TABLE OF CONTENTS A large number of embedded systems offer some form of display device to convey information to the user. The display can consist of anything from a light indicating that power is on, to a complex graphical display showing a representation of the process. Simple control systems can be equipped with complex displays while more complex systems can offer limited information to its user; there are no set rules as to how much information has to be displayed or how it has to be presented. The world of information display is becoming extremely complex, especially when you consider new technologies such as virtual reality.
In this chapter, I will take a very modest position and describe how to interface to LED (Light Emitting Diode) displays. Specifically, I provide you with a module that allows you to control up to 64 multiplexed LEDs. The LEDs can either be seven-segment digits or discrete devices. The module presented allows you to:
Display limited ASCII characters using seven-segment digits.
Display numbers.
Turn ON or OFF individual (discrete) LEDs.
The Light Emitting Diode, or LED, is a semiconductor device that produces visible light when a current flows through it as shown in the schematic of Figure 4.1. The intensity of the LED is proportional to the current flowing through the LED. LEDs that produce either RED, YELLOW, GREEN, or BLUE light are now commonly available. The most common color for LEDs is RED, while BLUE LEDs have just been...
