// Paste this at the top of your main file
#define EVER ;;

#define RCC_PERHIPHBASE   0x40021000
#define RCC_AHBENR        (RCC_PERHIPHBASE + 0x14)

#define GPIOB_PERIPHBASE  0x48000400
#define GPIOB_MODER       (GPIOB_PERIPHBASE + 0x00)
#define GPIO_ODR          (GPIOB_PERIPHBASE + 0x14)

// Paste this in your main() function
*((uint32_t *)RCC_AHBENR) |= 0b1000000000000000000; // Enable the GPIO Peripheral Clock (AHB Bus)
*((uint32_t *)GPIOB_MODER) |= 0b01; // Set the pin mode of port B pin 1 to GENERAL PURPOSE OUTPUT MODE

for (EVER) {
  *((uint32_t *)GPIO_ODR) ^= 0b1; // Toggle port B pin 1 by XOR-ing it

    // Pause for a bit by looping
  uint32_t i;
  for (i = 0; i < 100000; i++) {
    __asm("nop"); // This is the "correct" way to do nothing
  }
}