I want to connect line-out of a device to the microphone input of an Android phone, a Xiaomi Mi 4X. Then I can record and live stream from the phone.
If I simply connect line-out left/right (red/white) to the sleeve and ground (yellow) to ring 2, then the microphone does work. However, the phone will still use the internal microphone in addition. This does not happen when I use a headset (Bose QC25). So apparently additional wiring is necessary, but how?
I also tried connecting the (unused) headphone connectors to ground, using a 220 Ω resistor. These are ring 2 and the tip. The idea is to match the 32–300 Ω impedance in the Android 3.5 mm Headset Jack Device Specification, hoping that this will make my adapter be recognized as a regular headset. It did not help.