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