Power to boron / xenon

To supply power to a boron / xenon should I :

  • connect 5v to VUSB
  • ground EN
    Then to plug the usb in and debug :
  • disconnect VUSB
  • disconnect EN

With the electrons I supply 5v to VIN so I may be overthinking this but I don’t want to fry anything.

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Unlike the Electron/Photon on mesh devices there is no protection diode between the USB connector and VUSB.
So when supplying power both ways you need to be extra careful (others even suggest to keep it mutually exclusive) but grounding EN does not mitigate the potential danger for your USB port in case of back-feeding via VUSB in any way.

What you can do is to manufacture a custom USB cable which disconnects the USB Vcc line.
I’ve 3D printed myself a little insulator inlay for the USB-A connector, but you could just cut the red wire or splice in a Schottky diode to mimic the protection diode on the Electron.

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I built these boards to make it easy to disconnect USB power to make it easy to use the USB debug serial at the same time as external power on VUSB.

Just two USB connectors, a switch, LED, and resistor.


Thanks guys, good info there.

I’ll cut the power wire on one of the usb cables, supply 5V to VUSB and leave EN floating.

Just wondering, rikkas7 is there a reason you used a switch and not a diode in your circuit?