How to waste time making tinyUSB work on GD32F303
How to spend 2 days on silly things while porting tinyUSB to GD32F303/lnArduino : Be absolutely sure to put the GD32F303 on a bluepill PCB with a bad R10 (i.e. 10k instead of 1.5k) Be absolutely sure to have a dodgy usb connector on that bluepill board (of course it's even better if you bought a full box of replacement usb connectors of all sizes). Use a bad usb cable The only thing that was an actual real problem is you have to pull down PA12/D+ for ~ 10 ms so that the device is re-detected after reset (thanks Google, RogerClark, victor_pv,...) Oh well, it kinda works now.