Expanding I/O Pins of Microcontroller by Cascading Shift Registers

In modern embedded systems, the demand for increased digital input/output (I/O) capabilities often exceeds the native pin count of micro controllers. One of the common solutions is the usage of shift registers to expand the I/O capabilities. It is common to use 2–4 shift register chips for expanding the GPIO pins, and references are available; in this paper, we provide a reference for technical support for using shift registers in large numbers. We present a practical approach to expanding I/O pins while handling a large number of shift registers in both directions by using Parallel In Serial Out (PISO) and Serial In Parallel Out (SIPO) shift registers, the SN74HC595 and SN74HC165, respectively. This paper dwells on the implementation by including circuit design, software integration, and challenges faced while cascading many shift registers and providing solutions.