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Thread: Teensy 3.2/3.6 USB port unresponsive

  1. #1
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    Teensy 3.2/3.6 USB port unresponsive

    Greetings. I have a 3.2 Teensy and a 3.6 Teensy which both worked fine out of the box...and then didn't. The 3.2 is now in a state where, when first connected via USB to a PC, briefly shows a USB device in Device Manager. Then the port disappears after a few seconds. The 3.2 seems OK (its LED flashes in a manner which indicates to me it's OK). The 3.6 Teensy does not appear *at all* in the PC's device manager as a USB port. I suspect it, also, is running just fine...except it can't/won't talk over the USB port.

    Both these boards did, when first rec'd, operate just fine. Has anyone else seen symptoms like this? Any ideas on what might have happened?

    Thanks much.

    bob

  2. #2
    Senior Member PaulStoffregen's Avatar
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    What exactly are you looking for "shows a USB device in Device Manager"?

    When you press the button on your Teensy, the LED should stop blinking (if Teensy is running code that blinks the LED). Teensy should appear as a HID device, not serial.

    https://www.pjrc.com/teensy/check_halfkay_vista.html


  3. #3
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    "Shows a USB device" means that the Ports section of Devcie Manager shows something like the "USB Serial Device" entry in the following:
    Click image for larger version. 

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    If Device Manager does not show such a line, the Arduino IDE will not download code onto the Teensy.

    I have pressed the Teensy button; it does not help.

    My misbehaving Teensy's do *not* result in the HID section of Device Manager showing a HID device with a Hardware ID which includes the string VID_16C0.

    I hope that helps you to understand what I am observing (and not observing).

    Thanks.

    bob

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    Bob, I think you might be still looking at the wrong area. The Ports (COM & LPT) relates to USB Serial. The Teensy programming is done over USB HID.
    When I press the program button on a Teensy 3.2, it shows under Device Manager > Human Interface Devices > USB Input Device.

    Click image for larger version. 

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    Fair enough...except that I cannot program either Teensy device from the IDE, yet both devices seem to come up and run just fine. So it appears the USB link is non-functional in some way. I am wondering if others have seen this behavior before and, even more interesting, what failure modes, or adverse conditions, lead to a behavior where the Teensy (a) won't effectively communicate over the USB yet (b) comes up and runs?

    I am asking because if I understand what caused this, I am, hopefully, better able to prevent this failure mode from occurring in the future.

    Thanks much.

    bob

    PS I have lots of HID devices on my system, yet few Ports...so when a Teensy connects, it's much easier to notice a change in the list-of-Ports than it is to notice a change in the list-of-HIDs. Or might I be missing something? Thanks again!

  6. #6
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by bobobobo View Post
    I am wondering if others have seen this behavior before
    Yes, we have indeed seen this over and over.

    and, even more interesting, what failure modes, or adverse conditions, lead to a behavior where the Teensy (a) won't effectively communicate over the USB yet (b) comes up and runs?
    It's almost always a charge-only cable. These are included with cheap products that charge by USB power, sometimes even low-end phones. They look just like a regular (short) USB cable, but inside the cable has only the 2 power wires. The 2 data wires are completely missing.

    These cables are very common in people's "leftover" cables box or drawer. We've even seen cases people who said they tried 2 or 3 different cables, then all of them turned out to be these charge-only cables they had tossed in a box after buying rechargeable gadgets. When they "borrowed" a known-good cable from some real USB product, or bought a good one from a store, suddenly everything worked. It's come up many times on this forum, pretty much always the same story - people don't believe the 2 or 3 cables they have laying around could all be bad, but the reality is drawers of leftover USB cables are filled with these no-data charging cables that look indistinguishable from real USB cables.

    Bad USB hubs and damage to the USB connector on Teensy are also possible causes, but relatively rare. When Teensy gets power to run, but absolutely no USB communication at all, it's almost always a charge-only cable.

    This problem is so common that on the upcoming Teensy 4.0 we're adding a red LED dedicated to showing you the bootloader status. A special dim blinking mode will indicate when Teensy detects this problem.

