File content as of revision 0:4ec99b800425:

/*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 recognizable 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
        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;
        }
    }
}