It need 3 steps to use I2cTool. See Pic1.
Note: Before using I2cTool, you should connect the phone and PC using usb cable, and you are sure having the root privileg of the phone.
1st step: Click the "Connect" button to let I2cTool to connect the phone.
2nd step: Open the camera app in the phone to entry preview mode.
3rd step: Enter the right i2c address, register address and value of the sensor, then click "Read" or "Write" to complete the operation. The "mutiple control" is same.