VEX DIY LCD Display and Keypad
VEX CONTROLLER
ANALOG / DIGITAL
FIGURE 2. In order
to connect the keypad and
LCD to the microcontroller
for this UI application, just
follow the wiring diagram
shown here.
Keen on Keypads
Connecting a 4 x 4 Keypad
A keypad allows the user to enter data and commands
to an embedded controller or the data entry for the user
interface as shown in Figure 1. The keypad may also be
used to enter text and numeric data like in a calculator
application. The keypad and LCD combination makes an
excellent portable data input device so robot behavior can
be changed on the fly. The keypad is connected to the
controller using an eight-bit bus — similar to the four-bit bus
used on the LCD display.
50 SERVO 08.2010
Connecting the keypad is very simple. The only parts
required are the keypad, some pin headers, and wire-wrap
wire as shown in the figure. Connections to other kinds of
microcontrollers usually require four 10K to 470K pull-ups
and eight 100 ohm resistors in series (or having weak pull-ups enabled on their input pins if this feature is available).
The VEX controller has these components already
connected to it internally. Again, our keypad is connected to
the controller via an eight-bit parallel bus, so that only eight
additional I/O pins are required (for the keypad) in addition
