从机地址应该由从机决定，由从机的硬件连接决定，可以看下手册，:  The slave address of the MPU-60X0 is b110100X which is 7 bits long. The LSB bit of the 7 bit address is determined by the logic level on pin AD0. This allows two MPU-60X0s to be connected to the same I2C bus.
When used in this configuration, the address of the one of the devices should be b1101000 (pin AD0 is logic
low) and the address of the other should be b1101001 (pin AD0 is logic high).
你软件上写0x68  0x69是没有作用的，只能由从机自己决定。