#define PB_ODR *(unsigned char*)0x5005
#define PB_IDR *(unsigned char*)0x5006
#define PB_DDR *(unsigned char*)0x5007
#define PB_CR1 *(unsigned char*)0x5008
#define PB_CR2 *(unsigned char*)0x5009

int main()
{
    int d;
    // Configure pins
    PB_DDR = 0x20;
    PB_CR1 = 0x20;
    // Loop
    do {
        PB_ODR ^= 0x20;
        for(d = 0; d < 15000; d++) { }
    } while(1);
}