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Thread: Teensy 4.0 never initiates com port Windows 10

  1. #1
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    Teensy 4.0 never initiates com port Windows 10

    My Teensy 4.0 boards were working for a while, but now they don't show up on a com port.

    I plugged the usb cable into the teensy 4.0
    Nothing happened.
    Then, I pressed the button on the teensy.
    Windows chimed, but I couldn't find any indication in the Device Manager that
    anything happened.
    I went into the Device Manager and uninstalled all of the Universal Serial Bus controllers,
    and then instructed the Device Manager to scan for new hardware.
    No matter what I do, the teensy does not seem to be recognized, and
    it never instantiates a COM port.

    I've tried different Restarting Windows, new USB cables, different ports, but keep having the same results. ...and of course I tried multiple brands and models of boards are recognized instantly.

  2. #2
    Senior Member+ KurtE's Avatar
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    Things to try.

    Plug in the T4 with a cable... Hold down the program button for about 10+ seconds and the program light should come on dimly sort of blink... Then release. You should then see program LED stay on for a bit. It is reprogramming the teensy with the default blink program that it was originally shipped with.

    You should then be able to load up a program in Arduino IDE with the right board type selected and USB Type= Serial and do a verify command which should build it (I often use the simple blink program for this) which should then load up the Teensy program. Once that is up press the program button on the Teensy and hopefully you will see that the Teensy program sees it and programs it with the program you just did a verify on....

  3. #3
    Senior Member+ mjs513's Avatar
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    If its a brand new Teensy it may not show up in the Windows COM manager. On first connect it shows as a HID device in the Arduino IDE until you upload your first sketch. What does it show as the Port in the Arduino IDE?

  4. #4
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by LEDLI! View Post
    Windows chimed, but I couldn't find any indication in the Device Manager that
    ......
    it never instantiates a COM port.
    You're looking in the wrong place! Teensy uses HID protocol in bootloader mode, not serial. So it is supposed to appear under "Human Interface Devices". If you look only in "Ports" you'll never see it and believe the USB isn't working, because it's not supposed to appear there and it's not supposed to be a COM port!

    Well, not until it's successfully running a program you've uploaded, and only if you had Tools > USB Type set to Serial (or any of the options which have Serial). Only then does it become a serial device where Windows creates a COM port.

  5. #5
    Senior Member PaulStoffregen's Avatar
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    While troubleshooting, I recommend keeping the small Teensy Loader window visible on your screen. Turn off "Auto" mode, so it doesn't immediately reprogram your board. That way you can use it to immediate see if your Teensy has been detected in bootloader mode.

    If things are really going badly, you could try the 15 second button press which does a full wipe of the flash memory and writes a known-good (RawHID, not serial) LED blink program back into the memory. Hold the pushbutton for about 15 seconds. When you see the quick flash on the red LED, release the button. You'll see the red LED on bright for about half a minute while it wipes the flash and writes the LED blink. Then it'll reboot, where the red LED turns off and you'll see the orange LED blinkly slowly.

    Again, that HID protocol, not Serial. Look for it in Human Interface Devices in the Windows Device Manager, or in the Arduino IDE with Teensyduino installed, click the Tools > Ports menu. You'll see it's detected in that menu as a HID interface which has ID numbers rather than a COM port.

  6. #6
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    Thank you for all the info about what is going on when interfacing with the Teensy 4.0. I got it all working again now. Thank you very much.

    Today I will be receiving my SmartMatrix SmartLED Shield for Teensy 4 and 64 x 32 RGB LED Matrix. I'm excited to get started learning that.
    Is there a definitive site link with in depth tutorials etc.?

  7. #7
    Senior Member+ MichaelMeissner's Avatar
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    There is the pixelmatrix/smartmatrix/smartled site


    Here are some things that I posted in bringing up my display:
    • Evidently the original Teensy 4.0 that I attached had some issues with my soldering. I put another Teensy 4.0 on and it was fine, once I attached it correctly.
    • Originally, I was attaching the Teensy underneath the Smartled shield, instead of on top of it. It took me awhile to realize the pictures showed this orientation. On my large monitor (3440x1440) the posted pictures are just too small to see in detail how to attach it.
    • In addition, it took me awhile to realize that when I was using the 2x8 cable, I needed to connect it from the top and not from the bottom (otherwise I would connect the wrong rows). Yes it is in the documentation, but I evidently missed it.
    • Note, with the 4mm pitch 64x32 display I bought from Adafruit, the Smartled shield will not attach directly to the 2x8 pins, and I had to use the 2x8 cable to attach the display to the shield (and get the orientation wrong). The 3mm pitch 64x32 display fits directly on the shield.
    • I discovered in using the 3mm pitch 64x32 display, that I have 2 red LEDs that don’t display.


    Some other things:
    • There is a 4 pin cable meant for hooking up APA102/DOTSTAR leds. Smartmatrix says you can use this to power the display. I found this cable does not provide enough power, and I eventually just unsoldered the cable. Instead, I hacked up one of the Adafruit power cables, and made two pins to connect to VIN and Ground. I find a 64x32 display screen from Adafruit tends to use about 1 amp of power at 5v, so you might need to add more power if you are using a computer USB to program it.
    • If you use a Teensy 4.1, as Smartmatrix says, you probably want to clip off the back 10 pins in each row. I used 24 pin stacking headers and just clipped off the back pins. You will also need to remove one of the mounting tabs to allow the 4.1 to be mounted.
    • Note the pins for the first SPI bus are used by the Smartmatrix shield for Teensy 4.x.
    Last edited by MichaelMeissner; 02-12-2021 at 03:58 PM.

  8. #8
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    Cool! Thanks for the Smartmatrix link and info. I am pouring over it right now. Thank you so much!

  9. #9
    Quote Originally Posted by MichaelMeissner View Post
    There is a 4 pin cable meant for hooking up APA102/DOTSTAR leds. Smartmatrix says you can use this to power the display. I found this cable does not provide enough power, and I eventually just unsoldered the cable.
    The 4 pin cable can't provide power to the LED matrix because the 2x8 pin interface doesn't pass any power connections between the shield and the matrix, only data signals. The 4 pin cable can be used to power the shield and the Teensy if you are not connecting a USB cable.

    The LED matrix gets power from a separate power connector on the back of the matrix, and should come with power cables. Ideally, you would connect this to a separate 5V power supply like this one: https://www.sparkfun.com/products/16607

    I wouldn't recommend hacking the power cables to connect them directly to the Teensy since that might overload your USB port.

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