Hi,
For grove-ultrasonic sensor, please plug into gpio12, NOT I2C. then follow below instructions.
pi@raspberrypi:~ $ git clone https://github.com/Seeed-Studio/grove.py.git
pi@raspberrypi:~ $ cd grove.py/
pi@raspberrypi:~/grove.py $ sudo python setup.py install
pi@raspberrypi:~/grove.py $ cd grove
pi@raspberrypi:~/grove.py/grove $ python grove_ultrasonic_ranger.py 12
Detecting distance…
223.759947152 cm
142.985376818 cm
223.776389813 cm
5.44663133292 cm
9.18733662572 cm
16.5700912476 cm
Warning: the distance from the ultrasonic ranger is not accurate
26.7234341852 cm
223.31188465 cm
223.792832473 cm
11.107017254 cm
Bill