File content as of revision 0:46dbd1b71de5:

#include "mbed.h"

DigitalOut myled(LED1);
DigitalOut Center(PA_9);
DigitalIn Port0(PA_8);
DigitalIn Port1(PA_10);

PortOut C(PortC,0xFF);
InterruptIn irqA(PA_1);
InterruptIn irq0(PA_8);
InterruptIn irq1(PA_10);

int z=0,Zustand=0,Zustandalt=0;

void isr(void)
{
   myled=!myled;

}

void isrEnc(void)
{
    Zustandalt=Zustand;
    if (Port0==0 && Port1==0) Zustand=0;
    if (Port0==1 && Port1==0) Zustand=1;
    if (Port0==1 && Port1==1) Zustand=2;
    if (Port0==0 && Port1==1) Zustand=3;
    if (Zustandalt==3 && Zustand==0) z++;
    if (Zustandalt==0 && Zustand == 3) z--;
    C=(z<<2)+Zustand;
}

int main() {
    Center=1;
 //   Port0.mode(PullDown);
 //   Port1.mode(PullDown);
    irqA.rise(&isr);
    irqA.mode(PullDown);
    irq0.rise(&isrEnc);
    irq0.fall(&isrEnc);
    irq0.mode(PullDown);
    irq1.rise(&isrEnc);
    irq1.fall(&isrEnc);
    irq1.mode(PullDown);
    
    RCC->AHBENR|=0b100;
    GPIOC->MODER=0x5555;
    //GPIOC->ODR=0x55;
    C=0;
    while(1) {

       /*
        myled = 1; // LED is ON
        wait(0.2); // 200 ms
        myled = 0; // LED is OFF
        wait(1.0); // 1 sec
        C=0;
        */
    }
}