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Thread: Teensy 4.1 Breakout -- Power and USB question

  1. #1

    Teensy 4.1 Breakout -- Power and USB question

    Hi all,

    I'm building a synth with a Teensy 4.1 and have a question about power and USB. I'd like to have my breakout board feature an external USB B connector where I can program and get send/receive midi from the Teensy (like this one) and to also feed the Teensy 5V from a 7805 regulator circuit.

    My plan:

    1. Cut the VIN/VUSB trace on the Teensy.
    2. Connect the GND and Vin pins to 0 and +5V from the regulator circuit.
    3. Connect the USB B connector to the USB host pins in the middle of the Teensy

    Will this setup work? Also, if I leave the USB Host 5V pin disconnected from the USB B connector, do I even need to cut the trace?

    Thanks so much for any feedback.

  2. #2
    Senior Member
    Join Date
    Dec 2016
    Montreal, Canada
    yes the trace cut is equivalent to removing the power wire from the USB cord. using a powerless usb cable has benefit that you can reprogram teensy with (powerless cable) or without (powered usb cable) external power source but you'll need to remember to use that cable and no other. you can also use diodes so you can use any or both power sources together, it's somewhere on this forum

  3. #3
    Senior Member
    Join Date
    Jul 2014
    Quote Originally Posted by toutant View Post
    3. Connect the USB B connector to the USB host pins in the middle of the Teensy
    You cannot program Teensy via USB host pins.

    To use USB host pins as USB device (e.e. for Seria, MIDI etc) you have to write your own USB device SW for USB2 (the one accessible via USB host pins)

    To use access USB1 (USB connector) you can either prepare a power less cable, or use the two tiny dots below the USB connector.

  4. #4
    Oh, ok. So the host pins are for powering and communicating with external "devices" plugged into the teensy. Thanks for the explanation WMXZ.

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