SPI communication between FPGA(as a slave) and microcontroller(as master)

/***************************** Include Files *********************************/

#include "xparameters.h" /* XPAR parameters */
#include "xspi.h" /* SPI device driver */
#include "stdio.h"
#include "xil_printf.h"

/************************** Constant Definitions *****************************/

/*
* The following constants map to the XPAR parameters created in the
* xparameters.h file. They are defined here such that a user can easily
* change all the needed parameters in one place.
*/
#define SPI_DEVICE_ID XPAR_SPI_0_DEVICE_ID

/*
* This is the size of the buffer to be transmitted/received in this example.
*/
#define BUFFER_SIZE 16

/**************************** Type Definitions *******************************/


/***************** Macros (Inline Functions) Definitions *********************/


/************************** Function Prototypes ******************************/

static int SpiSlavePolledExample(XSpi *SpiInstancePtr, u16 SpiDeviceId);

/************************** Variable Definitions *****************************/

/*
* The instances to support the device drivers are global such that they are
* initialized to zero each time the program runs. They could be local but
* should at least be static so that they are zeroed.
*/
static XSpi SpiInstance; /* The instance of the SPI device */

/*
* The following variables are used to read from the Spi device, these are
* global to avoid having large buffers on the stack.
*/
u8 ReadBuffer[BUFFER_SIZE];
u8 WriteBuffer[BUFFER_SIZE];

/*
* The following variable allows a test value to be added to the values that
* are sent in reflection to the Master transmission such that unique values can
* be generated to guarantee the transfer from Slave to Master is successful.
*/
int Test;

/*****************************************************************************/
/**
*
* Main function to call the Spi Slave example in polled mode.
*
* [USER=42587]@param[/USER] None
*
* [USER=344527]@Return[/USER] XST_SUCCESS if successful, otherwise XST_FAILURE.
*
* [USER=545121]@note[/USER] None
*
******************************************************************************/
int main(void)
{
int Status;

/*
* Run the Spi Slave polled example.
*/
Status = SpiSlavePolledExample(&SpiInstance, SPI_DEVICE_ID);
if (Status != XST_SUCCESS) {
xil_printf("Spi slave polled Example Failed\r\n");
return XST_FAILURE;
}

xil_printf("Successfully ran Spi slave polled Example\r\n");
return XST_SUCCESS;
}

/*****************************************************************************/
/**
*
* This function does a minimal test on the Spi device and driver as a design
* example. The purpose of this function is to illustrate the device slave
* functionality in polled mode. This function receives data from a master and
* prints the received data.
*
* [USER=42587]@param[/USER] SpiInstancePtr is a pointer to the instance of Spi component.
*
* [USER=42587]@param[/USER] SpiDeviceId is the Device ID of the Spi Device and is the
* XPAR_<SPI_instance>_DEVICE_ID value from xparameters.h.
*
* [USER=344527]@Return[/USER] XST_SUCCESS if successful, otherwise XST_FAILURE.
*
* [USER=545121]@note[/USER] This function contains an infinite loop such that if the Spi
* device doesn't receive any data, it may never return.
*
******************************************************************************/
int SpiSlavePolledExample(XSpi *SpiInstancePtr, u16 SpiDeviceId)
{
XSpi_Config *ConfigPtr;
int Status;
u32 Count;

xil_printf("\r\nEntering the Spi Slave Polled Example.\r\n");
xil_printf("Waiting for data from SPI master\r\n");

/*
* Initialize the SPI driver so that it's ready to use, specify the
* device ID that is generated in xparameters.h.
*/
ConfigPtr = XSpi_LookupConfig(SpiDeviceId);
if (ConfigPtr == NULL) {
return XST_FAILURE;
}
Status = XSpi_CfgInitialize(SpiInstancePtr, ConfigPtr,
ConfigPtr->BaseAddress);
if (Status != XST_SUCCESS) {
return XST_FAILURE;
}

/*
* The SPI device is a slave by default and the clock phase and polarity
* have to be set according to its master. In this example, CPOL is set
* to active low and CPHA is set to 1.
*/
Status = XSpi_SetOptions(SpiInstancePtr,
XSP_CLK_ACTIVE_LOW_OPTION | XSP_CLK_PHASE_1_OPTION);
if (Status != XST_SUCCESS) {
return XST_FAILURE;
}

/*
* Start the SPI driver so that the device is enabled.
*/
XSpi_Start(SpiInstancePtr);

/*
* Disable Global interrupt to use polled mode operation.
*/
XSpi_IntrGlobalDisable(SpiInstancePtr);


/*
* Initialize the write buffer with pattern to write, initialize the
* read buffer to zero so that it can be verified after the read.
*/
//Test = 0xF0;
//for (Count = 0; Count < BUFFER_SIZE; Count++) {
//WriteBuffer[Count] = (u8)(Count + Test);
//ReadBuffer[Count] = 0;
//}

/*
* Prepare the data buffers for transmission and to send/receive data
* when the SPI device is selected by a master.
*/
XSpi_Transfer(SpiInstancePtr, WriteBuffer, ReadBuffer, BUFFER_SIZE);

/*
* Print all the data received from the master so that it can be
* compared with the data sent by the master.
*/
xil_printf("\r\nReceived data is:\r\n");
for (Count = 0; Count < BUFFER_SIZE; Count++) {
xil_printf("0x%x \r\n", ReadBuffer[Count]);
}

xil_printf("\r\nExiting the Spi Slave Polled Example.\r\n");

return XST_SUCCESS;
}