The default settings for communication with the PMIC is I²C. Changing to SPI requires a minor change to the jumper settings and those settings changes in the case of multiple EVMs in a stackup configuration. These jumper settings are highlighted in red in Figure 3-6. The first jumper to place is on the SPI_EN option on connector J20. Placing this jumper connects the micro controller to the SPI bus, which is connected to all available PMICs through the EVM stack connection through J29. In a multiple EVM stackup, this jumper can only be placed on the controller EVM with the USB connection to the host computer. The SPI does not have a device ID and, therefore, the chip select is used to determine which PMIC receives and responds to commands on the SPI bus. The signals SCL2/CS and GPIO2 on J25 can only be jumpered on the controller EVM, which connects to the USB. Stacked target EVMs must have the CS selected with the S3 dip switch on the bottom of the board. For example, with first target board GPIO2 switch and SPI_CS1 switches can be closed, other switches open. And, on second target board GPIO2 and SPI_CS2 switches must be closed and so on. See Table 3-7 for details on S3 switch settings.

Figure 2-6 Interface Settings for SPI Communication