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Thread: Powering Teensy 3.6 with 3.3V?

  1. #51
    Senior Member+ defragster's Avatar
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    Quote Originally Posted by gimpo View Post
    Found! Thanks.
    I will give it a try. Unfortunately I will not able to test it until the middle of July, since my motorcycle will be transported to Italy tomorrow...
    Bummer you didn't get to try it before shipping. It might not relate - but if it does the software fix is better than hardware for what it does.

    Glad the file was found - didn't notice Paul's post had file excluding the file's name

  2. #52
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by gimpo View Post
    All of this components basically hold the Reset pin down until the supply voltage reaches the desired level.
    But something is not clear to me: since all of them keep the reset down for a further period of time (typically from 150 to 500 ms) by using a timer, shouldn't they act like the capacitor soldered on the reset pad? I mean, are not they going to inhibits the re-programmability when the USB connector is plugged?
    They come in 2 types. The "push pull" type definitely will cause problems. The "open collector" or "open drain" type is fine, since it doesn't actively drive the pin after it's done holding the line low.

    However, before you try this, make sure you're using Teensyduino 1.46 or later. With the improved startup code, using one of these supervisor parts might not be necessary.

  3. #53
    Senior Member+ Theremingenieur's Avatar
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    For making sure that USB flashing will work, you should minimize the reset delay. If not, you’ll run in similar issues as with the capacitor.

  4. #54
    Member gimpo's Avatar
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    @Paul
    thanks, I will order some of those components with "open drain", and do some tests when I will be back from Italy

    @thereminggenieur
    the minimu reset delay provided from manufacturers is around 150 ms. I think it is too high... Alternativaly, I have to go back to your original idea, i.e. mounting the Voltage regulator that you indicated in place of my Murata OKI.
    I'm just a little bit worry heat dissipation. When flooded with resin the VDO could have some problems. My current absorption is around max 180 mA ( Teensy 3.2 + TFT 1,54" display + High luminosity LED light from Adafruit). ... mmmh...


    - One million dollar question -
    As collateral (positive) effect, could the capacitor on the reset pin provide a good protection from cloning my code?
    After all, if Teensy doesn't start, there are few possibilities that somebody could read the flash memory by simply plugging an USB cable in the USB-port. I'm right?

  5. #55
    Senior Member+ Theremingenieur's Avatar
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    No, the flash can't be read out via USB. One would need to fiddle with some small contacts on the PCB.

  6. #56
    Member gimpo's Avatar
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    Do you mean in any case, or just when the cap is soldered on the reset pad?

  7. #57
    Senior Member+ Theremingenieur's Avatar
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    In any case

  8. #58
    Member gimpo's Avatar
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    So why people struggle in setting the flash security byte???
    (For my needs, preventing my sketch-software from cloning via the USB plug would be enough, since everything, but the USB connector, is flooded with resin.)

    see https://forum.pjrc.com/threads/35333...-security-byte

  9. #59
    Senior Member+ Theremingenieur's Avatar
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    The flash security byte is intended to prevent reading out the flash via JTAG, but as I said above, establishing a JTAG connection is not possible without additional microscopic soldering on the Teensy PCB. It's most times used by people who build their custom Teensy boards where these contacts could be easier to access.

  10. #60
    Member gimpo's Avatar
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    Ok, thanks a lot for the precious information!

  11. #61
    Member gimpo's Avatar
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    On the fly:
    I tried to re-program a Teensy 3.2 via the USB cable after a 0.1 uF capacitor was soldered on the reset pin. The Teensy seems now dead (no led light, no output on the attached TFT display, nothing).
    Somebody had the same experience?
    It is normal?

    (Yes, I know that the capacitor inhibits the re-programmabiliy, I was simply going to test it )

  12. #62
    Senior Member+ defragster's Avatar
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    Did you remove the cap and try again?

    Got a picture? Miswired cap? Polarized cap wrong way?

  13. #63
    Member gimpo's Avatar
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    Yes, I detached/cut completely the cap using small scissors. Nevertheless, the Teensy stays dead, the Arduino IDE say that there is no device attached to the USB cable.
    I'm using a no-polarized cap.

    FYI
    I'm already programmed a dozen of Teensy, then I soldered the cap on everyopne. They are working flawless. I never tried to program a "capacited" Teensy before now.
    So, as I understand, this has not happened to any one. The only explanation is that I've done something wrong while picking up the Teensy from the test-board and soldering...

    I'm strongly tempted to repeat the experiment with a new Teensy.

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