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
