2 MCU GPIO Expansion

Similarly, MCU expansion can be used in generic GPIO pins on the MCU, where the ADC is not necessary to utilize. Here, there may be a need to monitor digital triggers or digital signals or send a plethora of digital cues. This may take a toll on the total GPIO count while requiring fairly limited processing. Multiplexing across these digital I/Os, as shown in Figure 2-1, can reduce the number of GPIOs required to do this.

Figure 2-1 Expansion of 1 MCU GPIO to Four Digital I/Os Using A Multiplexer.

It is important to note that TI multiplexers are passive FET switches that simply allow any signal through as long as they meet the recommended operation conditions listed in the datasheet. While many of multiplexers and switches from TI are defined as analog multiplexers and signal switches, this does not limit their ability to pass through digital signals. That is to say, digital signals can pass through these analog multiplexers as well, as long as they meet the recommended operation conditions for the switch in use. The important considerations to take into account when picking a multiplexer when implementing GPIO expansion is the On-Capacitance, Leakage Current and Signal Voltage Range. For more information see the Multiplexer Specifications section.