File content as of revision 0:c912ef4f5206:

/*Sets the mbed up as Master, and exchanges data with a slave, sending its own switch positions, and displaying those of the slave.*/
#include "mbed.h"
SPI ser_port(PTD2, PTD3, PTD1); //mosi, miso, sclk
DigitalOut red_led(LED1); //red led
DigitalOut green_led(LED2); //green led
DigitalOut cs(PTC16); //this acts as “slave select”
DigitalIn switch_ip1(SW2);
DigitalIn switch_ip2(SW3);
char switch_word ; //word we will send
char recd_val; //value return from slave

int main() {
   while (1){
//Default settings for SPI Master chosen, no need for further configuration
//Set up the word to be sent, by testing switch inputs
   switch_word=0xa0; //set up a recognizable output pattern
     if (switch_ip1==0)
     switch_word=switch_word|0x01; //OR in lsb, check if the botton is pressed
     if (switch_ip2==0)
     switch_word=switch_word|0x02; //OR in next lsb, check if the botton is pressed
     cs = 0; //select slave ("active low")
     recd_val=ser_port.write(switch_word); //send switch_word and receive data. set a initial value for recd_val (dummy)
     cs = 1;
     wait(0.01);//wait for slave to response
//set leds according to incoming word from slave
     red_led=1; //preset both to off
     green_led=1;
     recd_val=recd_val&0x03; //AND out unwanted bits
     if (recd_val==1)
     {red_led=0; //red on, green off
      green_led=1;}
     if (recd_val==2)
     {red_led=1; //red off, green on
      green_led=0;}
     if (recd_val==3){
      red_led=0; //both on
      green_led=0;
   }
 }
}