Teensy 3.1 + FastLED with USB and external power

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julian

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Hi there,

I'm running into problems when I control a bunch of APA102 LEDs with the FastLED library and have external power and usb connected. It runs smoothly without the USB and stops animating when I connect USB. Of course I have cut the connection between VUSB and 5V apart (as described here https://www.pjrc.com/teensy/external_power.html) but that didn't help. Also tried with a modified USB cable. Still no luck.

Any ideas what the problem might be?

Thanks!

Julian
 
Is the circuit running from an isolated AC/DC power supply? If yes it might be that plugging in USB will suddenly give it a reference to earth potential, resulting in electrostatic discharge.
 
I'm using an ac/dc power supply which is grounded and plugged into the same socket as the computer.
The problem also occurs when I use my laptop in battery mode instead of the computer.
 
Ah, great, thanks.
I ended up flashing the teensy from my Macbook (probably with a slightly different version of the library) and I didn't get this problem anymore. Reading through the issue on Github, this now makes total sense.
 
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