Important note about the i2c pins at J7:
In the manual, SDA and SCL has been switched. According to the manual, pin 5 is SCL and pin 6 is SDA. This is wrong.
The correct pinout is
1 +5V
2 +5V
3 +5V
4 GPIO9
5 I2C3_SDA
6 I2C3_SCL
7 GND
