File content as of revision 5:18a4d0822e89:

#include "mbed.h"

BusIn rKeys(p16, p17, p18, p19, p20);
BusIn cKeys(p28, p27, p26, p25, p24, p23, p22, p21);

SPI spiLeft(p5, p6, p7); //SI, SO, SCK
SPI spiRight(p11, p12, p13);

char OpcodeLeft = 0x40;
char OpcodeRight = 0x50;

// mbed p15 is connected to ~chipSelect on the MCP23S17
MCP23S17 chipLeft = MCP23S17(spi, p15, OpcodeLeft);

// mbed p16 is connected to ~chipSelect on the MCP23S17
MCP23S17 chipRight = MCP23S17(spi, p16, OpcodeRight);

int main() {
    rKeys.mode(PullUp);
    cKeys.mode(PullUp);
    
    int rNeeded = 0x0F;
    //options: 0001 1110 (0x1E), 0001 1101 (0x1D), 0001 1011 (0x1B), 0001 0111 (0x17), 0000 1111 (0x0F)
    
    int cNeeded = 0xFE;
    //options: 1111 1110 (0xFE), 1111 1101 (0xFD), 1111 1011 (0xFB), 1111 0111 (0xF7),
    //         1110 1111 (0xEF), 1101 1111 (0xDF), 1011 1111 (0xBF), 0111 1111 (0x7F)
    
    //  Set all Port bits to output direction
    chipLeft.direction(PORT_A, 0x00);
    chipLeft.direction(PORT_B, 0x00);
    chipRight.direction(PORT_A, 0x00);
    chipRight.direction(PORT_B, 0x00);
    
    //chip.write(PORT_A, 0x00);
    
    while(1) {
        //check if it's the correct key
        if ((rKeys == rNeeded) & (cKeys == cNeeded)) {
            //get next note
            //rNeeded =
            //cNeeded =
            
            if (cNeeded == 0x00) { //end song with cNeeded = 0x00
                //modify uLCD to signify that we're done
                break;
            }
            
            //modify uLCD
            
            //turn on correct LED
            switch (rNeeded) {
                case 0x1D:
                chipLeft.write(PORT_A, ~cNeeded);
                break;
                case 0x1B:
                chipLeft.write(PORT_B, ~cNeeded);
                break;
                case 0x17:
                chipRight.write(PORT_A, ~cNeeded);
                break;
                case 0x0F:
                chipRight.write(PORT_B, ~cNeeded);
                break;
            }
        }
    }
}