Page 194 - ARM Based Microcontroller Projects Using MBED

180 8. INTERMEDIATE LEVEL PROJECTS

/*************************************************************************

REACTION TIMING
===============
This program measures the user reaction time. The User LED is lit randomly
and the program waits until the User button is pressed. The elapsed time
between the LED going ON and the button pressed is displayed on the PC
screen in milliseconds. This process is repeated after 3 seconds.
Author: Dogan Ibrahim
Date : August 2018
File : Reaction
**************************************************************************/
#include "mbed.h"
Serial MyPC(USBTX, USBRX);
Timer tim;
DigitalOut MyLED(LED1); // LED1 is output
DigitalIn button(BUTTON1); // BUTTON1 is input
int main()
{
int r;
float Duration;

MyPC.printf("\n\rReaction Timing"); // Display heading
MyPC.printf("\n\rPress the button as soon as you see the light...");

while(1)
{
tim.reset(); // Reset Timer to 0
r = rand() % 10 + 1; // Between 1 and 10
wait(r); // Random wait
tim.start(); // Start Timer
MyLED = 1; // LED ON
wait(0.05); // 50ms delay
MyLED = 0; // LED OFF
while(button == 1); // Wait for button
tim.stop(); // Stop Timer
Duration = tim.read_ms() - 50.0; // Read Duration
MyPC.printf("\n\rReaction Time (ms) = %f", Duration);
wait(3.0);
}
}
FIG. 8.41 Program listing.

FIG. 8.42 Typical output from the program.