1.1. Battery Gauge on the I2C Bus
A battery gauge is a device which continuously monitors the state of a battery's capacity and displays it to the user in a simple form. Often in embedded systems, the status of the battery supply is monitored remotely. Communication between the embedded system and battery gauge can be facilitated through an industry standard two-wire I2C bus and an interfacing device. Because of its low overhead, the two-wire communication link minimizes the number of traces required on the PCB to monitor the power source.
A supported Altera device can easily serve as the interfacing device. The I2C interface allows the supported Altera device to access readings from the battery gauge remotely. An I2C serial interface consists of a data line (SDA) and a clock line (SCL). Both the lines are bidirectional and are pulled up to the VCC of the system. This bus is also a common bus for any other I2C-compliant device in the system.