If you use an Arduino Uno R2 or an older Arduino, which lack separate I²C pins, the SDA and SCL pins on the Zumo Shield will not be connected to anything. To use an I²C device on those pins, you can connect SDA to A4 and SCL to A5 yourself by bridging across those two sets of pins in the front expansion area. [[Pololu-Zumo-Shield-Arduino-seneur-inertiel|Section 3.c]] further explains the I²C lines and the jumpers connecting them to the on-board compass module. | If you use an Arduino Uno R2 or an older Arduino, which lack separate I²C pins, the SDA and SCL pins on the Zumo Shield will not be connected to anything. To use an I²C device on those pins, you can connect SDA to A4 and SCL to A5 yourself by bridging across those two sets of pins in the front expansion area. [[Pololu-Zumo-Shield-Arduino-seneur-inertiel|Section 3.c]] further explains the I²C lines and the jumpers connecting them to the on-board compass module. |