STMicroelectronics AN2591 Microcontroller I/O Expander Application Note

About this manual

This document explains how to increase the number of input and output lines available on a microcontroller without selecting a more expensive part. It details methods to expand outputs using decoders (3-to-8 and 4-to-16) and shift registers (74HC595), allowing for independent control of multiple lines.

What's inside

• Expanding the number of outputs
• Using a decoder
• Using a shift register
• Expanding the number of inputs
• Using a multiplexer
• Using STMPE801 I2C bus expander
• Using the External Memory Interface

Specifications

Frequently asked questions

How can I expand the number of microcontroller outputs?

You can expand outputs using a decoder or a shift register to generate multiple output lines from fewer GPIOs.

Which IC is used to expand outputs to 8 lines using a decoder?

The M74HC138 3-to-8 line decoder is used to expand outputs to 8 lines.

Which IC is used to expand inputs to 16 lines?

The M74HC4067 16-to-1 multiplexer is used to expand input lines to 16.