I just got a NUCLEO-F401RE, I plugged it into my Mac with a mini USB cable, and I see LD1 (red) blinking slowly, LD3 (red) solid, and LD2 (green) blinking rapidly. It doesn’t show up as a mass storage device in Finder. I tried plugging it into a Windows machine and same result, it’s not showing up in My Computer.
If I hold down the RESET button, LD2 turns off, but LD1 and 3 are unchanged.
Something’s not right - what do the blinking LEDs mean?