FreeIMU for MPU9250 on Teensy 3.2

[iccentt]

I tried to calibrate MPU9250 on Teensy 3.2. Using the FreeIMU_serial.ino. When I compiled, there were lots of warning (It's ok, just ignore them). But there is on error:
Line 170: cmd1 = '0';
I checked and there was no declared for cmd1, so I thought that it would be a typo. Change back to cmd = '0'; and the code compiled and load to Teensy 3.2.
But when I tried to start cal_gui.py with MPU9250, the gui not response, nothing show up.
I also tried with IMU6050, some points came then the program also no response when I pressed stop sampling.
I don't know what happen here. Anyone can show me the light?
Thanks.