Using a VEX Controller
By Daniel Ramirez
The Great VEX LCD
Display Experiment
An LCD display is a very useful device that is widely used in consumer electronics,
commercial, industrial, and automotive applications to display menus, status
information, and diagnostic details. LCDs first became widely available when
they were used to display alphanumeric information in calculators, alarm clocks,
and watches.
There are two types of LCD displays: the newer graphics displays and the classic
character LCD displays in either monochrome or color. The new OLED bright color
LCDs are also gaining popularity. Learning how to use these versatile output
devices is a must for anyone involved in electronics.
This article will show you how to connect a low cost character LCD to a VEX
microcontroller. There are two methods of interfacing LCDs: one is to use a parallel
bus and the other is to use a serial interface such as RS-232, SPI, or I2C. In this
experiment, the LCD is connected via a parallel bus which is used to send data to
the display. This is the easiest method to use and understand.
An LCD display for a VEX microcontroller is also useful for debugging and testing embedded applications used in robotics since it allows you to display data in debug output statements using the
printf function. An LCD display also provides a convenient
method of displaying text and status and error messages to
the VEX user via a portable User Interface (UI). When this is
combined with a keypad, it provides visual feedback from
the embedded VEX microcontroller that is not connected to
a PC (or laptop) when running in autonomous mode. This
makes it a very portable diagnostic tool, especially during
contests or in the school lab environment. In one evening,
you can be displaying data from your VEX controller with
your own homemade LCD application.
60 SERVO 06.2010
Character LCD displays such as those shown in
Figure 1 are widely available in 16, 24, and 40 character
formats with one to five lines. They can easily be found on
the Internet or at surplus electronics stores for relatively low
prices. In order to display more characters per line, higher
resolution displays (such as the large blue one shown in
Figure 1) are needed that can easily show up to 80
characters. Some styles can also draw geometric figures
such as lines, boxes, circles, and triangles in monochrome,
and newer LCDs can draw text and graphics in color. These
kinds of displays are often found in vending machines, bank
terminals, commercial, and consumer electronics devices,
and other embedded controller applications. Some of these
LCDs have a simple serial RS-232 interface that can be
