int main(void)
{
/*!< At this stage the microcontroller clock setting is already configured,
this is done through SystemInit() function which is called from startup
file (startup_stm32f4xx.s) before to branch to application main.
To reconfigure the default setting of SystemInit() function, refer to
system_stm32f4xx.c file
*/
uint8_t d0 = 0xd9; // 11011001, test data0




// declare SPI init data structure
SPI_InitTypeDef spi2;

// declare GPIO init data structure
GPIO_InitTypeDef gpiob;

// enable SPI2 clock
RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI2, ENABLE);

// enable SPI2 pins
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);

// connecting Alternate Functions to GPIOB pins
GPIO_PinAFConfig(GPIOB, GPIO_PinSource13, GPIO_AF_SPI2);
GPIO_PinAFConfig(GPIOB, GPIO_PinSource15, GPIO_AF_SPI2);


// GPIOB configuration
gpiob.GPIO_Pin = GPIO_Pin_13 | GPIO_Pin_15;
gpiob.GPIO_Mode = GPIO_Mode_AF;
gpiob.GPIO_OType = GPIO_OType_PP;
gpiob.GPIO_Speed = GPIO_Speed_50MHz;
gpiob.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOB, &gpiob);

// initializing the SPI2
SPI_I2S_DeInit(SPI2);
spi2.SPI_Direction = SPI_Direction_1Line_Tx;
spi2.SPI_DataSize = SPI_DataSize_8b;
spi2.SPI_CPOL = SPI_CPOL_High;
spi2.SPI_CPHA = SPI_CPHA_1Edge;
spi2.SPI_FirstBit = SPI_FirstBit_LSB;
spi2.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_8;
spi2.SPI_Mode = SPI_Mode_Master;

SPI_Init(SPI2, &spi2);


// enable the SPI2
SPI_Cmd(SPI2, ENABLE);

// sending the data
while (SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_TXE) == RESET);
SPI_I2S_SendData(SPI2, (uint8_t)d0);



while (1)
{}
}

int main(void)
{
/*!< At this stage the microcontroller clock setting is already configured,
this is done through SystemInit() function which is called from startup
file (startup_stm32f4xx.s) before to branch to application main.
To reconfigure the default setting of SystemInit() function, refer to
system_stm32f4xx.c file
*/
uint8_t d0 = 0xd9; // 11011001, test data0



// declare SPI init data structure
SPI_InitTypeDef spi2;

// declare GPIO init data structure
GPIO_InitTypeDef gpiob;

// enable SPI2 clock
RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI2, ENABLE);

// enable SPI2 pins
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);




// GPIOB configuration
gpiob.GPIO_Pin = GPIO_Pin_13 | GPIO_Pin_15 | GPIO_Pin_12;
gpiob.GPIO_Mode = GPIO_Mode_AF;
gpiob.GPIO_OType = GPIO_OType_PP;
gpiob.GPIO_Speed = GPIO_Speed_50MHz;
gpiob.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOB, &gpiob);


// connecting Alternate Functions to GPIOB pins
GPIO_PinAFConfig(GPIOB, GPIO_PinSource13, GPIO_AF_SPI2);
GPIO_PinAFConfig(GPIOB, GPIO_PinSource15, GPIO_AF_SPI2);
GPIO_PinAFConfig(GPIOB, GPIO_PinSource12, GPIO_AF_SPI2);



// initializing the SPI2
SPI_I2S_DeInit(SPI2);
spi2.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
spi2.SPI_DataSize = SPI_DataSize_8b;
spi2.SPI_CPOL = SPI_CPOL_High;
spi2.SPI_CPHA = SPI_CPHA_1Edge;
spi2.SPI_FirstBit = SPI_FirstBit_LSB;
spi2.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_8;
spi2.SPI_Mode = SPI_Mode_Master;
spi2.SPI_NSS = SPI_NSS_Hard;
SPI_Init(SPI2, &spi2);
SPI_SSOutputCmd(SPI2, ENABLE);

// enable the SPI2
SPI_Cmd(SPI2, ENABLE);

// sending the data
while (SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_TXE) == RESET)
{
}
SPI_I2S_SendData(SPI2, (uint8_t)d0);

