Stm32f103RB no envía datos en modo Full duplex SLAVE SPI

Estoy trabajando en la placa del núcleo stm32f103rb y quiero enviar datos y recibir datos utilizando stm32f103 en modo esclavo. Puedo obtener datos del maestro pero no puedo enviar datos al maestro. No sé qué causó el problema (¿inicializar o interrumpir o marcar?) ¿Cómo hago un arreglo?

#include "stm32f10x.h"                  /*Device header*/
#define rxBufferSize 4
#define txBufferSize 5
#define SPI_SLAVE_PIN_NSS 12
#define SPI_SLAVE_PIN_SCK 5
#define SPI_SLAVE_PIN_MISO 6
#define SPI_SLAVE_PIN_MOSI 7



uint8_t txSize=5;
 uint8_t SPI_SLAVE_Buffer_Rx[rxBufferSize],RxIdx=0,TxIdx=0;
 uint8_t SPIz_Buffer_Tx[txBufferSize] = {'s','e','l','a','m'};

/*****************************************************************************/
/*                           FUNCTIONS                                       */
/*****************************************************************************/

/**
 * @brief  Initializes the SPI
 * @param  None
 * @retval None
 */
void RCC_Configuration(void);
void GPIO_Configuration(void);
void NVIC_Configuration(void);


int main(void)
{

    RCC_Configuration();

    NVIC_Configuration();

    GPIO_Configuration(); 

    SPI_InitTypeDef SPI_InitStructure;

   /* SPI_SLAVE configuration -------------------------------------------------*/
    SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
    SPI_InitStructure.SPI_Mode = SPI_Mode_Slave;
    SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;

    SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low;                                                                         /* NOTE: Clock polarity low */

    SPI_InitStructure.SPI_CPHA = SPI_CPHA_1Edge;                                                                       /* NOTE: Clock phase 2 edges */

    SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;                                                                          /* NOTE: Chip select is controlled by software */

    SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_64;

    SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;                                                                 /* NOTE: MSB First */

    SPI_InitStructure.SPI_CRCPolynomial = 7;                                                                           /* NOTE: Default CRC calculation polynomial value */


    SPI_Init(SPI1, &SPI_InitStructure);

    SPI_I2S_ITConfig(SPI1, SPI_I2S_IT_RXNE, ENABLE);

 //       SPI_I2S_ITConfig(SPI1, SPI_I2S_IT_TXE, ENABLE);

/* Enable SPI_SLAVE */
 /* SPI_I2S_ClearITPendingBit(SPI1, SPI_I2S_IT_RXNE);
  SPI_I2S_ClearITPendingBit(SPI1, SPI_I2S_IT_TXE);*/

    SPI_Cmd(SPI1, ENABLE);

    while(1) {


}

}
void RCC_Configuration(void)
{  
   // RCC_PCLK2Config(RCC_HCLK_Div2); 

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA |RCC_APB2Periph_SPI1, ENABLE);

}

void GPIO_Configuration(void)
{
 GPIO_InitTypeDef GPIO_InitStructure;


  /* Configure SCK and MOSI pins as Input Floating */

      GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
      GPIO_InitStructure.GPIO_Pin =SPI_SLAVE_PIN_SCK | SPI_SLAVE_PIN_MOSI  ; 
      GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
      GPIO_Init(GPIOA, &GPIO_InitStructure);


      GPIO_InitStructure.GPIO_Pin =  SPI_SLAVE_PIN_MISO     
      GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
      GPIO_Init(GPIOA, &GPIO_InitStructure);





}
void NVIC_Configuration(void)
{
NVIC_InitTypeDef NVIC_InitStructure;

        NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1); 
    NVIC_InitStructure.NVIC_IRQChannel = SPI1_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
        NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
        NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
        NVIC_Init(&NVIC_InitStructure);





}
void SPI1_IRQHandler(void)
{
/*  if (SPI_I2S_GetITStatus(SPI1, SPI_I2S_FLAG_TXE) == SET) {

      SPI_I2S_SendData(SPI1, (uint8_t)SPIz_Buffer_Tx[TxIdx++]);

      if(TxIdx == txBufferSize)
         TxIdx=0;
      }
*/
   if (SPI_I2S_GetFlagStatus(SPI1,SPI_I2S_FLAG_RXNE)== SET)
        SPI_SLAVE_Buffer_Rx[RxIdx++] = SPI_I2S_ReceiveData(SPI1);
    while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_BSY) == SET);

   if(RxIdx==rxBufferSize)
        RxIdx=0;

      //  SPI1_Transmit(SPIz_Buffer_Tx,SPI_SLAVE_Buffer_Rx,4);
 /* if (SPI_I2S_GetITStatus(SPI1, SPI_I2S_IT_TXE) != RESET)
  {
    //Send SPI1 data
    SPI_I2S_SendData(SPI1, SPIz_Buffer_Tx[TxIdx++]);//just an idea here as how send needs to be done

    //clear interrupt bit
  }
*/
/*  if (SPI_I2S_GetITStatus(SPI1, SPI_I2S_IT_RXNE) != RESET)
  {
    //Receive SPI1 data
   SPI_SLAVE_Buffer_Rx[RxIdx++] = SPI_I2S_ReceiveData(SPI1);


    if(RxIdx==rxBufferSize)
        RxIdx=0;//just an idea here as how receive needs to be done

    //clear interrupt bit
  }     */
}

Cuando veo la línea desde el analizador lógico, puedo ver que la línea miso siempre está en un nivel alto.