File content as of revision 2:92715b8bee8f:

#include "mbed.h"
#include "PCF8574.h"

#define BAUD 9600
InterruptIn event(p12);
Serial pc(USBTX, USBRX); 
PCF8574 io(p9,p10,0x40);
int data1 , data2;

void display(int data)
{
switch (data)
{
    case 238: pc.printf("SW1 \n\r"); break;
    case 237: pc.printf("SW2 \n\r"); break;
    case 235: pc.printf("SW3 \n\r"); break;
    case 231: pc.printf("SW4 \n\r"); break;
    case 222: pc.printf("SW5 \n\r"); break;
    case 221: pc.printf("SW6 \n\r"); break;
    case 219: pc.printf("SW7 \n\r"); break;
    case 215: pc.printf("SW8 \n\r"); break;
    case 190: pc.printf("SW9 \n\r"); break;
    case 189: pc.printf("SW10 \n\r"); break;
    case 187: pc.printf("SW11 \n\r"); break;
    case 183: pc.printf("SW12 \n\r"); break;
    case 126: pc.printf("SW13 \n\r"); break;
    case 125: pc.printf("SW14 \n\r"); break;
    case 123: pc.printf("SW15 \n\r"); break;
    case 119: pc.printf("SW16 \n\r"); break;
    }    
}

        void trigger() 
            {
                //event.fall(NULL);
               //printf("triggered!\n");
                io.write(0x0f);
                data1 = io.read();
            
                io.write(0xf0);
                data2 = io.read();
                
                display(data1+data2);
                //wait(0.2);
                //event.fall(&trigger);
            }

int main()
{    
    pc.printf("Start\n\r");
    event.fall(&trigger);
    //event.rise(&trigger);
    while(1) 
    {
    
    }
}