pls answer some question

[Aether-yang]

1. What is the difference between this git and the following git project?
   https://github.com/sdima1357/stm32f401ccAudioNative
2. can i connect dircetly to the earphone (resistance about 32R)? PA8 to left earphone and PA9 to right earphone? can it play normly?
   
3. Can I use stm32 adc to sample audio (3.5mm lined mic, resistance about 2.2K). any suggestion to the circuit？

[sdima1357]

1 stm32f401cdu6 and stm32f401ccu6 are not same chips
2 Сan i connect directly to the earphone? - You can't . You hear nothing. Currently output cascade configured in open drain mode.If you put stm32 output in push-pull mode, Stm32 can give only about 20 milliamper and You hear more noise.
3 You can, but you have to add some amplifier to map input signal to 0-3.3v. And you have only 12 bit signal. I suggest You use microphones with i2s output. Google for "Microphone I2S"