Sending an array to the IP core through SDK

Question

I want to send an array to the IP design through SDK rather than just a number as shown in the following code snippet. Can somebody help me in doing that? code in SDK

Answer 1

let's start saying that there are different way to send data to IP (for example from an ARM processor to a custom IP in a Zynq). Xilinx gives you the possibility to communicate using:

• AXI4 FULL interface
• AXI4 LITE interface
• AXI4 STREAM interface

Depending on the interface you use, the way to write the SDK-code running on the ARM may be quite different. There are a lot of details but in general when you create an IP, after exporting the hardware and lunching the SDK, Vivado creates library and drivers for you in order to send data and commands to the every specific IP. Just to give you an example let's say that you are using the AXI STREAM interface. Here you should add another IP (provided from Xilinx) that manage the data transfer from memory to the IP and vice versa (DMA - direct memory access). Here the code should be :

#include <stdio.h>
#include "xil_cache.h"
#include "xaxidma.h"
#include "xparameters.h"
#include "math.h"
#include "xtime_l.h"
XTime tstart,tstop;

//#define DEBUG
#define N_samples 64


int main()
{


    printf("Hello\n");
    Xil_DCacheDisable();
    Xil_ICacheDisable();
    /***************** Variables *******************/

    float input_R_IM[N_samples*2];
    float output_R_IM[N_samples*2];
    int error=-1;
    XAxiDma dma0_pointer;
    XAxiDma_Config *dma0_Config;


    /**********************DMA initialization***************************/

    dma0_Config=XAxiDma_LookupConfig(XPAR_AXIDMA_0_DEVICE_ID);
    error=XAxiDma_CfgInitialize(&dma0_pointer,dma0_Config);
#ifdef DEBUG
    if(error==XST_SUCCESS)
        printf("...initialization successful\n");
    else
        printf("**ERROR INITIALIZATION\n");
#endif
    float d = 2 * (float)M_PI / N_samples;



    size_t i=NULL;
    for (i = 0; i < N_samples; i++)
    {
        input_R_IM[i*2]=sin(0 + d*i);
        input_R_IM[i*2+1]=0;
    }

    /**********************STARTING FFT************************/
    error=-1;
    XTime_GetTime(&tstart);
    error = XAxiDma_SimpleTransfer(&dma0_pointer,(u32)input_R_IM,2*N_samples*sizeof(float),XAXIDMA_DMA_TO_DEVICE);
#ifdef DEBUG
    if(error==XST_SUCCESS)
        printf("...simply transfer 1 successful\n");
    else
        printf("**ERROR SIMPLY TRANSFER 1\n");
#endif

    /***********************COPY BACK THE RESULTS************************/
//  error=-1;
    error = XAxiDma_SimpleTransfer(&dma0_pointer,(u32)output_R_IM,2*N_samples*sizeof(float),XAXIDMA_DEVICE_TO_DMA);
#ifdef DEBUG
    if(error==XST_SUCCESS)
        printf("...simply transfer 2 successful\n");
    else
        printf("**ERROR SIMPLY TRANSFER 2\n");
#endif
    XTime_GetTime(&tstop);
    u64 cycles = tstop-tstart;
    float t = ((float)cycles / COUNTS_PER_SECOND)*1000000;
    printf("cycles= %lld (time = %f us)\n",cycles,t);

    for (i = 0; i < N_samples; i++)
    {
        printf("i: %d real=> %f  --imag==> %f \n" ,i, output_R_IM[i*2], output_R_IM[i*2+1]);
    }

    printf("Goodbye\n");
    return 0;
}

This is an old code used to send data from one of the ARM processor to the FFT IP using and AXI-DMA.

Here you can find an AXI reference Guide in order to have a better idea on how to manage the data between IP on Xilinx FPGA