SPI communication on STM8 controller doesn't work

Question

I'm trying to send data through spi with the Stm8 controller. The problem is that I can't see anything happening on the oscilloscope (even the SPI clock doesn't show) on the pins 6 and 5 with this code:

#include "stm8l15x_spi.h"
#include "imagedata.h"
#include "delay.h"
#include "stm8l15x.h"

void initSPIMaster(void);

This is how I try to call the functions in the main:

void main(void)
{ CLK_PeripheralClockConfig(CLK_Peripheral_SPI1, ENABLE);
  initSPIMaster();  
  SPI_BiDirectionalLineConfig(SPI1, SPI_Direction_Tx); //Selects the data transfer direction 

  SPI_SendData(SPI1, 0xCD); }

Here is how I configured the pins on the board and the SPI_SendData function:

void initSPIMaster()
{
    
GPIO_Init( GPIOB ,GPIO_Pin_7, GPIO_Mode_In_PU_No_IT ); //Miso input
GPIO_Init( GPIOB, GPIO_Pin_6, GPIO_Mode_Out_PP_Low_Fast); //MOSI
GPIO_Init( GPIOB, GPIO_Pin_5, GPIO_Mode_Out_PP_Low_Fast); //CLK
GPIO_Init( GPIOB, GPIO_Pin_4, GPIO_Mode_Out_PP_Low_Fast); //CS

GPIOB->DDR = (1<<GPIO_Pin_6)| (0<<GPIO_Pin_7);  //MOSI output, MISO input
GPIOB->DDR |= (1<<GPIO_Pin_5); //SCK output
GPIOB->CR1  = (1<<GPIO_Pin_6)| (1<<GPIO_Pin_5); //MOSI push-pull & SCK
//GPIOB->CR1    = (1<<GPIO_Pin_5); 

GPIOB->DDR |= (1<<GPIO_Pin_4); //set CS as output
GPIOB->CR1 |= (1<<GPIO_Pin_4); //set CS as push-pull*/
  
}



void SPI_SendData(SPI_TypeDef* SPIx, uint8_t Data) //declared in the stm8l15x_spi.h
{
  SPIx->DR = Data; /* Write in the DR register the data to be sent*/
}

I checked if the pins are wrongly configured but this should be right according to the datasheet of this board. Maybe I missed something in this code. Unfortunetaly there isn't much information about this topic on the internet but hopefully I can find a solution here. Does anyone know how to do this?