We used the 4-digit 7-segment module to display a digital clock on a Raspberry Pi board via a shift register. Furthermore, we studied an OLED graphic display module, which can be accessed through an I2C port. The last topic is to use the OLED graphic display to develop a digital clock.

In the next chapter, we will learn how to build several applications with an LED dot matrix (8 x 8 LEDs). There are some project scenarios to illustrate how it works.