Newbie - how to get stereo audio in?

[edent]

Real newb here. I have a couple of microphone-level analogue audio sources that I want to connect and record.
Is it it just a case of wiring the mic directly into the pins? If so, what do I need to do to record the audio as WAV?
Sorry - couldn’t find a tutorial on this.

[stuartiannaylor]

Audio Support Rock Pi S

Just thought sod it and connected a analogue mic module without dc blocking caps. 3.3 -> Module VCC, GND -> Module GND Out -> Mic-P, GND -> Mic-N Works fine the mems is a bit quiet and the electret with the MAX9814 is mighty as it usually is. There was DC buzz but far less than my lazy approach expected as thought it would be horrendous but ok just to test. I will get some .1uf ceramics on Mic-N & Mic-P and see how its goes. Also while I am at it a 4.7uF DC blockers on the stereo out i…

You can wire yourself if you create the simple circuit to apply the mic bias.
My electronics is extremely rusty but I think the simplest way without module is to apply the vbias as mic-p and return both via approx a 100nf dc blocking cap.

Otherwise use a mic module and from findings in the above use a MAX9814 Microphone Board Module as there seems to be a level of noise on the SoC that if you up the codec gain you also increase noise.
My computer is such a noisy thing that actually quite a proportion was the fan noise of my SSH connected PC.
But the MAX9814 gives a much stronger signal and seems to be much clearer, but have a read of the above.

I2S mics throws everything onto I2S even output which is for many not great.
PDM I have still to check.
Maybe when you wire up just a simple circuit with Mic bias and an electret it produces great results but wasn’t exactly sure so just went with modules.

The strangest thing though for analogue mics is 3,4 is missing so we have 1,2,5,6,7,8 ?! Like WTF or what?
You can also have a listen to a single mic with my dull droning voice on the above post.

I am starting to get a handle on the analogue mics and if you haven’t a mic module you will have to create a little circuit with micbias applied and micp & micn returned via 100nf dc blocking caps with the micbias v ref setting being a single control in alsamixer.

Go to the figure index of https://dl.radxa.com/rockpis/docs/hw/datasheets/Rockchip%20RK3308TRM%20V1.1%20Part1-20180810.pdf and find the microphone input bit.

In alsamixer they used the decimal percent of the 3v3 register to name the micbias voltage which confused me.
ADC_LEVEL_RANGE_MICBIAS
The level range control signal of MICBIAS voltage:
3’b000: 0.5AVDD33
3’b001: 0.55AVDD33
3’b010: 0.6AVDD33
3’b011: 0.65AVDD33
3’b100: 0.7AVDD33
3’b101: 0.75AVDD33
3’b110: 0.8AVDD33
3’b111: 0.85AVDD33
Note: Only the reg (ADC_ANA_CON7+0x0)[2:0] represent the
level range control signal of MICBIAS voltage

But the above should make sense when you look at alsamixer and the bias setting.
The ADC max input is 1.8v peak and think that is +1.8/-1.8 but use the micbias as was wondering where you get the 1.8v level you might need but it already available on micbias.

http://www.learningaboutelectronics.com/Articles/Electret-microphones

I don’t think you need the 1k-10k resistor as micbias is setup and prob current limited and the only change is they recommend 100nf not 10nf dc blocking on both micn & micp with micbias being of what you could say the positive of an electret and gnd on the negative.

Wow long winded and haven’t tried but think that is likely.