MPU9150 example with TM4c123GXL

Hi

I have seen the example of MPU9150 with TM4C123GXL,and it works.

Now I want to use the information likes angular velocities.But when I add PWM signals and try to let motors run,it runs intermittent.

I found that there is a suspicious code as follow 

while(!g_vui8I2CDoneFlag)
{
ROM_SysCtlSleep();
}

So I command the code.The motors run normal.

But the values of angular velocities are zero.Only acceleration and magnetic are correct.

What's wrong?