Back in my day, you could usually sip a few mA from a USB2 port without any trouble.
When I try that now, Windows pops up with a “device not recognized” error. I know you can draw up to 150mA before enumeration, but it looks like after some time, Windows will complain that you haven’t enumerated yet.
Is there an easy way to keep from getting this error without having to actually make the device smart?
I’m hoping for something dumb along the lines of USB-PD but facing the other direction. For the record, it has to work on a USB-A port, so USB-C hacks won’t work.
If the computer has a PS/2 port that you aren’t using, you could probably power the device by plugging it into a passive USB adapter like the ones that came with older keyboards and mice.