File content as of revision 2:e2441887b6d5:

/* mbed Microcontroller Library
 * Copyright (c) 2019 ARM Limited
 * SPDX-License-Identifier: Apache-2.0
 */

#include "mbed.h"
#include "platform/mbed_thread.h"

// Blinking rate in milliseconds
//#define BLINKING_RATE_MS                                                  5000

/*DigitalIn mybutton(USER_BUTTON);
DigitalOut myled(LED1);

int main()
{
    mybutton.mode(PullUp);

    while(1) {
        printf("Button state is: %d\n\r", mybutton.read());

        if (mybutton == 0) { // Button is pressed

            myled = !myled; // Toggle the LED state
            wait_ms(200); // 200 ms
        }
    }
}*/

/*PwmOut PWM1(LED1);

int main()
{
    PWM1.period(0.500); // set PWM period to 10 ms
    PWM1=0.5; // set duty cycle to 50%
}*/

/*Serial pc(USBTX, USBRX); // tx, rx
PwmOut led(LED1);
float brightness=0.0;

int main()
{
    pc.printf("Control of LED dimmer by host terminal\n\r");
    pc.printf("Press 'u' = brighter, 'd' = dimmer\n\r");
    while(1) {
        char c = pc.getc();
        wait(0.001);
        if((c == 'u') && (brightness < 0.1)) {
            brightness += 0.001;
            led = brightness;
        }

        if((c == 'd') && (brightness > 0.0)) {
            brightness -= 0.001;
            led = brightness;
        }
        pc.printf("%c %1.3f \n \r",c,brightness);
    }
}*/

/*AnalogIn my_adc(PA_7); //D11 on board
DigitalOut led(LED1);

int main()
{
    printf("\nSTM32 ADC example\n");

    while(1) {
        printf("ADC read = %f\n\r", (my_adc.read()*100));
        led = !led;
        wait_ms(1000);
    }
}*/

/*DigitalIn mybutton(D7);
DigitalOut myled(LED1);

int main() {

  mybutton.mode(PullNone);

  while(1) {

    printf("Button state is: %d\n\r", mybutton.read());

    if (mybutton == 0) { // Button is pressed

      myled = !myled; // Toggle the LED state
      wait(0.2); // 200 ms
    }
  }
}*/

DigitalOut led(LED1);
DigitalIn mybutton1(A4);
DigitalIn mybutton2(A5);
DigitalIn mybutton3(D2);
DigitalIn mybutton4(D7);
DigitalOut rele(D3);

int main()
{
    int a=0;
    mybutton1.mode(PullNone);
    mybutton2.mode(PullNone);
    mybutton3.mode(PullNone);
    mybutton4.mode(PullNone);
    
    while(1) {
        led = 1;
        rele = 0;
        if (mybutton1.read()==0){
            if (a==0){
                printf("Button1 state is: %d\n\r", mybutton1.read());
                a=a+1;
                wait(0.2);
            }
        }
        if (mybutton2.read()==0){
            if (a==1){
                printf("Button2 state is: %d\n\r", mybutton2.read());
                a++;
                wait(0.2);
            }
            else{
                a=0;
                wait(0.2);
            }
        }
        if (mybutton3.read()==0){
            if (a==2){
                printf("Button3 state is: %d\n\r", mybutton3.read());
                a++;
                wait(0.2);
            }
            else{
                a=0;
                wait(0.2);
            }
        }
        if (mybutton4.read()==0){
            if (a==3){
                printf("Button4 state is: %d\n\r", mybutton4.read());
                a++;
                wait(0.2);
            }
            else{
                a=0;
                wait(0.2);
            }
        }
        if (a==4) {
            rele=!rele;
            for (int i=0;i<10;i++){
                led = !led;
                wait(1);
            }
            rele=!rele;
            a=0;
        }
        printf("The code is entered on: %d\n\r", a);
        wait(0.2);
    }
}