STM32 SPI with ADXL372 - stm32

Question

I'm trying to read device id of ADXL372 with stm32 spi. But i'm always getting FF. If I change the address, still reads FF. I tried various configurations but I don't think it is the issue. I thought maybe my clock is so fast (170MHz) and i changed but it also didn't solve the problem. I don't understand what I'm doing wrong.
#include "main.h"
#include "SysClockConf.h"
char rxb;
uint8_t print=0;
uint16_t reading=0, value1=0, value2=0;
uint8_t bastir=0;
float deneme=0;
void Delay(uint32_t x)
{
while(x)
{
x--;
}
}
void transmit_string(char *s ){
//while( !( USART1->ISR & USART_ISR_TXE ) ) {};
while(*s){
USART1->TDR = *s ;
while( !( USART1->ISR & USART_ISR_TC ) );
s++;}
}
void transmit_char(char c){
//while( !( USART1->ISR & USART_ISR_TXE ) ) {};
USART1->TDR = c ;
while( !( USART1->ISR & USART_ISR_TC ) );
}
void transmit_number(uint8_t n){
//while( !( USART1->ISR & USART_ISR_TXE ) ) {};
USART1->TDR = n ;
while( !( USART1->ISR & USART_ISR_TC ) );
}
void spi_transmit_number(uint8_t n, uint8_t m){
GPIOA->BRR |= (GPIO_BRR_BR15);
while( !( SPI1->SR & SPI_SR_TXE ) ) {};
*(uint8_t*) & SPI1->DR = n ;
while( !( SPI1->SR & SPI_SR_TXE ) ) {};
*(uint8_t*) & SPI1->DR = m ;
GPIOA->BSRR |= (GPIO_BSRR_BS15);
}
uint8_t spi_read_number(uint8_t n){
GPIOA->BRR |= (GPIO_BRR_BR15);
while( !( SPI1->SR & SPI_SR_TXE ) ) {};
*(uint8_t*) & SPI1->DR = n ; //n = (adress shifted left one time + RW')
while( !( SPI1->SR & SPI_SR_RXNE ) ) {};
uint8_t result = SPI1->DR;
GPIOA->BSRR |= (GPIO_BSRR_BS15);
return result;
}
int k=0;
void Initialization(){
// Enable peripheral clocks: GPIOA, USART1, SPI1, ADC1 and TIMER4.
RCC->APB2ENR |= ( RCC_APB2ENR_USART1EN ) | ( RCC_APB2ENR_SPI1EN );
RCC->AHB2ENR |= ( RCC_AHB2ENR_GPIOAEN ) | ( RCC_AHB2ENR_GPIOBEN ) | ( RCC_AHB2ENR_ADC12EN );
RCC->APB1ENR1 |= RCC_APB1ENR1_TIM4EN;
// Configure pins PB3 (SPI1_CLK), PA15 (SPI1_CS), PB5 (SPI1_MOSI) and PB4 (SPI1_MISO) for SPI (AF5).
GPIOA->MODER |=(GPIO_MODER_MODE15_0);
GPIOA->MODER &= ~(GPIO_MODER_MODE15_1);
GPIOB->MODER &= ~(GPIO_MODER_MODE3_0);
GPIOB->MODER |= (GPIO_MODER_MODE3_1);
GPIOB->MODER &= ~(GPIO_MODER_MODE4_0);
GPIOB->MODER |= (GPIO_MODER_MODE4_1);
GPIOB->MODER &= ~(GPIO_MODER_MODE5_0);
GPIOB->MODER |= (GPIO_MODER_MODE5_1);
GPIOA->OSPEEDR |= (GPIO_OSPEEDER_OSPEEDR15) ;
GPIOB->OSPEEDR |= (GPIO_OSPEEDER_OSPEEDR3) | (GPIO_OSPEEDER_OSPEEDR4) | (GPIO_OSPEEDER_OSPEEDR4);
GPIOB->AFR[0] |= (0b0101<<GPIO_AFRL_AFSEL3_Pos) | (0b0101<<GPIO_AFRL_AFSEL4_Pos) | (0b0101<<GPIO_AFRL_AFSEL5_Pos);
// Configure pins A9 (TX), A10 (RX) for USART1 (AF7).
GPIOA->MODER &= ~(GPIO_MODER_MODE9_0);
GPIOA->MODER |= GPIO_MODER_MODE9_1;
GPIOA->MODER &= ~(GPIO_MODER_MODE10_0);
GPIOA->MODER |= (GPIO_MODER_MODE10_1);
GPIOA->OSPEEDR |= (GPIO_OSPEEDER_OSPEEDR9) | (GPIO_OSPEEDER_OSPEEDR10);
GPIOA->PUPDR = (GPIOA->PUPDR & ~(GPIO_PUPDR_PUPD9)) & ~(GPIO_PUPDR_PUPD10);
GPIOA->AFR[1] |= (0b0111<<GPIO_AFRH_AFSEL9_Pos) | (0b0111<<GPIO_AFRH_AFSEL10_Pos);
USART1->CR1 &= ~(USART_CR1_UE); //Disable UART1
//USART1->PRESC = 0b0001;
// Set the baud rate to 115200.
uint32_t SystemCoreClock = 170000000;
uint16_t uartdiv = SystemCoreClock / 115200;
USART1->BRR = uartdiv;
//Enable the USART peripheral.
USART1->CR1 |= ( USART_CR1_RE | USART_CR1_TE);
USART1->CR1 |= USART_CR1_RXNEIE;
USART1->CR1 |= USART_CR1_UE;
SPI1->CR1 &= ~(SPI_CR1_SPE); //Disable SPI1
SPI1->CR1 |= (0b111<<SPI_CR1_BR_Pos);; //Baud rate control fp/256
SPI1->CR1 |= (SPI_CR1_CPOL); //Clock polarity
SPI1->CR1 |= (SPI_CR1_CPHA); //Clock phase
SPI1->CR1 &= ~(SPI_CR1_RXONLY); //Disable receive only mode
SPI1->CR1 &= ~(SPI_CR1_BIDIMODE); //2-line unidirectional mode enabled
SPI1->CR1 &= ~(SPI_CR1_LSBFIRST); //MSB first mode enabled
SPI1->CR1 |= (SPI_CR1_SSM); //Software slave management enabled
SPI1->CR2 |= (SPI_CR2_SSOE); //MCU is set as master. The NSS pin is managed by the hardware.
SPI1->CR1 |= (SPI_CR1_MSTR); //Master configuration
SPI1->CR1 |= (SPI_CR1_SPE); //Enable SPI1
GPIOA->BSRR |= (GPIO_BSRR_BS15);
}
int main(void) {
HAL_Init();
SystemClock_Config();
Initialization();
spi_transmit_number(0x7E , 0x03); //0x3F => 126 (shift left and add 0 for write) power control adress //Full bandwidth measurement mode.
while ( 1 ) {
Delay(20000000);
reading=spi_read_number(0x01);
transmit_number(reading);
}
}