Oh I love this. Quick implementation idea. First use a boost converter to bring the 3.3V up as much as possible than an H-bridge type switcher into a diode -capacitor voltage multiplier. The H-bridge switch would need a clock, let's use SCL for that. First the Add-on sits there doing nothing until the badge tries to talk to it, which starts building up the voltage until it is high enough to feed it into the GPIOs.
Oh I love this. Quick implementation idea. First use a boost converter to bring the 3.3V up as much as possible than an H-bridge type switcher into a diode -capacitor voltage multiplier. The H-bridge switch would need a clock, let's use SCL for that. First the Add-on sits there doing nothing until the badge tries to talk to it, which starts building up the voltage until it is high enough to feed it into the GPIOs.
#not_a_badge