Having trouble building a working Puck.js image

Fri 2018.09.28

Hello @rmd6502, it appears we may be dealing with two issues, so let's remove a bit of confusion.

re: 'I'm powering it from a 3.3v supply off USB'

I'm taking this literally here, but don't wan't to guess. Is there a separate power supply or battery pack being fed by the USB port? (e.g. step down converter)

https://en.wikipedia.org/wiki/USB_3.0

"As with earlier versions of USB, USB 3.0 provides power at 5 volts nominal."

If not, that magic smoke you mentioned might not have any magic in it at all. If this is the case, would you mind posting an image of your wiring so we may take a look. Frayed wire end, solder blob, mis-placed wire, etc. I agree with @Gordon that there shouldn't be any heat felt whatsoever.

Have you tried just a CR2032 and compared heat dissipation with that?

Let's resolve the power supply part first, then others may be able to help with the firmware part.