Bluetooth module XS3868 audio IN issue (Mic Input)

Hi There!
I design a small board to receive and transmit audio as a portable module using the XS3868 module.
About play audio on it no problem. About getting the UART port to change parameters no problem too.

But the mic input is another history, I want to set a line input not a microphone input, it's a minor difference between them basically the input impedance.

So I connect a load resistor from the mic input to GND and connect a .1uF cap to decouple any voltage from the 3868 or from the device connected.

But when I do this, the MIC input from the module set to MUTE. I need to set down the input impedance to minimize noise but is impossible. If i do not use this load resistor the noise in the mic input is increible all the PWM from the module goes directly to the mic input.

Using the recommended configuration for power the module is a mess, appear ripple noise in every VCC/1.8V line at the module. To fix this I set few more capacitors in the internal LDO lines and almost in VCC lines the ripple downs a lot.

So I try all the tips&tricks I know but remains in the same way. All them, potentiometers,decoupling, biasing the input, voltage dividers etc etc.

I don't have all the documents about 3868 configuration variables, I don't know but maybe the chipset can set ON/OFF the mic preamplifier/compressor or audio parameters via program variables.

So, someone play with this input? Some voltage divider or some I'm missing?

Best Regards!

That doesn’t sound right to me. A microphone typically outputs a few millivolts where as a line input is typically a 1V peak to peak signal. Therefore I suspect you will need an amplifier.

Can you post a schematic of what you are trying, and post links to any boards you are using.

Do you mean output impedance?

If the voltage is correct you will need an amplifier with a voltage gain of 1, and a higher current t gain to match the impedance.

Yes, it is something about the chipset itself. Because it is designed to be used with an electret microphone, the input impedance is very high. And because it's used as a hands-free audio device, I'm thinking the internal preamp has an audio compressor too, so the dynamic input voltage range is huge.

I'm thinking that some register from the configuration profile must set a lot of input parameters.

So until I don't set-off the compressor is no way that this works as a line input

About hardware setup I test this 3 ways

First setup, give me a lot of input noise
The second one mutes the mic input
The third is give me some results but the noise is there too

The ripple noise looks like is in the GND at itself, looks like the input is a differential input and do not use GND as signal ground

Thanks, but I was expecting a schematic of the whole project. Arduino Bluetooth module microphone and any microphone amplifier. Along with any switches
you have attached.

I am still not clear what you have.
You seem to have both he line input and the mike input.
What is the line input connected to?
Depending on the signal direction some of those attenuators could be wrong.

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