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Thread: The /dev/cu.usbmodem440323 port name Teensys appear with - how static is it?

  1. #1

    The /dev/cu.usbmodem440323 port name Teensys appear with - how static is it?

    Mac OS X (but may be similar with Linux I'm guessing?):

    I've got this notion from way back - I'm sure when titting about with lots of simultaneously connected Arduinos and FTDI serial boards that the number on the end of their serial port path name wasn't necessarily the same every time I plugged one in. Sometimes I'd wake up the computer and a couple of the FTDI boards had swapped their names.

    But the Teensys seem to hold on to theirs - is that just random luck (that I shouldn't rely on) or do they work differently - ie will the Teensy in front of me always show up as /dev/cu.usbmodem880591? It'd be bloody handy if I could use that instead of having to identify them programmatically...

  2. #2
    Senior Member
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    The port name is based upon the Teensy's serial number.

    See here for more info:

    Serial Numbers, MAC, and device name on MacOSX

    Duplicate usb modem number HELP!

  3. #3
    Ahh, cool - thanks!

  4. #4
    Senior Member PaulStoffregen's Avatar
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    Yup, that particular Teensy should always appear as exactly that device name.

    Well, of course if Apple doesn't make changes in OS-X. See the old messages about the bug in their driver. If they ever fix that bug, an extra zero may appear in the name, because we're adding a zero to work around that OS-X bug.

  5. #5
    Senior Member PaulStoffregen's Avatar
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    I should also mention this advise only applies to 32 bit Teensy boards. Only the newer 32 bit boards have permanent, unique serial numbers.

    The older 8 bit AVR boards use a fixed serial number. If you connect 2 or more at once, all but the first one get random names assigned.

  6. #6
    Thanks Paul - that makes things a lot clearer

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