Page 167 - ARM Based Microcontroller Projects Using MBED

8.6 PROJECT 4—FOUR-DIGIT 7-SEGMENT LED EVENT COUNTER 153
8.6.2 Aim
The aim of this project is to show how an event counter can be designed and the events
displayed on a four-digit multiplexed 7-segment LED display. It is assumed that pressing
the User button creates an external event.

8.6.3 Block Diagram
The block diagram of the project is as in Fig. 8.16.

8.6.4 Circuit Diagram

The circuit diagram of the project is as in Fig. 8.8. In addition, the onboard User button is
used to create external events.

8.6.5 The PDL
The PDL of the program is very similar to the PDL given in Fig. 8.14, but here the count is
incremented when the User button is pressed.

8.6.6 Program Listing

Fig. 8.17 shows the program listing (program: EventCounter). The program listing is very
similar to the one given in Fig. 8.15. In this program, the User button is configured as digital
input. In this program, the count (CNT) is incremented by one inside the main program every
time the button is pressed. The delay has been removed from the main program. The ISR
(function Refresh) refreshes the display at every 5ms.

8.6.7 Suggestions for Additional Work

Modify the program given in Fig. 8.17 so that the count starts from 1000 and counts done by
one every time the button is pressed.

FIG. 8.16 Block diagram of the project.