STM32F0 Basic Part1

//STM32F0 Reference manual PG 127/742
Turn on/off a Pin (Example Pin C8)

  /* Enable clock for GPIOC                                                   */
  RCC->AHBENR |= (1 << 19);

  GPIOC->MODER  |= (1 << 16);//Set pin C8 as output

  GPIOC->OTYPER &= ~(1 << 8);//Set pin 8 output as internal push-pull

  GPIOC->BSRR |= (1 << 24);//Turn Pin C8 off
  GPIOC->BSRR |= (1 << 8);//Turn  C8 on



Read a pin (Example Pin A0)
RCC->AHBENR  |= (1 << 17);               /* Enable GPIOA clock         */

GPIOA->PUPDR    |=  (1 << 0);         /* PA.0 is  Pull up         */


if((GPIOA->IDR & (1 << 0))==(1 << 0))//read pin state
{
       //High
 }
 else
 {
        //Low
  }

Set up external pin interrupt (Example Pin A0)
 Config pin as input (above)
    EXTI->IMR |= (1 << 0); //unmask External interrupt line 0 (PA0)

    EXTI->RTSR |= (1 << 0); //Enable rising edge trigger of line 0
    EXTI->FTSR    |= (1 << 0); //Enable falling edge trigger of line 0
   
    NVIC_EnableIRQ(EXTI0_1_IRQn);//Enabe EXTI0_1 IRQ


put this segment in the source file
//use extern "C" if the file is .cpp

extern "C" {
    void EXTI0_1_IRQHandler(void)
    {
         //to do
    }
}

I2C Write, Read sequence

Write
Start, Write_Address, Data_Bytes, Stop

Read
Start, Write_Address, Register_Address, Read_Address, Stop