#include "link.h"
#include "stm32f411.h"

const char msg[] = "blink ";

static void
delay (void)
{
  volatile unsigned int i;
  for (i = 0; i < 500000; i++);
}

static void
reset_handler (void)
{
  unsigned int *src, *dst;
  unsigned int off;

  /* relocate .data to sram  */
  src = &_data_lma_start;
  dst = &_data_vma_start;

  while (dst < &_data_vma_end)
    *(dst++) = *(src++);

  /* initialize .bss  */
  dst = &_bss_vma_start;

  while (dst < &_bss_vma_end)
    *(dst++) = 0;

  /* (todo) usart pin setup (alt func and enable port clock)  */

  /* UE: USART enable  */
  *USART_CR1 |= (1u << 13); /* 1: USART enable  */
  /* M: Word length  */
  *USART_CR1 &= ~(1u << 12); /* 0: 1 Start bit, 8 Data bits, n Stop bit  */
  /* STOP: STOP bits  */
  *USART_CR2 &= ~(3u << 12); /* 00: 1 Stop bit  */
  /* the clock frequnecy is 16mhz initially, so for a baud rate of 115.2 KBps we
   * need to set USARTDIV=8.6875  */
  *USART_BRR = (8u << 4) | 11; /* mantissa and fraction (/16)  */
  /* TE: Transmitter enable  */
  *USART_CR1 |= (1u << 3); /* 1: Transmitter is enabled  */

  /* blink blink setup  */
  *RCC_AHB1ENR |= (1u << 2);
  *GPIOC_MODER &= ~(3u << 26);
  *GPIOC_MODER |= (1u << 26);

  while (1)
    {
      /* speak  */
      off = 0;
      do
        {
          /* TXE: Transmit data register empty  */
          if (!(*USART_SR & (1u << 7)))
            continue;

          *USART_DR = msg[off++];
        }
      while (off < sizeof msg);

      /* blink  */
      *GPIOC_ODR ^= (1u << 13);
      delay ();
    }
}

__attribute__ ((section (".vector_table"), used))
static unsigned long const vector_table[] = {
  (unsigned long) &_sram_end,
  (unsigned long) reset_handler,
};