I just ran into a quick problem with my STM32F103C8T6 that I got to play with. Whenever I tried to upload code, I kept getting this error:
Error in initializing ST-Link device. Reason: No device found on target.
I know that I had my settings correct (using an ST-Link, SWD, and outputting to Intel hex format) and that the device was still alive since it was running other code; however, even when trying with a different programmer and reverifying the pins, nothing happened.
To fix this, I simply held down the reset button and as I hit upload, I let the button go.
This seems to have fixed the problem, but it is very strange. Anyway, I hope that someone else can benefit from this..