stm32f401ccAudioNative

stm32 black pill usb sound card last one:

https://www.youtube.com/watch?v=0MmWp3HdV2A

https://www.youtube.com/watch?v=GbiTxVYopDI

https://www.youtube.com/watch?v=TnEBuS5ONsY

High quality, low noise DAC based on 2 PWM timer channels with virtual software Sigma Delta ADC between stream from usb and PWM output. There is implemented "sigma-delta floating point encoder" workaround of native stm32f401 limit 10.5 bits on 44100 Hz (1904 levels=84MHz/44.1KHz ) So, we can have for only $3 ,very low noise , high sound quality solution, which better then most onboard sound cards !

There is implemented virtual software second order sigma delta adc for the shift quantization noise to high frequency. see here (it [provide useful links too at the end of document):

https://www.analog.com/media/en/training-seminars/tutorials/MT-022.pdf

But instead one bit ( two levels ) i use more bits (0-MAX_LEVELS) Same technology can be used for esp32 high quality sound rendering.

14.04.2022 :

Added second order sigma-delta

number of LCD from zero to 2

minor bugs fixed

optional external i2s module

21.04.2022 : -- Change to open drain timer1 PWM outputs( PA8 PA9 ) config for better noise supression.

27.04.2022

-- pll bug fix

-- up pwm freq to 384KHz - significant sound quality improvment

-- add tty output

7.06.2022

-- Merge with cdu6 (spdif,pll,int,lcds)

-- add binary(2 lcd & i2s by default) & makefile into Release -- add ref stm s*1357