Introduction

Large electronic scoreboards and simple message signs are built from exactly this building block, a grid of individually controllable LEDs. In this experiment, an 8x8 LED dot-matrix display is driven through two 74HC595 shift register chips, using only three GPIO pins on the STM32F070RB, to display a simple alphanumeric character pattern.

2. Scope

This experiment covers understanding how a 74HC595 serial-in, parallel-out shift register expands a three-pin serial interface into eight parallel outputs, chaining two shift registers together to control both the row and column lines of an 8x8 matrix, implementing a bit-banged shift-out routine, and multiplexing the matrix row by row to display a static character pattern.

3. Prerequisite

3.1 Hardware

• STM32 Nucleo-F070RB development board

• 8x8 LED dot-matrix display module

• Two 74HC595 shift register integrated circuits, or a pre-wired driver breakout board combining both

• Breadboard and jumper wires

• Micro-USB cable

3.2 Software

• STM32CubeMX (standalone)

• STM32CubeIDE

• ST-LINK USB driver