#include "stm32f103xb.h"

int main() {

   // restart afio
   RCC->APB2RSTR |= RCC_APB2RSTR_AFIORST;
   // turn on b-pins
   RCC->APB2ENR |= RCC_APB2ENR_IOPBEN;
   // turn on afio
   RCC->APB2ENR |= RCC_APB2ENR_AFIOEN;
      // turn on I2C1
   RCC->APB1ENR |= RCC_APB1ENR_I2C1EN;
   // turn on pins 6, 7
   // AF and open-drain and 50MHz
   GPIOB->CRL |= 0xFF << 24;
   // set i2c1 freq
   I2C1->CR2 |= 2;
   // set ack
   I2C1->CR1 |= I2C_CR1_ACK;
   // set Pause
   I2C1->CCR |= 100;
   // trise
   I2C1->TRISE |= 9;
   // on i2c
   I2C1->CR1 |= I2C_CR1_PE;

   // start signal
   I2C1->CR1 |= I2C_CR1_START;
   while (!(I2C1->SR1 & I2C_SR1_SB));
   (void) I2C1->SR1;

   I2C1->DR |= 0x27 << 1;
   while (!(I2C1->SR1 & (I2C_SR1_ADDR)));
   (void) I2C1->SR1;
   (void) I2C1->SR2;

   I2C1->DR |= ('a' & 0xF0) | 0x08 | 0x04 | 0x01;
   while (!(I2C1->SR1 & (I2C_SR1_BTF)));
   (void) I2C1->SR1;
   (void) I2C1->SR2;

   I2C1->DR |= ('a' & 0xF0) | 0x08 | 0x00 | 0x01;
   while (!(I2C1->SR1 & (I2C_SR1_BTF)));
   (void) I2C1->SR1;
   (void) I2C1->SR2;

   I2C1->DR |= (('a' & 0x0F) << 4) | 0x08 | 0x04 | 0x01;
   while (!(I2C1->SR1 & (I2C_SR1_BTF)));
   (void) I2C1->SR1;
   (void) I2C1->SR2;

   I2C1->DR |= (('a' & 0x0F) << 4) | 0x08 | 0x00 | 0x01;
   while (!(I2C1->SR1 & (I2C_SR1_BTF)));
   (void) I2C1->SR1;
   (void) I2C1->SR2;

   I2C1->CR1 |= I2C_CR1_STOP;

   while (1);

   return 0;
}

bool EE_24C::WriteByte(uint16_t adr, uint8_t data)
{ 
  pI2C->CR1 = I2C_CR1_PE | I2C_CR1_START;
  while(!(pI2C->SR1 & I2C_SR1_SB));
  pI2C->DR = w_adr;
  while(!(pI2C->SR1 & I2C_SR1_ADDR))
  {
    if(pI2C->SR1 & I2C_SR1_AF)
    {
      pI2C->CR1 = I2C_CR1_PE | I2C_CR1_STOP;
      return false;
    }
  };
  pI2C->SR2;
  while(!(pI2C->SR1 & I2C_SR1_TXE));
  pI2C->DR = adr>>8;
  while(!(pI2C->SR1 & I2C_SR1_TXE));
  pI2C->DR = adr;
  while(!(pI2C->SR1 & I2C_SR1_TXE));
  pI2C->DR = data;   
  while(!((pI2C->SR1 & I2C_SR1_TXE) && (pI2C->SR1 & I2C_SR1_BTF)));   
  pI2C->CR1 = I2C_CR1_PE | I2C_CR1_STOP;
 
  return true;
}