Stm32f401cdu6 Audio Save

#stm32f401cdu6_Audio

stm32 green pill usb sound card last one (press on image for video):

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

30.04.2022

-- cheeper!!! green pill (stm32f401cdu6)version. Can buy here ( US $2.63 ) https://www.aliexpress.com/item/4001062944589.html

02.05.2022

-- detected problems with new STM32Cube_FW_F4_V1.27.0 audio driver. please build with <=STM32Cube_FW_F4_V1.26.0 . WIP

26.06.2022

-- add spdif output via i2s data pin