#define GPIO_BASE 0x6000d000

void _start() {
  *(volatile unsigned int *)(0x60006010) |= (1 << 8);

  *(volatile unsigned int *)(GPIO_BASE + 0x500 + 0x10) = 0x01; // CNF: GPIO
  *(volatile unsigned int *)(GPIO_BASE + 0x500 + 0x14) = 0x01; // OE: Output

  while (1) {
    *(volatile unsigned int *)(GPIO_BASE + 0x500 + 0x18) = 0x01; // HIGH
    for (volatile int i = 0; i < 5000; i++)
      ;
    *(volatile unsigned int *)(GPIO_BASE + 0x500 + 0x18) = 0x00; // LOW
    for (volatile int i = 0; i < 5000; i++)
      ;
  }
}