#include "stm32f4xx.h"
#include <math.h>
#include <stdio.h>

#define CS 0

int main()
{
  //init SPI
  RCC_TypeDef * rcc = RCC;

  //enable GPIO clocks
  SET_BIT(rcc->AHB1ENR, RCC_AHB1ENR_GPIOAEN);
  SET_BIT(rcc->AHB1ENR, RCC_AHB1ENR_GPIOFEN);
  SET_BIT(rcc->APB2ENR, RCC_APB2ENR_USART1EN);

  //CS - PF0 (output), SCK - PF1 (output), SIO - PF2 (input)
  GPIO_TypeDef * gpiof = GPIOF;
  SET_BIT(gpiof->MODER, 1 << 0 | 1 << 2);
  CLEAR_BIT(gpiof->MODER, 1 << 1 | 1 << 3 | 1 << 4 | 1 << 5);

  //configure GPIOA pins to alternate mode
  GPIO_TypeDef * gpioa = GPIOA;
  SET_BIT(gpioa->MODER, 1 << 21 | 1 << 19);
  CLEAR_BIT(gpioa->MODER, 1 << 20 | 1 << 18);

  //choose correct alternate function
  SET_BIT(gpioa->AFR[1], 7 << 8 | 7 << 4);


  //CS to 1, so no transmission
  SET_BIT(gpiof->ODR, 1 << 0);

  USART_TypeDef * usart1 = USART1;


  //na TC77 od lewej: CS, Vss(GND), SCK, SI/O, Vdd(Vcc)


  int read_bit = 0;
  float result = 0;

  while (1)
  {
    //set CS to 0 to start transmission
    CLEAR_BIT(gpiof->ODR, 1 << CS);
    int buffer = 0;

    for (int i = 12; i >= 0; i--)
    {
      CLEAR_BIT(gpiof->ODR, 1 << 1);
      for (int i = 0; i < 1000; i++);
      SET_BIT(gpiof->ODR, 1 << 1);
      for (int i = 0; i < 1000; i++);


      read_bit = READ_BIT(gpiof->IDR, 1 << 2);
      //shift right to get bit value - 0 or 1
      read_bit = read_bit >> 2;
      buffer |= (read_bit << i);
    }

    //stop transmission
    SET_BIT(gpiof->ODR, 1 << 0);

    //buffer negative or not - U2 + conversion
    //TC77 documentation LSB is 0,0625 celcius degree
    result = 0;
    for (int i = 0; i < 12; i++)
    {
            if (buffer & (1 << i))
            {
                    result += 0.0625 * pow(2, i);
            }
    }
    if (buffer & (1 << 12))
    {
            result -= 0.0625 * pow(2, 12);
    }

    char text[50];
    sprintf(text, "Temperature: %f \n", result);

    //configure USART1

    //USART enable
    SET_BIT(usart1->CR1, 1 << 13);

    //8 bit word length
    CLEAR_BIT(usart1->CR1, 1 << 12);

    //set baud rate to 104.1875 mantissa 104 fractional 3
    SET_BIT(usart1->BRR, 104 << 3 | 3 << 0);

    //set TE bit in CR1 to send idle frame
    SET_BIT(usart1->CR1, 1 << 3);

    for (int i = 0; i < 50; i++)
    {

      if(text[i]!='\0')
        usart1->DR = text[i];
    }




  }


  return 0;
}