I am trying to get the serial terminal working with the TWR-K64F120M. I have the hello world demo program building and running on the target, but I can never see anything coming out on my PC. I have the JLink openSDA application running on the board and gdb is able to connect, load a program, and step through code no problem. I can see things initialize and the code gets to my PRINTF line. I can also see the activity LED on the board go crazy while printf is executing, so I believe everything on the board is actually running properly.
Now, on the linux side, when I plug into the USB debug port on the board I see a /dev/ttyACM0 device appear. I believe this is meant to be the virtual serial port connected to the K64. I am running the following to open a terminal to it: sudo screen /dev/ttyACM0 115200
Nothing ever shows up though. Am I going about this wrong? Maybe I have a jumper on the board set wrong? Any tips would be appreciated.