i installed correctly the SunControl and i can execute the script testSunControl.py. Same if i do "i2cdetect -y 1" i see 04.
Later on, i install the GrovePi+ (...) and when i do "i2detect -y 1" i still see 04 and the 40 for the GrovePi. I connect the Usb grove to a digital port on the GrovePi and I2c to an i2c port on the GrovePi. I still able to run the script testSunControl.py. I can request sensors connected on the GrovePi and receive correct answers.
The problem appear when i m using i2cdump -y 1 0x40 or i2cdump -y 1 0x04 its show "X" for all answers and i lose contact with the two boards because if i do again "i2cdetect -y 1", no i2c device is found.