File content as of revision 0:fa5e89cbad4d:

/*Program Example 7.6: I2C Slave, when called transfers switch state to mbed acting as Master, and displays state of Master's switches on its leds.
                                                                              */

#include <mbed.h>
I2CSlave slave(p9, p10);          //Configure I2C slave
DigitalOut red_led(p25);          //red led
DigitalOut green_led(p26);        //green led
DigitalIn  switch_ip1(p5);
DigitalIn  switch_ip2(p6);
char switch_word ;                //word we will send
char recd_val;                    //value received from master

int main()
{
    slave.address(0x52);
    while (1) {
        //set up switch_word from switches that are pressed
        switch_word=0xa0; //set up a recognisable output pattern
        if (switch_ip1==1)
            switch_word=switch_word|0x01;
        if (switch_ip2==1)
            switch_word=switch_word|0x02;
        slave.write(switch_word); //load up word to send
        //test for I2C, and act accordingly
        int i = slave.receive();
        if (i == 3) {           //slave is addressed, Master will write
            recd_val= slave.read();
        }
        //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;
        }
    }
}