// make sure the transmit buffer is free
// while (SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_TXE) == RESET);
// SPI_I2S_SendData(SPI2, d0);
// we are not reading data so be sure that the character goes to the shift register
//while (SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_TXE) == RESET);
// and then be sure it has been sent over the wire
// while (SPI_I2S_GetFlagStatus(SPI2, SPI_I2S_FLAG_BSY) == SET);


while (1)
{}
}

//-----------------------------------------------------------------------------
//    void init_SPI2(void)
//-----------------------------------------------------------------------------
void init_SPI2(void)
{
    SPI2->CR1 =
            SPI_CR1_SSM
        | SPI_CR1_SSI
        | SPI_CR1_MSTR
        | SPI_CR1_BR_2 | SPI_CR1_BR_1 | SPI_CR1_BR_0;

    SPI2->CR2 =
            SPI_CR2_SSOE;

    SPI2->CR1 =
            SPI_CR1_SPE
        | SPI_CR1_SSM
        | SPI_CR1_SSI
        | SPI_CR1_MSTR
        | SPI_CR1_BR_2 | SPI_CR1_BR_1 | SPI_CR1_BR_0;
}

//-----------------------------------------------------------------------------
//    void __inline init_SYSTEM(void)
//-----------------------------------------------------------------------------
void __inline init_SYSTEM(void)
{
    RCC->AHB1ENR = RCC_AHB1ENR_GPIOBEN;
    RCC->APB1ENR = RCC_APB1ENR_SPI2EN;
}

//-----------------------------------------------------------------------------
//    void __inline init_GPIO(void)
//-----------------------------------------------------------------------------
void __inline init_GPIO(void)
{
    GPIOB->MODER = GPIO_MODER_MODER13_1  | GPIO_MODER_MODER14_1  | GPIO_MODER_MODER15_1
    GPIOB->AFR[1] = (5 << ((13 - 8) << 2)) | (5 << ((14 - 8) << 2)) | (5 << ((15 - 8) << 2));
}

int main(void)
{
/*!< At this stage the microcontroller clock setting is already configured,
this is done through SystemInit() function which is called from startup
file (startup_stm32f4xx.s) before to branch to application main.
To reconfigure the default setting of SystemInit() function, refer to
system_stm32f4xx.c file
*/
uint8_t d0 = 0xd9; // 11011001, test data0



// enable SPI2 clock
((RCC_TypeDef *) (RCC_BASE))->APB1ENR |= RCC_APB1ENR_SPI2EN;

// enable GPIOB clock
((RCC_TypeDef *)(RCC_BASE))->AHB1ENR |= RCC_AHB1ENR_GPIOBEN;


// GPIOB configuration
((GPIO_TypeDef *)(GPIOB_BASE))->MODER |= (GPIO_MODER_MODER13_1 |
GPIO_MODER_MODER15_1 );
((GPIO_TypeDef *)(GPIOB_BASE))->OTYPER |= 0x00;
((GPIO_TypeDef *)(GPIOB_BASE))->OSPEEDR |= (GPIO_OSPEEDER_OSPEEDR13_1 |
GPIO_OSPEEDER_OSPEEDR15_1 );
((GPIO_TypeDef *)(GPIOB_BASE))->PUPDR |= 0x00;
//((GPIO_TypeDef *)(GPIOB_BASE))->IDR |= RCC_AHB1ENR_GPIOBEN;
//((GPIO_TypeDef *)(GPIOB_BASE))->ODR |= RCC_AHB1ENR_GPIOBEN;
//((GPIO_TypeDef *)(GPIOB_BASE))->BSRRL |= RCC_AHB1ENR_GPIOBEN;
//((GPIO_TypeDef *)(GPIOB_BASE))->BSRRH |= RCC_AHB1ENR_GPIOBEN;
//((GPIO_TypeDef *)(GPIOB_BASE))->LCKR |= RCC_AHB1ENR_GPIOBEN;
((GPIO_TypeDef *)(GPIOB_BASE))->AFR[1] |= (0x500000 | 0x50000000);

// configure SPI2
((SPI_TypeDef *) (SPI2_BASE)) -> CR1 |= (SPI_CR1_SPE | SPI_CR1_CPOL |
SPI_CR1_CPHA | SPI_CR1_MSTR |
SPI_CR1_BR_1 | SPI_CR1_SSM | SPI_CR1_SSI);



// transmit the test data
while ( ( (((SPI_TypeDef *) (SPI2_BASE)) -> SR) & 0x2 ) == RESET)
{
// wait until TXE bit is 1
}
((SPI_TypeDef*)(SPI2_BASE)) -> DR = d0;

while (1)
{}
}