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Thread: Teensy 4.0 Suddenly Stops Working?

  1. #26
    Senior Member+ mjs513's Avatar
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    Quote Originally Posted by Epartsman View Post
    I can try what you suggested with a different power source. I'm not sure if it will make a difference.

    Yes, still gets very hot when plugged into USB.
    Probably not since its still getting hot. Did you measure voltages on the 5v pin? or the 3.3v pin.

  2. #27
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    Okay,

    This is a good question, and results are listed below...

    All of my prior voltage reports have been measuring between the GND and 3.3V pins on the opposite end of the Teensy board from the USB connector.

    When I measure the 3.3V at that location I get only a fraction of a volt (~0.5V). One of the questions was measuring the resistance on the 3.3V supply. I measured the resistance at that same location and have 6.1 Ohms. I'm told this is too low.

    Now, there are also pins labeled 5V and 3.3V pin near the USB connector. Are the 3.3V pin near the USB connector and the 3.3V pin at the opposite end of the Teensy board the same, or are they different?

    Regardless, the results:

    5V = 4.9V
    3.3V near the USB = ~ 0.5V
    3.3V opposite the USB near the push button = ~ 0.5V

  3. #28
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    So as said before, there is a short circuit between 3.3V and GND. Both 3.3V pins belong to the same rail, there is no difference except for position on the board.
    As said before, if the CPU has ever seen 5V, it could be the short circuit itself.
    At your own risk:
    You could try so desolder and take out the TLV75733P and see if an external 3.3V power supply can drive the board. But I suspect this won't lead to a result other than heating the CPU. Or you could just connect a really powerful 3.3V supply and see which part of the ciruit burns off But as it is broken anyway, it could be a bit of fun experiment. "Who let the smoke out?" "who, who, who, who, who?"
    Anyway, all at your own risk!

  4. #29
    Senior Member PaulStoffregen's Avatar
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    Everything you've said sounds like a wire connected to one of Teensy's pins, or the 3.3V power, accidentally touched 5V power.

    I see you posted photos in msg #8. In msg #3 you said "it looks just like the board photos shown throughout the tutorials". But your photo looks nothing like the tutorials, where the Teensy has pins soldered and it's placed into a solderless breadboard. The photos on msg #8 show a Teensy 4.0 without pins, with all pins in pristine unsoldered condition.

    My best guess is you were attempting to do the tutorials with clip leads and loose parts, rather than using a solderless breadboard. While that can work, and from everything you've said it was working until you got to tutorial #3, with clip leads and loose parts all the materials are so light weight and move so easily when you pull on any wire or the USB cable. It's a recipe for wires and parts accidentally touching each other or other places on the Teensy.

    The damage to your Teensy 4.0 is consistent with a pin or 3.3V accidentally touching the 5V power on VIN and VUSB. The pins are not 5V tolerant. Touching them to the 5V power accidentally, even for just a fraction of a second, destroys the main chip.

    From the tone of every message you've written, it seems you do not believe you could have made this mistake. But if you really were doing those tutorials using loose parts connected to the Teensy by clip leads, even if you used extremely careful measures like securing every wire to the table with tape, the odds of any of those clip leads accidentally touching the wrong place is very high.

    The bad news here is measuring 0.5V on the 3.3V line while nothing else is connected to Teensy means your hardware got damaged. We've seen this before many times. As Frank said (yes, somewhat abruptly) it doesn't happen spontaneously for no reason. This damange happens when pins or 3.3V power are shorted to 5V or higher power supplies, or negative voltage is applied (rare - but it happens sometimes when people do audio projects with opamps using positive and negative power supples).

    I understand it's painful, and expensive, to have this sort of thing happen. But at this point, the only viable path is to replace the Teensy. If you do buy another one, please consider getting it with the pins already soldered (unless you have a soldering iron and good soldering skill) and get the solderless breadboard. The breadboard is solid and relatively heavy, so it doesn't move and flop around like clip leads connected to loose parts. It also holds all the parts in place, so if you do move the cable or accidentally move it around, all the parts move together. The odds of wires accidentally shorting to unintended places is greatly reduced... not as good as a printed circuit board or other hard soldered construction, but solderless breadboard construction is a very reliable way to prototype circuits. Please, do yourself a favor and use a solderless breadboard on your next attempt. I'm sure it will work out much better for you.

  5. #30
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    I don't know if I'll get a second chance with the Teensy. My guess is that I'll be instructed to find a different solution.

    Maybe it was poor judgement to select a "new-to-us" board hoping I could get up to speed quickly. Most of our other hardware debuggers have several additional zeros in their price.

    But, I was asked to find a quick and inexpensive way to retrieve data from a part serially the Teensy looked like the right solution.

