RCC->AHBENR |= RCC_AHBENR_GPIOAEN;
   
    GPIOA->MODER |= GPIO_MODER_MODER4_0;            //port in output mode
    GPIOA->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR4;       //high speed
    GPIOA->OTYPER &= ~(GPIO_OTYPER_OT_4);           //push-pull
    GPIOA->BSRR = GPIO_BSRR_BS_4;                   //set one to self
   
    GPIOA->MODER |= GPIO_MODER_MODER5_1;            //alternate
    GPIOA->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR5;       //high speed
    GPIOA->OTYPER &= ~(GPIO_OTYPER_OT_5);           //push-pull
   
    GPIOA->MODER &= ~(GPIO_MODER_MODER6);           //input mode
    GPIOA->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR6;       //high speed   
    GPIOA->PUPDR |= GPIO_PUPDR_PUPDR6_0;            //pull-up
    //GPIOA->BSRR = GPIO_BSRR_BS_6;
   
    GPIOA->MODER |= GPIO_MODER_MODER7_1;            //alternate
    GPIOA->OSPEEDR |= GPIO_OSPEEDER_OSPEEDR7;       //high speed
    GPIOA->OTYPER &= ~(GPIO_OTYPER_OT_7);           //push-pull
   
    RCC->APB2ENR |= RCC_APB2ENR_SPI1EN;
   
    SPI1->CR1 |= SPI_CR1_MSTR;
    SPI1->CR1 |= SPI_CR1_SSI;
    SPI1->CR1 |= SPI_CR1_SSM;
    SPI1->CR1 |= SPI_CR1_BR;

    SPI1->CR2 = SPI_CR2_DS;
   
    SPI1->CR1 |= SPI_CR1_SPE; 

if ((SPI1->SR & SPI_SR_TXE) == SPI_SR_TXE) /* Test Tx empty */
    //{
        SPI1->DR = 0xFF;
        GPIOB->BSRR = GPIO_BSRR_BS_1;
   // }