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296 10. USING LIQUID CRYSTAL DISPLAYS (LCDs)
FIG. 10.15, CONT’D
No1: 20 <Enter>
No2: 10 <Enter>
Op: +
Res¼30
10.5.2 Aim
The aim of this project is to show how a keypad can be used with Mbed and the Nucleo-
F411RE development board in a project.
10.5.3 Block Diagram
Keypads are commonly used in microcontroller-based applications to enter numeric or al-
phanumeric data to the microcontroller. The most widely used type is a 4 4 keypad consis-
ting of 16 buttons, arranged in the form of four columns and four rows. The keypad used in
this project is the 4 4 keypad manufactured by mikroElektronika (www.mikroe.com)and
is shown in Fig. 10.16.
The block diagram of the project is shown in Fig. 10.17.
10.5.4 Circuit Diagram
The mikroElektronika 4 4 keypad is interfaced to a microcontroller using a 10-way IDC
(insulation-displacement contact) connector. Fig. 10.18 shows the connection diagram of the
keypad. The row signals are named as P4, P5, P5, and P7. Similarly, the column signals are
