File content as of revision 2:26e1d1bf3d08:

#include "mbed.h"

//DigitalOut led1(LED1);
DigitalOut led1(P0_13);// nRF52840 io
DigitalOut led2(P0_14);
DigitalOut led3(P0_15);
DigitalOut led4(P0_16);

InterruptIn button1(P0_11);//(USER_BUTTON nRf52840);
InterruptIn button2(P0_12);
InterruptIn button3(P0_24);
InterruptIn button4(P0_25);
int button3_flag=0;

void button1_pressed()
{
    led1 = 0;
}

void button1_released()
{
    led1 = led2 =led3 =led4 = 1;// LED OFF
    //led1 = 0;
}

void button2_pressed()
{
    led2 = 0;

}

void button2_released()
{
    led1 = led2 =led3 =led4 = 1;
    //led1 = 0;
}

void button3_pressed()
{
    button3_flag = 1;

}

void button3_released()
{
    led1 = led2 =led3 =led4 = 1;
    //led1 = 0;
    button3_flag=0;
}

void button4_pressed()
{
    led4 = 0;

}

void button4_released()
{
    led1 = led2 =led3 =led4 = 1;
    //led1 = 0;
}


int main()
{
    led1 = led2 =led3 =led4 = 0;

    button1.fall(&button1_pressed);
    button1.rise(&button1_released);

    button2.fall(&button2_pressed);
    button2.rise(&button2_released);

    button3.fall(&button3_pressed);
    button3.rise(&button3_released);

    button4.fall(&button4_pressed);
    button4.rise(&button4_released);


    while (true) {
        if(button3_flag == 1) {
            led3 = 0;
            wait(0.1);
            led3 = 1;
            wait(0.1);
        } else {


            led1 = !led1;
            wait(0.5);
            led2 = !led2;
            wait(0.5);
            led3 = !led3;
            wait(0.5);
            led4 = !led4;
            wait(0.5);
        }
    }
}