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Thread: Teensy 4.1 turns on LED faintly with no blinking

  1. #1
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    Teensy 4.1 turns on LED faintly with no blinking

    I recently bought a Teensy 4.1 with the pins soldered and when I tried to plug it into a computer running windows with a micro usb cable with data capabilities, it did not recognize it and the LED did not turn on. I measured the voltage in the 5V and 3V pins and got 5V and 3.28V respectively. Power was being supplied but there was no visible output in terms of the connection to the windows device and the LED in the Teensy. I read on the Troubleshoot page that Teensy's tend to have some detection problems on windows so I tried plugging it into a Mac and got the LED to turn on but it was a faint light without any blinking. At the same time, the Mac was not recognizing the Teensy. I did notice that when the micro usb cable was moved or twisted, the LED had a greater intensity to its light. Different micro usb cables were tested yet they all gave the same result. Another Teensy 4.1 with the pins soldered was also tested using the same computer and cable and it worked perfectly. Is this something that is caused by a faulty micro usb port on the Teensy? Some sort of mishandling?

    Thanks in advance!!

  2. #2
    Senior Member PaulStoffregen's Avatar
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    That's a really strange set of problems. Must admit, I'm mystified how the LED could be dim and have its brightness affected by moving the cable, but you measured 3.28 volts.

    Sounds like the board must have been damaged during the pins soldering and the problem not detected by our test after-pin-soldering process, which checks all the soldered pins using a ZIF socket, but doesn't use a USB cable. Or maybe it could have been damaged during shipping. But how any type of damage could cause such a strange result with LED on faint yet full 3.28V power on the 3.3V pin is something I just don't understand.

    I'll ask Robin to contact you. It'll be a couple weeks until we can offer a replacement, as Teensy 4.1 is currently out of stock. A new batch is due in 1 week, but it'll take at least another week for any to have pins soldered.

  3. #3
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    I was puzzled as well with the LED behaving as such, it is a weird one. I appreciate the response and the quickness of it. I'll wait for Robin's message; once again thank you for the response!

  4. #4
    In the mean time, can you perform an operation like analogRead and see if it will display anything? Finger pressing the analog pin, connecting the analog pin to GND or 3v3, type test. Also test digitalRead to see if they work? I wonder if it's just the LED.

  5. #5
    Senior Member BriComp's Avatar
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    Quote Originally Posted by jackway View Post
    I was puzzled as well with the LED behaving as such, it is a weird one. I appreciate the response and the quickness of it. I'll wait for Robin's message; once again thank you for the response!
    If you have not been contacted by now, I would remind them of their promise.
    The T4.1 is in stock now, but low levels of stock. Don't wait until they run out again.

  6. #6
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    Quote Originally Posted by KrisKasprzak View Post
    In the mean time, can you perform an operation like analogRead and see if it will display anything? Finger pressing the analog pin, connecting the analog pin to GND or 3v3, type test. Also test digitalRead to see if they work? I wonder if it's just the LED.
    There is voltage across all the pins but the Teensy is not recognized when plugged into a computer; I'm not able to program anything. How would I perform the analogRead and digitalRead operation?

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