Designing Embedded Hardware

Adding a Small Display with I²C

You can use I2C to add simple LCDs (and other equivalent display technologies) to your embedded computer. These LCDs are usually just a few lines of text high but are useful for simple message display functions. Matrix Orbital (http://www.matrix orbital.com) produces a number of display modules that are easy to interface, such as the VFD2041. This display module is 80 characters wide by four lines deep. The interface circuit is shown in Figure 9-29, and as you can see, there’s almost nothing to it. The types of LCDs found in laptops are considerably more complicated, and interfacing them to small processors is just not an option. But for simple message displays (such as on the front panel of an appliance), a circuit like this is ideal.

Figure 9-29. Interfacing a VFD2041 display using I²C

Many Matrix Orbital displays also come with RS-232C interfaces, so if your embedded processor doesn’t support I²C, it’s still easy to add a small display.

In the next chapter, well see how to add a serial port to an embedded computer and connect it to both external host computers and peripherals. We’ll also look at several forms of serial interface, including RS-232C, IrDA and USB.