HAL_SPI_ReceiveIT not working on STM32F4

I am working on a project where I am using two boards to communicate via SPI. The master board (TMS320F28377S) is sending data successfully via SPI

Now, my receiver board is running on a STM32F439 processor, I'm relatively new to this micro. I configured it as a a Receiver Only using CubeMX, rest of settings are show below,

hspi2.Instance = SPI2;

hspi2.Init.Mode = SPI_MODE_SLAVE;

hspi2.Init.Direction = SPI_DIRECTION_2LINES_RXONLY;

hspi2.Init.DataSize = SPI_DATASIZE_8BIT;

hspi2.Init.CLKPolarity = SPI_POLARITY_LOW;

hspi2.Init.CLKPhase = SPI_PHASE_1EDGE;

hspi2.Init.NSS = SPI_NSS_HARD_INPUT; //??

//hspi2.Init.NSS = SPI_NSS_SOFT;

hspi2.Init.FirstBit = SPI_FIRSTBIT_MSB;

hspi2.Init.TIMode = SPI_TIMODE_DISABLE;

hspi2.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;

hspi2.Init.CRCPolynomial = 10;

Once the code is ready for receiving, I call the following,

if(HAL_SPI_Receive_IT(&hspi2, (uint8_t *)GEU_RX_Buffer, 2) != HAL_OK)

{

Error_Handler();

}

while(1){}

I'm placing a breakpoint in the, setting a variable and calling receive interrupt again

void HAL_SPI_RxCpltCallback(SPI_HandleTypeDef *hspi)

{

Sys_Mode = DIAGNOSTIC_MODE;

// Trigger interrupt again to keep receiving datas

HAL_SPI_Receive_IT(&hspi2, (uint8_t *)rx_buffer, 2);

}

When I make a transfer from master, I'm watching rx_buffer variable and no data is being received, also RXNE flag is not being set.

Is there something I'm missing here? All I want is to be able to receive data on another platform in non-blocking mode using interrupt. Also, should I have the NSS pin physically connected to an I/0 on the receiver micro?

Your help is appreciated in advance.

Thank you.

Gil