I have an custome hardware based on a Kinetis K70 uC. The USB device is connected to the D+ and D- signals of the USB interface using a mini USB connector (the traces go straight from the connector to the chip pins). The custom hardware is almost identical to the K70 tower hardware.
I can run most of the MQX example programs on this board but run into a problem regarding the USB CDC-ACM example. When I plug the USB cable into the board, the JTAG interface unit LEDs go dark and my debugger in uVision crashes.
I double checked the connections, the lines are connected correctly. What I noticed is that the USB 5V input is not connected to VREGIN, instead it is connected to an GPIO for detecting a change.
Since connecting the USB seems so simple, what could be wrong? Dop I need to change the configuration since VREGIN is not conncted? Any advice is appreciated.