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SAbde7
Beginner
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How to read an on-chip fifo using PCIE_DmaRead()

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I am trying to transfer data between a PC and an FPGA. I am using C++ for the computer program and the FPGA is a Stratix V. On the FPGA, I need to use FIFOs to buffer recieved data and data about to be sent.On the FPGA I am using a PCIE example design from the user CD of the DE5-net kit.

 

I have managed to write to- and read from- an on chip fifo using PCIE_Write32() and PCIE_Read32(). The user Manual states, however, that these functions are not appropriate for continuous, large data transfers and that PCIE_DmaRead()/PCIE_DmaWrite() should be used instead.

 

I tried Writing data to the FIFO using PCIE_DmaWrite() and it worked, as I verified by reading the written values with PCIE_Read32(). My problem is that I cannot get PCIE_DmaRead() to work. Whenever I call it it returns a random(but fixed) value, and does not pop anything from the FIFO(doesn't reduce the fill level).

 

am I doing something wrong or is it only possible to write to, but not read from, FIFOs by using the DMA functions?

here are my code and my design:

 

image.png

 

---------------------

#include "stdafx.h"

 

#include <stdio.h>

#include <stdlib.h>

#include <memory.h>

#include "PCIE.h"

 

 

#define DEMO_PCIE_USER_BAR PCIE_BAR4

#define DEMO_PCIE_IO_LED_ADDR 0x4000010

#define DEMO_PCIE_IO_BUTTON_ADDR 0x4000020

#define DEMO_PCIE_ONCHIP_MEM_ADDR 0x00000000

#define DEMO_PCIE_DDR3A_MEM_ADDR 0x100000000

#define DEMO_PCIE_DDR3B_MEM_ADDR 0x200000000

#define FIFO_WRITE_MEM_ADDR     0x90000

#define FIFO_READ_MEM_ADDR     0x90004

 

#define ONCHIP_MEM_TEST_SIZE (512*1024) //512KB

#define DDR3A_MEM_TEST_SIZE    (2*1024*1024*1024) //2GB

#define DDR3B_MEM_TEST_SIZE   (2*1024*1024*1024) //2GB

 

...

 

BOOL TEST_DMA_WRITE(PCIE_HANDLE hPCIe) {

BOOL bPass;

int push[10];

int number;

 

do

{

printf("Please input number of integers to write:");

scanf("%d", &number);

 

} while (number < 0 || number > 10);

 

for (int i = 0; i < number; i++)

{

printf("Please input fifo data:");

scanf("%d", push + i);

}

 

 

bPass = PCIE_DmaWrite(hPCIe, FIFO_WRITE_MEM_ADDR, push, number*sizeof(int));

 

if (bPass)

printf("write success, data=%d\r\n", push[0]);

else

printf("write failed\r\n");

 

 

return bPass;

}

 

BOOL TEST_DMA_READ(PCIE_HANDLE hPCIe) { //doesn't work !!!

BOOL bPass = TRUE;

int Status[10];

int number;

 

do

{

printf("Please input number of integers to read:");

scanf("%d", &number);

 

} while (number < 0 || number > 10);

 

bPass = PCIE_DmaRead(hPCIe, FIFO_READ_MEM_ADDR, Status, number * sizeof(int));

 

if (bPass)

{

for (int i = 0; i < number; i++)

{

printf("data read:=%d\r\n", Status[i]);

}

}

else

{

printf("Failed to read data\r\n");

}

 

return bPass;

}

 

-----------------------------------------------

 

 

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1 Solution
BoonT_Intel
Moderator
106 Views

Hi Sir,

Theoretically, DMA function is not work for FIFOs but it is only work for memory that have physical address. FIFO unlike a memory (DDR3) and no address associate with it. Thus, for FIFO, we usually used write/read32.

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1 Reply
BoonT_Intel
Moderator
107 Views

Hi Sir,

Theoretically, DMA function is not work for FIFOs but it is only work for memory that have physical address. FIFO unlike a memory (DDR3) and no address associate with it. Thus, for FIFO, we usually used write/read32.

View solution in original post

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