"Hardware Chiptune Project" for STM32F4Discovery Evaluation Board Ported from Atmega88 to STM32F4DISCOVERY Board http://www.linusakesson.net/hardware/chiptune.php STM32 Reference Manual http://www.st.com/content/ccc/resource/technical/document/reference_manual/20/f5/7a/01/0a/e1/47/ef/DM00180366.pdf/files/DM00180366.pdf/jcr:content/translations/en.DM00180366.pdf CS43L22 Cirrus Logic Audio DAC https://www.cirrus.com/cn/pubs/proDatasheet/CS43L22_F2.pdf Video https://www.youtube.com/watch?v=iltSLcUl9Xk