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I am trying to use this TRRS plug (4 connectors) to send my signal to a smartphone.

When microphone connected directly to the plug, Android on smartphone recognizes it as a headset.
When I disconnect microphone and supply my own PWN signal and ground, Android says it is a headphone.

How can I mimic a microphone connected while supplying my generated signal instead of microphone's?

UPDATE: I've noticed that mic and ground lines have resistance of 1K-1.5K depending on a headset or mic hardware, and I tried to
mimic that by placing 0.8K resistor connecting mic and ground, but still my setup seen as 'Headphones' instead of a headset.
Good question. The SparkFun site is really excellent but it falls really short on hookup documentation for this particular product.

SparkFun folks: (1) why isn’t there a hookup guide for the TRRS module showing some basic and preferred hookup connections between the TRRS and say, an RN-52 for iPhone and Android wired headsets, for example? I know this is basic stuff for your audio engineers.. or a hookup diagram for connecting the TRRS to an IPhone or Android jack for in/out audio at “line” level? People really need these details to use the TRRS breakout properly, especially when a device like the RN-52 needs a config change for the mic input to even work, or people can spend days googling “iPhone mic circuits” (which is a nightmare of confusing advice btw) to figure out what is wrong with their mic circuit (as I did!). It’s also not clear to me (for example) whether MIC_L- is supposed to be wired to the RN-52 ground or not when MIC_BIAS has to be tied to MIC_L+ to power the headset’s mic (how to properly wire Sparkfun’s 3-wire mic interfaces to a 2-wire mic on TRRS pins 3&4, etc.. Must the MIC- be tied to GND on an RN-52 for MIC_BIAS to work? Or is MIC_L/R- the ground line for MIC_BIAS?

(2) I was disappointed to find that the RN-52 doesn’t seem to automatically route a headset mic input to an iPhone by default. It seems to be only setup for speaker audio from the iPhone over Bluetooth, so you must terminal-into the RN-52 and risk damaging it if you miswire just to turn on the mic flow. The RN-52 hookup guide doesn’t seem to explain the proper commands to issue to the RN-52 either to enable the mic input for phone calls etc, AFAIK

Feedback from SparkFun folks would be great thanks!