I asked myself how they separate the usbinput and the 12v input why this works yesterday only when i plug the 12V too? Maybe the AFB26 is like a separator? And what happens when i change this to a 0 Ohm resistor? Has anyone replace this with 0 Ohm? Normaly the communication part has to work when only the usb is plugged in. But when only the 12V is plugged in the STM must be unpowerd.