The I²C bus for this design was broken into two separate communication channels. One of these channels uses the UCB0 peripheral to communicate with an upstream host. This allows for data and control registers to be maintained in the MSP430 that can be read from or written to by the system host. This peripheral also allows for a hardware I²C address to be assigned in the firmware, providing a system that can be configured to communicate directly with a host that is using existing hardware and firmware.

The other I²C channel using UCB1 acts as a downstream facing port to control the charging system for this design. The PCA9546A I²C MUX is used to interface directly with multiple downstream devices using the same address. This uses all four channels of the PCA9546A to communicate with two BQ25731 devices at address 0x6B, and two gauges at address 0x16, as is outlined by the Smart Battery Data Specification 1.1.