3. I2C and sensor connection
Seeeduino has prepared an extra row of I2C connections, which was reserved to reduce complexity when shipped out. You may solder it and get ready to use in minutes!
Vcc/GND/SCL/SDA for I2C, 3 and 2 are wired to Analog input pin 3/2.
Example of mounting an i2C interface 2-axis compass module, no extra wiring needed.