File content as of revision 0:75151492e147:

/*Program Example 7.9: Sets the mbed up for async communication, and exchanges data with a similar node, sending its own switch positions, and displaying those of the other. 
                                                                 */
#include "mbed.h"
Serial async_port(p9, p10);          //set up TX and RX on pins 9 and 10
DigitalOut red_led(p25);             //red led
DigitalOut green_led(p26);           //green led
DigitalOut strobe(p7);               //a strobe to trigger the scope
DigitalIn switch_ip1(p5);
DigitalIn switch_ip2(p6);
char switch_word ;                   //the word we will send
char recd_val;                       //the received value 
  
int main() {
  async_port.baud(9600);             //set baud rate to 9600 (ie default)
  //accept default format, of 8 bits, no parity
  while (1){
    //Set up the word to be sent, by testing switch inputs
    switch_word=0xa0;                 //set up a recognisable output pattern
    if (switch_ip1==1)
      switch_word=switch_word|0x01;   //OR in lsb
    if (switch_ip2==1)
      switch_word=switch_word|0x02;   //OR in next lsb
    strobe =1;                        //short strobe pulse 
    wait_us(10);
    strobe=0;
    async_port.putc(switch_word);     //transmit switch_word
    if (async_port.readable()==1)     //is there a character to be read?
      recd_val=async_port.getc();     //if yes, then read it

    //set leds according to incoming word from slave
    red_led=0;              //preset both to 0
    green_led=0; 
    recd_val=recd_val&0x03; //AND out unwanted bits
    if (recd_val==1)
      red_led=1;
    if (recd_val==2)
      green_led=1;
    if (recd_val==3){
      red_led=1;
      green_led=1;
    }

  }
}