#define PMC_BASE 0x7000e400
#define APB_MISC_BASE 0x70000000

void _start() {
  *(volatile unsigned int *)(PMC_BASE + 0x1b4) = 0x0; // Clear PWR_DET_LATCH
  *(volatile unsigned int *)(PMC_BASE + 0x1b8) =
      0xFFFFFFFF; // Force High Voltage Mode

  *(volatile unsigned int *)(APB_MISC_BASE + 0x8BC) =
      0x00000000; // UART1_TX Pad Control

  *(volatile unsigned int *)(PMC_BASE + 0x50) = 0x50575221; // "PWR!"

  volatile unsigned int *uart = (unsigned int *)0x70006000;
  while (1) {
    *uart = 0x55; // 01010101 pattern
    for (volatile int i = 0; i < 1000; i++)
      ;
  }
}