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10.3 PROJECT 2—EXTERNAL INTERRUPT-DRIVEN EVENT COUNTER 287
10.3.3 Block Diagram
The block diagram of the project is shown in Fig. 10.5.
10.3.4 Circuit Diagram
Fig. 10.6 shows the circuit diagram of the project. A push-button switch is connected to
GPIO pin PA_0 of the development board such that the state of the button is normally at logic
HIGH and it goes to logic LOW when the button is pressed. The LCD is connected to PORTC
of the development board as in the previous project.
10.3.5 The PDL
The program PDL is shown in Fig. 10.7.
10.3.6 Program Listing
Mbed provides several functions for handling external interrupts. Table 10.2 presents a list
of the external interrupt functions. In this project we will be generating interrupts when GPIO
pin PA_0 edge falls from HIGH to LOW.
Fig. 10.8 shows the program listing (program: ExtInt). At the beginning of the program
mbed.h and the LCD header file TextLCD.h (see previous project. You can copy and paste
FIG. 10.5 Block diagram of the project.
FIG. 10.6 Circuit diagram of the project.
