File content as of revision 0:73793c67337f:

 /* Sets the mbed up as Slave, and exchanges data with a Master,
sending its own switch positions, and displaying those of the Master. as SPI slave
 */
#include "mbed.h"
SPISlave ser_port(p11, p12, p13, p14); //mosi, miso, sclk, ssel
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 return from slave

 int main() 
 {
//default formatting applied
    while(1) {
        //set up switch_word from switches that are pressed
        switch_word=0xa0; //set up a recognizable output pattern
        if (switch_ip1==1)
            switch_word=switch_word | 0x01; 
        if (switch_ip2==1)
            switch_word=switch_word | 0x02;
        if(ser_port.receive()) { //test if data transfer has occurred
            recd_val = ser_port.read(); // Read byte from master
            ser_port.reply(switch_word); // Make this the next reply
                            }
        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;
                    }
    }
}