Originally Posted by LKJ
Dennis are you sure i can plug the HT in both USB and my F9 on the same time, i get light in the red light diode on F9 with out turning F9 on, i am afraid to push 12V back in the USB and let the smoke out somewhere.
I just tested with a 12-20 volt supply at Vin to be completely sure. No problems at all. They will share the same 5-volt rail (usb and regulator), but you should not get any "high voltages" into your pc etc. Not perfect, but shouldn't cause problems. The LED you see turn on at your transmitter is caused by a low voltage (~1.6 volt) that can be seen at the other side of the regulator while powered with USB.
As always, it's on your own risk - but you should be fine
I have to defend my bachelor thesis in 9 hours, so I'll try to get some sleep.