In Figure 9-4, the ultra low-power microcontroller, MSP430G2132, controls the I²C data traffic of configuration data and conversion results for the analog inputs and outputs. In Figure 9-5, the TMS320F28035 controls both the I²C interface, for communication to a DAC for analog outputs, and a SPI interface, for communication to an ADC for analog inputs.

Low-power data converters build the analog interface to sensors and actuators. The ISO164x device provides the required isolation between different ground potentials of the system controller, remote sensor, and actuator circuitry to prevent ground loop currents that otherwise may falsify the acquired data.

The entire circuit operates from a single 3.3-V supply. A low-power push-pull converter, SN6501, drives a center-tapped transformer with an output that is rectified and linearly regulated to provide a stable 5-V supply for the data converters.

Figure 9-4 Isolated I²C Data Acquisition System

Figure 9-5 Isolated I²C and SPI Data Acquisition System