Conquering the STM32F4 on the discovery board step-by-step. Commit history is tutorialesque, but not clean of course.
 
 
 
 
 
heck 2c84fb60e7 MX: set clock to 168MHz / enable USB as device only as serial port, send "hello heck". works. 2 years ago
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usbd_cdc.c MX: set clock to 168MHz / enable USB as device only as serial port, send "hello heck". works. 2 years ago