Oh,thanks to your help.and to be honest, i just want to enable two i2c slave devices(BMP180 & MPU9150).and i found that each one can work well if i only touch one sensor to the I2C6.
but if i connect two sensors to I2C6, it can't work.and i use i2cdetect -y -r 6, there is no sensor founded.
so,i'm sorry for that do you have any advice??