Page 193 - ARM Based Microcontroller Projects Using MBED

8.15 PROJECT 12—EVENT COUNTER 179
BEGIN
Configure LED1 as output and BUTTON1 as input
Display heading
DO FOREVER
Reset Timer
Generate a random number 1 to 10 into r
Wait randomly r seconds
Start the Timer
Flash the LED for 50ms
Wait until button is pressed
Stop the Timer
Calculate the elapsed time
Display the elapsed time
Wait 3 seconds
ENDDO
END
FIG. 8.40 Program PDL.

An infinite loop is formed using a while statement. Inside this loop, a random number is
generated between 1 and 10 and this is used as an argument in the wait statement. Therefore,
the program waits randomly between 1 and 10s. The LED is then flashed for 50ms and the
program starts the Timer and waits until the button is pressed. When the button is pressed,
the Timer is stopped and the elapsed time is read in milliseconds and stored in variable Du-
ration. In all, 50ms is subtracted from the elapsed time since the duration between the ON
and OFF times is 50ms. The Duration is then displayed on the PC screen. The program re-
peats after 3s of delay.
Fig. 8.42 shows a typical output from the program.

8.15 PROJECT 12—EVENT COUNTER

8.15.1 Description

This is an event counter project. The User button is used to simulate the occurrence of ex-
ternal events such that every time the button is pressed a count is incremented by one and the
total count is displayed on the PC screen continuously.

8.15.2 Aim
The aim of this project is to show how the various serial communication functions can
be used.
8.15.3 The PDL

Fig. 8.43 shows the program PDL.