File content as of revision 108:5621bbcc10f5:

/*
    Project: 21_TW_Ex_9_1_v5
    File: main.cpp
    
    An example similar to T&W example 9.1. Green junction will flash 
    continuously. Blue junction will toggle in response to depressing the user 
    button.
    
    Created by Dr. C. S. Tritt
    Last revised: 10/17/21 (v. 1.0)
*/
#include "mbed.h"

InterruptIn myButton(USER_BUTTON); // Button is normally high. Goes low w/press.

DigitalOut bluLED(D4); // Blue and green LED junctions.
DigitalOut grnLED(D3);

void myISR() { // Simple ISR toggles the blue LED junction when called.
    bluLED = !bluLED; // Toggle blue junction.
}

int main() {
    const int GRN_PERIOD = 500;
    bluLED = 0; // Turn blue & green off at start.
    grnLED = 0; 
    
    myButton.fall(&myISR); // "Register" the ISR routine. Sets vector.
    
    while(true) {
        grnLED = !grnLED; // Toggle green junction.
        ThisThread::sleep_for(GRN_PERIOD); // Sleep for GRN_PERIOD mS.
    }
}