Forum Rule: Always post complete source code & details to reproduce any issue!
Results 1 to 5 of 5

Thread: Does Teensy 3.2 Micro USB need to be Connected to Vin?

  1. #1

    Does Teensy 3.2 Micro USB need to be Connected to Vin?

    Hello,

    I am trying to rebuild the teensy 3.2, but my final project will use an external power source that is not my laptop powering the device. In order to prevent current flowing back into my computer while programming, I know one method is to cut the solder jumper and sever the connection between the micro USB and Vin. However, after VBUS is routed through the fuse could I also just connect the fuse to ground and then not include the solder jumper at all in my design? Or would that cause some other issue.

    I have included a photo of my schematic as it is currently and then what it would look like after I disconnected VBUS from VIN.



    Click image for larger version. 

Name:	PJRC Forum Screenshot1.jpg 
Views:	46 
Size:	79.2 KB 
ID:	24835


    Click image for larger version. 

Name:	PJRC Forum Screenshot 2.jpg 
Views:	23 
Size:	80.5 KB 
ID:	24836

  2. #2
    Senior Member PaulS's Avatar
    Join Date
    Apr 2015
    Location
    Netherlands
    Posts
    659
    If you connect the fuse to GND as in screenshot #2, you effectively short the USB power [VBUS] to ground, which will trip fuse F1 [or the fuse at the laptop side on the VBUS, whichever one is faster to trip].
    Why don't you just omit fuse F1 at all? Or am I misunderstanding you?

    Paulk

  3. #3
    Paul,

    Thank you for the response! I think you are understanding my situation correctly. So you are saying that I should take the fuse out and just connect VBUS directly to GND? I have included a screenshot of what this would look like below. Also, sorry for the quality of the screenshots. The quality looks much better if you click on the image and view it full screen.

    Thank you,
    Maxwell Click image for larger version. 

Name:	PJRC Forum Screenshot 3.jpg 
Views:	43 
Size:	72.8 KB 
ID:	24862

  4. #4
    Senior Member PaulS's Avatar
    Join Date
    Apr 2015
    Location
    Netherlands
    Posts
    659
    "So you are saying that I should take the fuse out": Yes.
    "and just connect VBUS directly to GND?" No. Because that will short the VBUS from your laptop. Just leave VBUS unconnected.

    Since you will be powering your circuit by an external power source, but still want to program your Teensy-like board over USB, this is the way to go:
    Click image for larger version. 

Name:	PJRC Forum Screenshot 4.jpg 
Views:	22 
Size:	105.9 KB 
ID:	24866

    [i'm still not sure whether I understand you correctly...]

    Paul

  5. #5
    Senior Member
    Join Date
    Jul 2014
    Posts
    3,318
    For USB to work you need D+,D-,GND.
    So let VBUS simply open. It has no impact on PC or data transfer.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •