File content as of revision 0:b1af0438774e:

#include "mbed.h"

I2C i2c(p28, p27);

DigitalOut MotorL(P1_15);         
DigitalOut MotorLf(P1_1);   
DigitalOut MotorLr(P1_0);   
 
DigitalOut MotorR(P0_21);
DigitalOut MotorRf(P1_3);
DigitalOut MotorRr(P1_4);

DigitalOut Blau(P1_28);

int taster = 0;

int main() {
    
    Blau = 0;
    MotorL = MotorR = 1;
    MotorLf = 1;
    MotorRf = 1;
    
    i2c.start();
       i2c.write(0x40);   // Adresse des PCA9555 = 40 
                          // das letzte Bit = 0 -> schreiben  0040 0000
       i2c.write(0x06);   // Befehl für das IO Port 0 -> siehe SCHEMA des PCA9555
       i2c.write(0x00);   // Schalte alle Pins des Ports als OUTPUT
    i2c.stop();  
    
    i2c.start();
                i2c.write(0x40);  // Adresse & schreiben
                i2c.write(0x02);  // 
                i2c.write(~5);  // schriebn auf Port 0 den INVERSEN Wert von btn
            i2c.stop();
    
    while(1)
    {
        i2c.start();
                i2c.write(0x40);
                i2c.write(0x01);        
       
            i2c.start();
                i2c.write(0x41); 
                taster = i2c.read(0);
            i2c.stop();
            
        if(taster == 1 || taster == 3 || taster == 5 || taster == 7 || taster == 9 || taster == 11 || taster == 13 || taster == 15)
        {
            MotorLf = MotorRf = 0;
            MotorLr = MotorRr = 1;
            i2c.start();
                i2c.write(0x40);  // Adresse & schreiben
                i2c.write(0x02);  // 
                i2c.write(~80);  // schriebn auf Port 0 den INVERSEN Wert von btn
            i2c.stop();
        }
        else if(taster == 2 || taster == 3 || taster == 6 || taster == 7 || taster == 10 || taster == 11 || taster == 14 || taster == 15)
        {
            i2c.start();
                i2c.write(0x40);  // Adresse & schreiben
                i2c.write(0x02);  // 
                i2c.write(~5);  // schriebn auf Port 0 den INVERSEN Wert von btn
            i2c.stop();
            MotorLf = MotorRf = 1;
            MotorLr = MotorRr = 0;
        }
        else if(taster == 255)
        {
            MotorLf = MotorRf = 1;
            MotorLr = MotorRr = 0;
        }
    }
}