File content as of revision 0:3df753134818:

#include "mbed.h"
// https://developer.mbed.org/forum/electronics/topic/15346/
//------------------------------------
// Hyperterminal configuration
// 9600 bauds, 8-bit data, no parity
//------------------------------------
 
Serial pc(USBTX,USBRX);

Serial Serial1(PA_9,PA_10); 
Serial Serial3(PB_10,PB_11);  
Serial Serial4(PC_12,PD_2); 
Serial Serial5(PC_10,PC_11); 

int main() {
    Serial1.format(8, Serial::None, 1);
    Serial1.baud(9600);
 
    Serial3.format(8, Serial::None, 1);
    Serial3.baud(9600);
 
    Serial4.format(8, Serial::None, 1);
    Serial4.baud(9600);
 
    Serial5.format(8, Serial::None, 1);
    Serial5.baud(9600);
 
    pc.format(8, Serial::None, 1);
    pc.baud(9600);
    
    int i=0;
    while(1) { 
        Serial1.puts("AA");
        Serial3.puts("AA");
        Serial4.puts("AA");
        Serial5.puts("AA");
       
        pc.printf("This program runs since %d seconds.\r\n", i);
        i++;
        wait(1);
    }
}