While reviewing the schematic of the STM32MP157 EVAL development board, I came up with the following questions:
I apologize in advance if the translation isn’t perfectly accurate as I used a translator.
The Line Out JACK (CN4) outputs via coupling capacitors from SPKOUTLP (A2, B3). Why are the Line Out pins (B5, B4) not used instead?
The codec supports differential audio output, but why is the negative pin not connected? (Wouldn’t it prevent distortion if the signal is converted to single-ended using an op-amp before connecting to the audio jack?)
Why are the Speaker Out pins used instead of the Line Out pins? (Is it because of the built-in amplifier, or is there another specific reason?)
I have some additional questions regarding the microphone circuit. (Sorry if these are silly questions!)
If I am using a digital microphone (IMP34DT05TR), can I apply a different power supply (3.3V) to the microphone module instead of the MIC bias voltage from the audio codec (A7, B6), and leave the bias pin floating?
The EVAL board seems to be designed so that I can choose whether the microphone input is processed by the codec through a transfer or directly by the AP. If I connect it only to the codec (MIC CLK = Codec DMICCLK (C6), MIC DOUT = Codec DMICDAT1 (B9)), could any issues arise? (This is for STM32MP257FAI3). Or is there any additional software configuration required?
Let me know if you need further clarification or assistance!