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    Paul - thanks for that...quite interesting. But, unfortunately for this discussion not as relevant as one might think. The cable I am using to talk to the "failing" Teensy's is the same cable I am using to speak to "working" Teensy's. In this case, "working" means I can program the Teensy.

    The only nameable suspicion I have as a reason for the failure may be environmental (overheating)...but I don't have a high degree of confidence in this hypothesis. I am hoping this forum can name some other possible suspicions.

    bob

  8. #8
    Senior Member+ defragster's Avatar
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    Generally the USB connect via healthy happy computer to a non-abused Teensy running Valid code over a good cable and USB pathway is 110% reliable and effective.

    What is common with a large number of users is a small subset having this issue appear intermittently or otherwise when one of the above items or post #6 is violated - or the posted trouble shooting sections.

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    defragster - I understand your points well. The key phrase in your post for me is "non-abused Teensy". I suspect my Teensy's were abused in my embedded environment...but I don't know for sure and, if they were, I don't know how. In an effort to reduce the probability that such abuse will occur in the future, I need to understand what form(s) that abuse may have come in; with such an understanding I can work to eliminate such abuse. If other folks have ideas about what may have caused these symptoms, I'd be most happy to hear about their lessons learned, so they can become my lessons learned.

    Cheers and thanks.

    bob

  10. #10
    Senior Member PaulStoffregen's Avatar
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    If the Teensy appears to be still running its program correctly, and you're really sure the USB cable is good, I'd get a magnifier & bright light and visually inspect the USB connector for signs of damage.

  11. #11
    Senior Member+ Frank B's Avatar
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    Quote Originally Posted by bobobobo View Post
    The 3.2 is now in a state where, when first connected via USB to a PC, briefly shows a USB device in Device Manager. Then the port disappears after a few seconds.
    I'd say this clearly means that there is no hardware failure - unless it's a loose connection. The Teensy handles the USB connection in software and at least needs enabled interrupts and other basic things like a valid stackpointer. There is no dedicated chip that does USB. Maybe you have just disabled the interrupts, the Teensy runs a program with USB Settings "No USB", or its software crashes somehow. Have you tried the long button press to delete the flash? Ever tried to upload an other program? Have you disconnected all wires or other hardware from the Teensy?

    OR: A damaged USB Port on your computer or hub. Or a defective Windows installation.
    Last edited by Frank B; 04-02-2019 at 09:05 AM.

  12. #12
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by bobobobo View Post
    If other folks have ideas about what may have caused these symptoms....
    You need to understand we hear these symptoms over and over, and it's almost always a bad USB cable or a misunderstanding about how to check if your PC really is detecting Teensy.

    Many, many times on this forum we've heard someone say pretty much the same things you've said, convinced their Teensy was dead, and then after getting them to actually try things in different ways, suddenly it turned out to start working again.

    So I hope you can understand some of this skepticism you're hearing from us. Your boards may indeed be damaged. Without any info, and apparently *you* don't even know what happened to these boards, nobody here can even begin to guess what may have gone wrong.

    But your main question seems to be asking for our collective knowledge & experience, based on what we've seen from others, rather than asking directly for help by giving us info & context specific to your problem. Please let me tell you in the clearest way possible, the things we see over and over are charge-only cables, misunderstanding how to check for detection of Teensy (Serial vs HID), code & driver issues that prevent automatic upload (but programming still works with the inconvenience of pressing the button on Teensy), and destroyed hardware. I can tell you cases of partial damage to the hardware are rare. Hardware damage is usually all-or-nothing. When something destroys the hardware, it's usually completely dead, often with the chip getting very hot.

    So if your boards are showing some signs of life, but not communicating with your PC, I hope you can understand our perspective & assumptions when you keep asking for our collective knowledge & experience, with scant details on what you're actually trying, with little clarity on what specific problem behavior you're observing.

  13. #13
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    I did perform a bright light/magnifier-glass examination and *voila* there is visible damage to the on-board USB connector. In the future, in our system, we will forego the provided surface-mount USB connector, and use the pads on the Teensy to cobble together a pigtail connector so that there is no physical strain or stress to the board or the on-board USB connector when (dis)connecting a USB cable.

    Thanks...all assistance was most welcome and helpful and happily received.

    bob

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