Hector Martin

Someone claimed that the slider mute switches on Google Home products are software-driven on HN with zero evidence, so I checked. At least on the Home Mini it's hardware. (Also, if you make hard claims on the internet with zero evidence, you're an asshole).

AFAICT the mics are TDM mics in a stereo config (shared data line, idling at average of ~1/2 Vcc, don't have scope with me to check). That's connected to a single AND gate (SN74LV1T00 or equiv), the other input comes from the mute switch.

When the mute is engaged, the output of the gate drops to 0V, and that is what goes to the SoC (after a divider, the SoC is probably 1.8V logic while the mics/AND are at 3.3V).

I traced the path from the hardware switch, through a filter/debounce network, to the AND gate, and from the mics to the AND gate. So unless there are backdoor buried traces that bypass this (which would be hard evidence of a backdoor, since they would make *no sense*), it's safe

Does the SoC have other sensors that can be used as mics, though?