STM32F407 SPI reciveing only 0xFF (255) or 0 - c

Question

Recently I have been trying to receive a data from my STM32F407 motion sensor. I have the following code:
uint8_t SPI1_Read(){
GPIO_ResetBits(GPIOA, GPIO_Pin_4); // CS low
while(SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_TXE)==RESET){}
SPI_I2S_SendData(SPI1, 0x00);
while(SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE)==RESET){}
return SPI_I2S_ReceiveData(SPI1);
}
void SPI1_Write(uint8_t data){
while(SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_TXE)==RESET){}
SPI_I2S_SendData(SPI1, data);
while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET){}
SPI_I2S_ReceiveData(SPI1);
}
volatile static int vrednost, vrednost1, vrednost2;
int main(void)
{
// Vkljuci driver za GPIOD
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);
// Nastavi registre za LED diode
GPIO_InitTypeDef inicializacijskaStruktura;
inicializacijskaStruktura.GPIO_Mode = GPIO_Mode_OUT;
inicializacijskaStruktura.GPIO_OType = GPIO_OType_PP;
inicializacijskaStruktura.GPIO_PuPd = GPIO_PuPd_NOPULL;
inicializacijskaStruktura.GPIO_Speed = GPIO_Speed_100MHz;
inicializacijskaStruktura.GPIO_Pin = GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
GPIO_Init(GPIOD, &inicializacijskaStruktura);
SPI_and_GPIO_Init();
// init
SPI1_Write(0x20);
SPI1_Write(0x47);
SPI1_Write(0x0F);
SPI1_Write(0xBC);
while(1)
{
SPI1_Write(0x20);
vrednost=SPI1_Read();
SPI1_Write(0x24);
vrednost1=SPI1_Read();
SPI1_Write(0x28);
vrednost2=SPI1_Read();
if(vrednost<122){
GPIO_SetBits(GPIOD, GPIO_Pin_12);
}
else{
GPIO_ResetBits(GPIOD, GPIO_Pin_12);
}
if(vrednost1<122)
GPIO_SetBits(GPIOD, GPIO_Pin_13);
else
GPIO_ResetBits(GPIOD, GPIO_Pin_13);
if(vrednost2<122)
GPIO_SetBits(GPIOD, GPIO_Pin_14);
else
GPIO_ResetBits(GPIOD, GPIO_Pin_14);
}
}
void SPI_and_GPIO_Init(){
GPIO_InitTypeDef GPIO_InitStructure;
/* Enable the SPI periph */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);
/* Enable SCK, MOSI and MISO GPIO clocks */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA , ENABLE);
/* Enable CS GPIO clock */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE, ENABLE);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource5, GPIO_AF_SPI1);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource6, GPIO_AF_SPI1);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource7, GPIO_AF_SPI1);
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_DOWN;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
/* SPI pins configuration */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5|GPIO_Pin_6|GPIO_Pin_7;
GPIO_Init(GPIOA, &GPIO_InitStructure);
/* SPI configuration -------------------------------------------------------*/
SPI_I2S_DeInit(SPI1);
SPI_InitTypeDef SPI_InitStructure;
SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;
SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low;
SPI_InitStructure.SPI_CPHA = SPI_CPHA_1Edge;
SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;
SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_4;
SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
SPI_InitStructure.SPI_CRCPolynomial = 7;
SPI_InitStructure.SPI_Mode = SPI_Mode_Master;
/* Enable SPI1 */
SPI_SSOutputCmd(SPI1, ENABLE);
SPI_Cmd(SPI1, ENABLE);
/* Configure GPIO PIN for Lis Chip select */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOE, &GPIO_InitStructure);
/* Deselect : Chip Select high */
GPIO_SetBits(GPIOE, GPIO_Pin_3);
}
Upper code works fine, but the problem is that always when I try to read motion sensor, i get 0xFF or in another words 255. I read data by sending dummy text and then read data.
I have been also given an advice to set Slave Select pin (SS) to zero, but I don't know how to do that.
Does anybody know?

Answer 1

To hazard a guess - typically with SPI, SS is driven low (enable) at the start of each write/read then driven high (disable) at the end of each write/read to indicate end of transmission. Without pulling out the board, that's what I'd bet on.
If that's not it - ST is pretty good at providing examples. The source code on their product page includes an example using their MEMs accelerometer (Utilities/STM32F4-Discovery/stm32f4_discovery_lis302dl.c/.h).