Amazon Echo Dot Gen 3 – Microphone Disable Circuitry

Have you been interested in the Echo Dot device? One feature they mention is that there is a microphone off button. I spent a few hours reverse engineering this, and recorded (in un-edited glory) the process:

The resulting schematic is shown below:

The astute reader will note the only pin under direct control allows the disabling of the microphone, it cannot re-enable it. However – there is one more loophole to check.

The microphone comes up in an “online” state due to the strapping circuit. On quick check, it appears the 3.3V source is coming directly from a main 3.3V regulator which doesn’t seem to be controlled by the microcontroller. But I don’t guarantee there isn’t some way for the microcontroller to turn off the entire power, which if so would cause the microphone to be re-enabled when the device turns back on. It’s the last thing I’ll investigate, but will take some more effort to do so.

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