    A sincere thank you goes out to all of those who helped me trouble shoot this board.

    Best,

  6. #31
    Senior Member+ defragster's Avatar
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    Bummer on the loss of the Teensy 4.0 before it could show how cool and easy to work with it is! Before PJRC even announces release plans for any new board - he has a test jig built to run every new Teensy and all of it pins and power segments through its paces. And no Teensy is packaged without passing that hardware test - leaving the factory with Blink code.

    For the expense of just one added zero on the price you could get 4 more two work with - three if you count shipping - and still be ahead by a couple of hundred bucks if they can serve the needed purposes.

    Desktop here is not electronics friendly and I've managed to not electrically zap any yet - including a few Beta units and many more - but I know it only takes one 'brushing contact' in the wrong place to over excite the wrong part.

  7. #32
    I purchased over 10 Teensy 4.0 units, and 2 of them stopped working -- I'm not 100% sure why except the common cause was that I was holding the Teensy protoboard while it was powered. No carpets here, just bare floor.

    I think it may have been ESD damage caused by touching the Teensy while it was running. There must be some two points on the 4.0 board where even a slighty sweaty finger essentially shorts it out -- my theory. Like shorting a 5V-6V to a 3.3V pin with just your finger, the salt in sweat gives enough conductivity. Especially if your USB port is sending a slightly higher voltage and you're handling the baby with bare hands, while LIVE. Bad hobbyist habit!

    The Version 3.2 units weren't this sensitive -- none of my 3.0 or 3.2 failed with touching all over the Teensy while it was running. Even the ones I was still using at the same time as the 4.0 on exactly the same circuit design!

    I have since changed my electronics procedure to ground myself and avoid accidental ESD incidents. I have also changed my procedure to never be holding any circuit traces of the Teensy while I plug the USB cable in.

    However, it would be nice if a newer revision of Teensy 4.0 was made slightly less ESD-sensitive and more "hobbyist-proof"

    Press the RESET button carefully, not touching any metal contacts while pressing RESET. There seems to also be a 5V contact and a 3.3V-only contact within the diameter of my finger hovering over a RESET button. Most of the time, fingers is high enough resistance but I guess it isn't always, given the random molecules that are on different human's fingers (like salt and other incidential compounds). I don't know if this was the cause either, might have been something else.

    These are amazing devices and worth it; just be more wary of what seems much higher sensitivity to ESD damage.

    Practice ESD procedures like you practice your COVID-19 procedures! That solved my problem.

    You will have the same ESD issue with more expensive prototype boards too -- 5V intolerant pins -- so be careful of them. Better to gamble with Teensy 4.0 but if you want more bare-handability freedom, and immunity to 5V-3.3V 'accidents', go with the models with 5V-tolerant pins. The nice thing is you can swap a 3.2 with a 4.0 once you've debugged your software and such, the same code runs on both! Just much faster on the new.

    If you want 5V tolerance, get the slower Teensy. I've never had a single failure upon manhandling the boards with bare hands.
    Last edited by GDouglas; 03-12-2020 at 12:53 AM.

  8. #33
    Senior Member+ defragster's Avatar
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    Quote Originally Posted by GDouglas View Post
    I purchased over 10 Teensy 4.0 units, and 2 of them stopped working -- I'm not 100% sure why except the common cause was that I was holding the Teensy protoboard while it was powered. No carpets here, just bare floor.

    I think it may have been ESD damage caused by touching the Teensy while it was running. There must be some two points on the 4.0 board where even a slighty sweaty finger essentially shorts it out -- my theory. Bad hobbyist habit!

    The Version 3.2 units weren't this sensitive -- none of my 3.0 or 3.2 failed with touching all over the Teensy while it was running. Even the ones I was still using at the same time as the 4.0 on exactly the same circuit design!

    I have since changed my electronics procedure to ground myself and avoid accidental ESD incidents. I have also changed my procedure to never be holding any circuit traces of the Teensy while I plug the USB cable in.

    However, it would be nice if a newer revision of Teensy 4.0 was made slightly less ESD-sensitive and more "hobbyist-proof"

    These are amazing devices and worth it; just be more wary of what seems much higher sensitivity to ESD damage.

    Practice ESD procedures like you practice your COVID-19 procedures!
    They seem fairly robust. I have been poorly handling Teensy's for 5 years and not killed one yet. I try to remember to touch the USB hood or other proper ground - especially here in winter in my dry woodstove room - but have caused at least one Teensy reset in the past week handling a Teensy on a USB cable. Also manually grabbing them and exposed pins is common. Sometimes a reset or perhaps a hang - but no damage or failure after restarting.

    Cat gets zapped all the time - and they tend to be wary - funny a minor cat zap the yesterday was echoed on a nearby AM radio.

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