Gravity: IO Expansion Shield for Arduino V7.1 Gravity: IO Expansion Shield for Arduino V7.1 is a shield board for Arduino that expands the capabilities of the I/O pins. Among other things, it has each pin with a power pair, the ability to include a 3.3 V voltage converter, a separate connector for I2C interfaces, SPI and a socket for XBee modules. Code DF027 Available Price €14.95