[damip]

What are the killswitches acting on ? Are they acting only on the dedicated "enable" or "poweroff" inputs of various chips ? Are they cutting the power supply of the chips ? Are they cutting both the power and logic busses, thus isolating the target chips (at least electrically) ?

[hawski]

From https://wiki.pine64.org/index.php/PinePhone_FAQ#What_are_the...

  1  Modem | Pulls Q1501 gate up (FET killing modem power) | "On" enables 2G/3G/4G communication and GNSS hardware, "off" disables it.
  2  WiFi / Bluetooth | Pulls up CHIP_EN | "On" enables WiFi and Bluetooth communication hardware, "off" disables it.
  3  Microphone | Breaks microphone bias voltage from the SoC | "On" enables audio input from on-board microphones (not 3.5mm jack), "off" disables it.
  4  Rear camera | Pulls up PWDN on OV5640 | "On" enables the rear camera, "off" disables it.
  5  Front camera | Pulls up PWDN on GC2145 | "On" enables the front camera, "off" disables it.
  6  Headphone | Pulls up IN2 on analog switch BCT4717ETB | "On" enables audio input and output via the 3.5mm audio jack, "off" switches the jack to hardware UART mode.

[KMag]

With the microphone bias floating, what prevents some digital signal processing form recovering faint and fuzzy audio? I'm sure the microphone loses at least several dB of gain with the bias floating, but isn't it much safer to either disconnect the bias and tie it to ground, or else pull up/down the the digital output of the ADC?

I understand that with the bias floating, the microphone output will be a combination of radio and quantum thermal noise, but won't that noise still be slightly modulated by the microphone? Or is it that the noise being modulated will be below detectable by the ADC and the digital output will always be exactly 0?

[yetihehe]

Depends on actual hardware implementation, but those microphones are REALLY good at picking up audio. I once fiddled with some microphone and wondered why it works so poorly (lots of "digital" noise, faint audio), maybe cable broke or smth. Turned ot, it was "disabled" with hardware switch on cable, yet still picked up enough sound to "somewhat work".

[fsflover]

One can check the schematics: http://files.pine64.org/doc/PinePhone/PinePhone%20v1.2a%20Re...