Help: MPU-6050 sensor data register all zero

Hi, guys:
we're start using MPU-6050 through I2C for accel and gyro.
These what I did.

1. I only configure 0x6b(power management reg) to be 0
2. I can read 0x75(Id register), which returns 0x68.
3. but all accel and gyro data register is zero

I noticed 6050 is default to be sleep mode, but I write 0 into 0x6b.

Did I miss anything to configure 6050? by default, it should be working.

Thanks

Dong