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Thread: HELP - I have two Teensy's with same COM Port Number

  1. #1
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    HELP - I have two Teensy's with same COM Port Number

    I have a weird issue with my Teensy's 3.6. I have two different boards and when I plug the first board to the PC; it will show COM Port 20; if I unplug the first board to plug the second board; then the second board will show as COM Port 20 too (same as the first board). Also, the serial numbers are the same too!

    I haven't plug both boards at the same time. Any help will be appreciated.

  2. #2
    Senior Member+ defragster's Avatar
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    Have either or both been programmed with a sketch from new? A sketch with USB Serial active? Even Blink?

    If the IDE and TeensyLoader are used to install even a blink sketch with USB Serial they should properly report and be recognized.

  3. #3
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    They are recognized. Both boards have been programmed with a sketch without any issues. The only issue I have is that both have the same com port & serial numbers. In theory, they should be unique (each one with different com ports)

  4. #4
    Senior Member PaulStoffregen's Avatar
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    Where did you buy these Teensy 3.6 boards?

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    I bought them from you directly. I bought a couple of the MKL02 from your store to create my own teensy 3.6

  6. #6
    Senior Member+ defragster's Avatar
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    Quote Originally Posted by mendez View Post
    They are recognized. Both boards have been programmed with a sketch without any issues. The only issue I have is that both have the same com port & serial numbers. In theory, they should be unique (each one with different com ports)
    Interesting - that is quite right - they should be unique once they are ID'D. PJRC has process in place to assign unique Serial #'s.

    Not seen this before on Windows - don't know OS in use? IDE and Teensyduino version ?

    Some code could print the serial # from within a sketch (forum has links or steal it from the PJRC core). Looked the other day and TeensyLoader Verbose doesn't seem to expose a device Serial#.

    With TyCommander (search Forum) installed it will present a UI with info about the COM port and Serial#

    Perhaps another computer or rebooting this one.

    One other thing might be to try the eat-3.6's 15 second Restore in turn plug each in start a timer with running second count: Hold Program button as 15 seconds pass and release. If anything unsettled the Teensy that will put the chip back to proper factory state - except there will not be any active sketch - and no USB presentation to PC - until reprogrammed.

  7. #7
    Senior Member+ defragster's Avatar
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    Quote Originally Posted by mendez View Post
    I bought them from you directly. I bought a couple of the MKL02 from your store to create my own teensy 3.6
    This cross-posted while sleeping on the last post. Any self made will not have a unique Serial # until burned into the MCU area. Mixing and matching may confuse the PC.

  8. #8
    Senior Member PaulStoffregen's Avatar
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    Yup, custom made boards will have a blank serial number (all 1s) in the MK66's "program once" memory. Easiest thing to do is edit usb_desc.c and put your own number into the code.

    The serial number is *NOT* stored in the MKL02 chip.

    Windows uses the serial number the distinguish between physical hardware and associate the COM port number.

  9. #9
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    Quote Originally Posted by PaulStoffregen View Post
    Yup, custom made boards will have a blank serial number (all 1s) in the MK66's "program once" memory. Easiest thing to do is edit usb_desc.c and put your own number into the code.

    The serial number is *NOT* stored in the MKL02 chip.

    Windows uses the serial number the distinguish between physical hardware and associate the COM port number.
    Oh OK, makes sense! Thanks. So, is there a way to assign a unique serial number automatically for mass produced boards? Or do I need to edit usb_desc.c each time I load a firmware to the board?
    I will look into editing usb_desc.c

    Thanks again!

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